Half Moon Bay Airport WX RSS feed

Area Forecast Discussion

FXUS66 KMTR [Monterey CA] 171732 AFDMTR ∨

FXUS66 KMTR 171732
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 9:32am PST Sun Jan 17 2021 ∨

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
932 AM PST SUN JAN 17 2021 [HEAD]

Synopsis. Warm, dry weather continues as high pressure lingers over the Pacific Ocean to our west. Two back to back low pressure systems to our east will produce breezy to gusty offshore flow tonight through Tuesday evening. Cooling trend is forecast from Wednesday through Friday. ∨

.SYNOPSIS...WARM, DRY WEATHER CONTINUES AS HIGH PRESSURE LINGERS
OVER THE PACIFIC OCEAN TO OUR WEST. TWO BACK TO BACK LOW PRESSURE
SYSTEMS TO OUR EAST WILL PRODUCE BREEZY TO GUSTY OFFSHORE FLOW
TONIGHT THROUGH TUESDAY EVENING. COOLING TREND IS FORECAST FROM
WEDNESDAY THROUGH FRIDAY. [DISC]

Discussion. As of 08:36am PST Sunday… a warm start to the day this morning across much of central California and have observed a slight marine layer signature this morning along our immediate coast (akin to what we would normally observe during the summer)as well. Have observed temps across the Bay Area and immediate Central Coast currently ranging between 45–55°F and temps while temps at elevated interior are running a few degrees warmer (~55–65°F)as a result. Upper-level ridge is also set in place through the afternoon, so are looking at another warm day today across the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map], with widespread Max temps in the upper 60s to low 70s F. Please refer to the climate section for today's list of record highs. Switching gears over to our winds, observed breezy conditions along the foothills overnight, with the Oakland Hills north observation at one point measuring sustained NNE winds of 20 mph and a gust of 30 mph. Values were much more pronounced at some of our highest peaks, with Mt Diablo and MT.St Helena reporting gusts over 65 mph between 2 and 3am this morning. The morning Fort Ord and bodega profilers are both picking up on the offshore, NNE winds aloft.these offshore NE winds will become more apparent later this afternoon and evening as these winds from aloft mix down to lower elevations. Be mindful and prepare in advance for windy conditions across the region beginning this evening. ∨

.DISCUSSION...AS OF 08:36 AM PST SUNDAY...A WARM START TO THE DAY THIS
MORNING ACROSS MUCH OF CENTRAL CALIFORNIA AND HAVE OBSERVED A SLIGHT
MARINE LAYER SIGNATURE THIS MORNING ALONG OUR IMMEDIATE COAST(AKIN
TO WHAT WE WOULD NORMALLY OBSERVE DURING THE SUMMER)AS WELL. HAVE
OBSERVED TEMPS ACROSS THE BAY AREA AND IMMEDIATE CENTRAL COAST
CURRENTLY RANGING BETWEEN 45-55 F AND TEMPS WHILE TEMPS AT ELEVATED
INTERIOR ARE RUNNING A FEW DEGREES WARMER (~55-65F)AS A RESULT.
UPPER-LEVEL RIDGE IS ALSO SET IN PLACE THROUGH THE AFTERNOON, SO ARE
LOOKING AT ANOTHER WARM DAY TODAY ACROSS THE CWA, WITH WIDESPREAD
MAX TEMPS IN THE UPPER 60S TO LOW 70S F. PLEASE REFER TO THE CLIMATE
SECTION FOR TODAY`S LIST OF RECORD HIGHS. SWITCHING GEARS OVER TO
OUR WINDS, OBSERVED BREEZY CONDITIONS ALONG THE FOOTHILLS OVERNIGHT,
WITH THE OAKLAND HILLS NORTH OB AT ONE POINT MEASURING SUSTAINED NNE
WINDS OF 20MPH AND A GUST OF 30MPH. VALUES WERE MUCH MORE PRONOUNCED
AT SOME OF OUR HIGHEST PEAKS, WITH MT. DIABLO AND MT.ST. HELENA
REPORTING GUSTS OVER 65MPH BETWEEN 2 AND 3AM THIS MORNING. THE
MORNING FT. ORD AND BODEGA PROFILERS ARE BOTH PICKING UP ON THE
OFFSHORE, NNE WINDS ALOFT.THESE OFFSHORE NE WINDS WILL BECOME MORE
APPARENT LATER THIS AFTERNOON AND EVENING AS THESE WINDS FROM ALOFT
MIX DOWN TO LOWER ELEVATIONS. BE MINDFUL AND PREPARE IN ADVANCE FOR
WINDY CONDITIONS ACROSS THE REGION BEGINNING THIS EVENING. [DISC]

Previous discussion… as of 03:30am PST Sunday. One more day of fairly calm, sunny, and warm weather before our strong offshore wind event impacts the region late tonight into Tuesday. Daytime highs will range from the mid 60s to the upper 70s this afternoon and we may be near or break a few more records. The sites where our current forecast is close to the record include: Santa Rosa, Kentfield, Napa, Livermore, and SFO [San Francisco CA]. ∨

.PREV DISCUSSION...AS OF 03:30 AM PST SUNDAY...ONE MORE DAY OF FAIRLY
CALM, SUNNY, AND WARM WEATHER BEFORE OUR STRONG OFFSHORE WIND
EVENT IMPACTS THE REGION LATE TONIGHT INTO TUESDAY. DAYTIME HIGHS
WILL RANGE FROM THE MID 60S TO THE UPPER 70S THIS AFTERNOON AND WE
MAY BE NEAR OR BREAK A FEW MORE RECORDS. THE SITES WHERE OUR
CURRENT FORECAST IS CLOSE TO THE RECORD INCLUDE: SANTA ROSA,
KENTFIELD, NAPA, LIVERMORE, AND SFO. [DISC]

The offshore wind event continues to look strong so use today as an opportunity to prepare. In case of power outages: make sure cell phones/devices are fully charged, gather up flashlights and extra batteries, and have a supply of non-perishable food/water. If there are widespread power outages, remember that it may take crews longer to get the power back on so make sure you have what you need in case you have to go a day or two without power. Other things to remember: secure loose outdoor objects, trim dead tree branches on your property, be cautious when driving as occasionally strong gusts may suddenly hit your vehicle. ∨

THE OFFSHORE WIND EVENT CONTINUES TO LOOK STRONG SO USE TODAY AS
AN OPPORTUNITY TO PREPARE. IN CASE OF POWER OUTAGES: MAKE SURE
CELL PHONES/DEVICES ARE FULLY CHARGED, GATHER UP FLASHLIGHTS AND
EXTRA BATTERIES, AND HAVE A SUPPLY OF NON-PERISHABLE FOOD/WATER.
IF THERE ARE WIDESPREAD POWER OUTAGES, REMEMBER THAT IT MAY TAKE
CREWS LONGER TO GET THE POWER BACK ON SO MAKE SURE YOU HAVE WHAT
YOU NEED IN CASE YOU HAVE TO GO A DAY OR TWO WITHOUT POWER. OTHER
THINGS TO REMEMBER: SECURE LOOSE OUTDOOR OBJECTS, TRIM DEAD TREE
BRANCHES ON YOUR PROPERTY, BE CAUTIOUS WHEN DRIVING AS
OCCASIONALLY STRONG GUSTS MAY SUDDENLY HIT YOUR VEHICLE. [DISC]

This offshore event is still set up to arrive in two waves as two lows slide southward to our east. The first one arrives late tonight starting over the North and East Bay hills then downsloping into portions of the valley and spreading across SF Bay Area early Monday morning into Monday afternoon. In fact, we're already seeing hints of the offshore pressure gradient setting up. One of our higher exposed peaks is Mt Diablo and it is already experiencing the increased upper level winds due to its elevation. It has had gusts over 50 mph with a few Max gusts around 70 since midnight. Those enhanced winds will gradually mix down impacting the rest of the North and East Bay terrain tonight. The SFO [San Francisco CA]-Winnemucca [NW Nevada] pressure gradient is a good indication of the intensity of these offshore events and GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] shows a –10 to –13 mb difference for this first wave which is a solid event given that we start paying attention at a –7 mb difference. ∨

THIS OFFSHORE EVENT IS STILL SET UP TO ARRIVE IN TWO WAVES AS TWO
LOWS SLIDE SOUTHWARD TO OUR EAST. THE FIRST ONE ARRIVES LATE
TONIGHT STARTING OVER THE NORTH AND EAST BAY HILLS THEN
DOWNSLOPING INTO PORTIONS OF THE VALLEY AND SPREADING ACROSS SF
BAY AREA EARLY MONDAY MORNING INTO MONDAY AFTERNOON. IN FACT,
WE`RE ALREADY SEEING HINTS OF THE OFFSHORE PRESSURE GRADIENT
SETTING UP. ONE OF OUR HIGHER EXPOSED PEAKS IS MT DIABLO AND IT IS
ALREADY EXPERIENCING THE INCREASED UPPER LEVEL WINDS DUE TO ITS
ELEVATION. IT HAS HAD GUSTS OVER 50 MPH WITH A FEW MAX GUSTS
AROUND 70 SINCE MIDNIGHT. THOSE ENHANCED WINDS WILL GRADUALLY MIX
DOWN IMPACTING THE REST OF THE NORTH AND EAST BAY TERRAIN TONIGHT.
THE SFO-WMC PRESSURE GRADIENT IS A GOOD INDICATION OF THE
INTENSITY OF THESE OFFSHORE EVENTS AND GFS SHOWS A -10 TO -13 MB
DIFFERENCE FOR THIS FIRST WAVE WHICH IS A SOLID EVENT GIVEN THAT
WE START PAYING ATTENTION AT A -7 MB DIFFERENCE. [DISC]

The second and stronger wave arrives Monday night into Tuesday with winds peaking 10pm Monday to 10am Tuesday. For comparison, the GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] has the SFO [San Francisco CA]-Winnemucca [NW Nevada] pressure gradient ranging from –13 to –19 mb. This second wave also impacts the majority of our CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map] as gusty conditions spread southward down to Monterey and San Benito Counties. It's plausible that this second wave might be upgraded to a High Wind Warning if high-resolution models remain consistent with stronger gusts and enhance fire weather concerns. Keeping the summary of this event below as it covers the wind speeds and discusses fire weather concerns: ∨

THE SECOND AND STRONGER WAVE ARRIVES MONDAY NIGHT INTO TUESDAY
WITH WINDS PEAKING 10 PM MON TO 10 AM TUES. FOR COMPARISON, THE
GFS HAS THE SFO-WMC PRESSURE GRADIENT RANGING FROM -13 TO -19 MB.
THIS SECOND WAVE ALSO IMPACTS THE MAJORITY OF OUR CWA AS GUSTY
CONDITIONS SPREAD SOUTHWARD DOWN TO MONTEREY AND SAN BENITO
COUNTIES. IT`S PLAUSIBLE THAT THIS SECOND WAVE MIGHT BE UPGRADED
TO A HIGH WIND WARNING IF HI-RES MODELS REMAIN CONSISTENT WITH
STRONGER GUSTS AND ENHANCE FIRE WEATHER CONCERNS. KEEPING THE
SUMMARY OF THIS EVENT BELOW AS IT COVERS THE WIND SPEEDS AND
DISCUSSES FIRE WEATHER CONCERNS: [DISC]

Two pieces to cover. 1) the wind itself. Sustained winds are forecast to be in the 5–20 mph range though populated areas, with the exact value being location dependent. Sustained winds in the hills and mountains are forecast to be in the 15–30 mph range. However, in events like this, it's the gusts that really do the damage. Occasional gusts in valley populated locations could be in the 20–45 mph range, again depending upon location. While in the hills and mountains, expect to see maximum gusts reach 45–60 mph range with the possibility of an isolated site or two trying to jump into the 70+ arena. Branches are dry and brittle in many areas which means they are prone to break and fall, while trees may simply topple in some of the stronger gusts. Please know your risk. Wind statistically is the second leading cause of death due in our area due to falling trees. 2) while we have seen a little rain this winter, it hasn't been a lot and most areas are running about 30% of average on the water year thus far. The rain has helped the larger trees (fuels) to get some moisture in them. However, the fine fuels such as grasses and bushes moisten up quickly and dry out quickly. With the dry warm weather the last few days, it has dried the finer fuels. We have dry grasses, gusty winds coming, and plummeting relative humidities. Since the larger fuels still have moisture, we are not thinking of a Red Flag Warning at this point, but will be watching closely each shift to analyze incoming data. In short, fire concerns exist. Be fire smart, don't be that spark. ∨

TWO PIECES TO COVER. 1) THE WIND ITSELF. SUSTAINED WINDS ARE
FORECAST TO BE IN THE 5 TO 20 MPH RANGE THOUGH POPULATED AREAS,
WITH THE EXACT VALUE BEING LOCATION DEPENDENT. SUSTAINED WINDS IN
THE HILLS AND MOUNTAINS ARE FORECAST TO BE IN THE 15 TO 30 MPH
RANGE. HOWEVER, IN EVENTS LIKE THIS, IT`S THE GUSTS THAT REALLY DO
THE DAMAGE. OCCASIONAL GUSTS IN VALLEY POPULATED LOCATIONS COULD
BE IN THE 20 TO 45 MPH RANGE, AGAIN DEPENDING UPON LOCATION. WHILE
IN THE HILLS AND MOUNTAINS, EXPECT TO SEE MAXIMUM GUSTS REACH 45
TO 60 MPH RANGE WITH THE POSSIBILITY OF AN ISOLATED SITE OR TWO
TRYING TO JUMP INTO THE 70+ ARENA. BRANCHES ARE DRY AND BRITTLE
IN MANY AREAS WHICH MEANS THEY ARE PRONE TO BREAK AND FALL, WHILE
TREES MAY SIMPLY TOPPLE IN SOME OF THE STRONGER GUSTS. PLEASE KNOW
YOUR RISK. WIND STATISTICALLY IS THE SECOND LEADING CAUSE OF
DEATH DUE IN OUR AREA DUE TO FALLING TREES. 2) WHILE WE HAVE SEEN
A LITTLE RAIN THIS WINTER, IT HASN`T BEEN A LOT AND MOST AREAS ARE
RUNNING ABOUT 30% OF AVERAGE ON THE WATER YEAR THUS FAR. THE RAIN
HAS HELPED THE LARGER TREES (FUELS) TO GET SOME MOISTURE IN THEM.
HOWEVER, THE FINE FUELS SUCH AS GRASSES AND BUSHES MOISTEN UP
QUICKLY AND DRY OUT QUICKLY. WITH THE DRY WARM WEATHER THE LAST
FEW DAYS, IT HAS DRIED THE FINER FUELS. WE HAVE DRY GRASSES,
GUSTY WINDS COMING, AND PLUMMETING RELATIVE HUMIDITIES. SINCE THE
LARGER FUELS STILL HAVE MOISTURE, WE ARE NOT THINKING OF A RED
FLAG WARNING AT THIS POINT, BUT WILL BE WATCHING CLOSELY EACH
SHIFT TO ANALYZE INCOMING DATA. IN SHORT, FIRE CONCERNS EXIST. BE
FIRE SMART, DON`T BE THAT SPARK. [DISC]

Breezy offshore conditions could linger into Wednesday morning but taper off in the afternoon. Highs for Wednesday are forecast to remain well above average with most areas seeing highs in the upper 60s. Wednesday looks to continue the trend of dry and clear skies, but that will likely change the following day. ∨

BREEZY OFFSHORE CONDITIONS COULD LINGER INTO WEDNESDAY MORNING BUT
TAPER OFF IN THE AFTERNOON. HIGHS FOR WEDNESDAY ARE FORECAST TO
REMAIN WELL ABOVE AVERAGE WITH MOST AREAS SEEING HIGHS IN THE
UPPER 60S. WEDNESDAY LOOKS TO CONTINUE THE TREND OF DRY AND CLEAR
SKIES, BUT THAT WILL LIKELY CHANGE THE FOLLOWING DAY. [DISC]

Thursday offers quite a change to the pattern as winds shift to an onshore flow as low pressure moves into Northern California. This will initiate a cooling trend to start on Thursday with highs still slightly above average, just more focused around the 60° mark. The GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] and ECMWF [European Center for Medium-Range Weather Forecasts model] agree on the onshore flow, but disagree on moisture and how westerly the winds will get. The GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] is optimistic for rain chances and more westerly winds, while the national blend and the ECMWF [European Center for Medium-Range Weather Forecasts model] are only offering slight chances and winds from the northwest. Models and ensembles are placing their initial rain chances into Thursday night, but the GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] wants these chances to last much longer. The GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] continues the chances for light rain into the weekend, but not many other forecasts are being so bold. Regardless, what rain does fall during this time looks to only fall at mild rates. ∨

THURSDAY OFFERS QUITE A CHANGE TO THE PATTERN AS WINDS SHIFT TO
AN ONSHORE FLOW AS LOW PRESSURE MOVES INTO NORTHERN CALIFORNIA.
THIS WILL INITIATE A COOLING TREND TO START ON THURSDAY WITH
HIGHS STILL SLIGHTLY ABOVE AVERAGE, JUST MORE FOCUSED AROUND THE
60 DEGREE MARK. THE GFS AND ECMWF AGREE ON THE ONSHORE FLOW, BUT
DISAGREE ON MOISTURE AND HOW WESTERLY THE WINDS WILL GET. THE GFS
IS OPTIMISTIC FOR RAIN CHANCES AND MORE WESTERLY WINDS, WHILE THE
NATIONAL BLEND AND THE ECMWF ARE ONLY OFFERING SLIGHT CHANCES AND
WINDS FROM THE NORTHWEST. MODELS AND ENSEMBLES ARE PLACING THEIR
INITIAL RAIN CHANCES INTO THURSDAY NIGHT, BUT THE GFS WANTS THESE
CHANCES TO LAST MUCH LONGER. THE GFS CONTINUES THE CHANCES FOR
LIGHT RAIN INTO THE WEEKEND, BUT NOT MANY OTHER FORECASTS ARE
BEING SO BOLD. REGARDLESS, WHAT RAIN DOES FALL DURING THIS TIME
LOOKS TO ONLY FALL AT MILD RATES. [DISC]

Despite the rain disagreement, models show the cooling trend continuing into the weekend. Near average highs are expected for the tail end of the forecast. Some areas could start seeing below average overnight lows. A few interior areas could even see freezing temperatures to start Saturday and Sunday, but this could be limited by how much moisture is in the region. ∨

DESPITE THE RAIN DISAGREEMENT, MODELS SHOW THE COOLING TREND
CONTINUING INTO THE WEEKEND. NEAR AVERAGE HIGHS ARE EXPECTED FOR
THE TAIL END OF THE FORECAST. SOME AREAS COULD START SEEING BELOW
AVERAGE OVERNIGHT LOWS. A FEW INTERIOR AREAS COULD EVEN SEE
FREEZING TEMPERATURES TO START SATURDAY AND SUNDAY, BUT THIS COULD
BE LIMITED BY HOW MUCH MOISTURE IS IN THE REGION. [DISC]

Aviation. As of 09:32am PST Sunday… for the 18Z [10am PST] TAFs [Terminal Aerodrome Forecasts]. Widespread VFR [Visual Flight Rules] conditions as breezy offshore winds persist across the higher elevations. VFR [Visual Flight Rules] conditions to prevail through the period with patchy fog possible late this evening around KMRY [Monterey CA] and KSNS [Salinas CA]. Offshore winds aloft will diminish into this afternoon before increasing again late tonight. Low-level wind shear will become an issue starting late tonight with winds at 1500–2000 ft at around 30–35 kt [35–40 mph] near many of the North Bay and Bay Area terminals. Gusts will start to mix down to the surface towards the end of the TAF [Terminal Aerodrome Forecast] period. An additional round of stronger and more widespread offshore winds is expected tomorrow night with strong surface gusts also anticipated. ∨

.AVIATION...AS OF 09:32 AM PST SUNDAY...FOR THE 18Z TAFS. WIDESPREAD
VFR CONDITIONS AS BREEZY OFFSHORE WINDS PERSIST ACROSS THE HIGHER
ELEVATIONS. VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD WITH
PATCHY FOG POSSIBLE LATE THIS EVENING AROUND KMRY AND KSNS.
OFFSHORE WINDS ALOFT WILL DIMINISH INTO THIS AFTERNOON BEFORE
INCREASING AGAIN LATE TONIGHT. LLWS WILL BECOME AN ISSUE STARTING
LATE TONIGHT WITH WINDS AT 1500 TO 2000 FT AT AROUND 30 TO 35 KT
NEAR MANY OF THE NORTH BAY AND BAY AREA TERMINALS. GUSTS WILL
START TO MIX DOWN TO THE SURFACE TOWARDS THE END OF THE TAF
PERIOD. AN ADDITIONAL ROUND OF STRONGER AND MORE WIDESPREAD
OFFSHORE WINDS IS EXPECTED TOMORROW NIGHT WITH STRONG SURFACE
GUSTS ALSO ANTICIPATED. [AVIA]

Vicinity of KSFO [San Francisco CA]… VFR [Visual Flight Rules] with some passing high clouds. Light winds this morning with diminishing low-level wind shear into this afternoon. Onshore winds this afternoon around 10–15 kt [12–17 mph]. Increasing offshore winds aloft tonight will generate low-level wind shear concerns through the rest of the TAF [Terminal Aerodrome Forecast] period. Stronger offshore winds expected tomorrow night. ∨

VICINITY OF KSFO...VFR WITH SOME PASSING HIGH CLOUDS. LIGHT WINDS
THIS MORNING WITH DIMINISHING LLWS INTO THIS AFTERNOON. ONSHORE
WINDS THIS AFTERNOON AROUND 10 TO 15 KT. INCREASING OFFSHORE WINDS
ALOFT TONIGHT WILL GENERATE LLWS CONCERNS THROUGH THE REST OF THE
TAF PERIOD. STRONGER OFFSHORE WINDS EXPECTED TOMORROW NIGHT. [AVI2]

SFO [San Francisco CA] bridge approach… similar to KSFO [San Francisco CA]. ∨

SFO BRIDGE APPROACH...SIMILAR TO KSFO. [AVI2]

Monterey Bay terminals… VFR [Visual Flight Rules]. Light winds this morning turning NW this afternoon. May see some patchy fog again late this evening but should mix out overnight. ∨

MONTEREY BAY TERMINALS...VFR. LIGHT WINDS THIS MORNING TURNING NW
THIS AFTERNOON. MAY SEE SOME PATCHY FOG AGAIN LATE THIS EVENING
BUT SHOULD MIX OUT OVERNIGHT. [AVI2]

Beaches… as of 04:05am PST Sunday… a large, very long period northwest swell will arrive this morning and result in hazardous conditions along the coast today through Monday afternoon. Forerunners are expected to arrive at 3–7 feet with a period of 22–24 seconds through this morning, increasing the risk of sneaker waves. Swell heights are then expected to build later Sunday into Monday with breaking waves of 18–22 feet, locally higher at favored breakpoints, expected along west to northwest facing beaches. As a result, a High Surf Advisory is in effect through Monday afternoon for west and northwest facing beaches while a beach hazard statement has been issued for the northern Monterey Bay including Santa Cruz. With unseasonably warm temperatures this holiday weekend, it will likely attract more people to the coast. Individuals should be reminded that our coastline and the cold Pacific waters remain dangerous as these larger than normal waves impact the coast. Extreme caution is advised when visiting area beaches. Never turn your back to the ocean. ∨

.BEACHES...AS OF 04:05 AM PST SUNDAY...A LARGE, VERY LONG PERIOD
NORTHWEST SWELL WILL ARRIVE THIS MORNING AND RESULT IN HAZARDOUS
CONDITIONS ALONG THE COAST TODAY THROUGH MONDAY AFTERNOON.
FORERUNNERS ARE EXPECTED TO ARRIVE AT 3 TO 7 FEET WITH A PERIOD OF
22 TO 24 SECONDS THROUGH THIS MORNING, INCREASING THE RISK OF
SNEAKER WAVES. SWELL HEIGHTS ARE THEN EXPECTED TO BUILD LATER
SUNDAY INTO MONDAY WITH BREAKING WAVES OF 18 TO 22 FEET, LOCALLY
HIGHER AT FAVORED BREAKPOINTS, EXPECTED ALONG WEST TO NORTHWEST
FACING BEACHES. AS A RESULT, A HIGH SURF ADVISORY IS IN EFFECT
THROUGH MONDAY AFTERNOON FOR WEST AND NORTHWEST FACING BEACHES
WHILE A BEACH HAZARD STATEMENT HAS BEEN ISSUED FOR THE NORTHERN
MONTEREY BAY INCLUDING SANTA CRUZ. WITH UNSEASONABLY WARM
TEMPERATURES THIS HOLIDAY WEEKEND, IT WILL LIKELY ATTRACT MORE
PEOPLE TO THE COAST. INDIVIDUALS SHOULD BE REMINDED THAT OUR
COASTLINE AND THE COLD PACIFIC WATERS REMAIN DANGEROUS AS THESE
LARGER THAN NORMAL WAVES IMPACT THE COAST. EXTREME CAUTION IS
ADVISED WHEN VISITING AREA BEACHES. NEVER TURN YOUR BACK TO THE
OCEAN. [DISC]

Climate. Record type: highs (old record temp/year) ∨

.CLIMATE...RECORD TYPE: HIGHS (OLD RECORD TEMP/YEAR) [AVIA]

                    Jan 17th    Jan 18th ∨

                    JAN 17TH    JAN 18TH [POPS]

Santa Rosa          71/1991     74/1976
Kentfield           71/1994     70/2014
Napa                72/1920     76/1920
Richmond            73/2009     71/2018
Livermore           70/1986     74/1919
San Francisco       73/1991     70/1920
SFO                 70/1991     68/1948
Redwood City        77/1948     74/2009
Half Moon Bay       75/2009     72/2009
Oakland downtown    74/2014     73/2014
San Jose            76/1920     74/1920
Gilroy              77/2014     80/2014*
Santa Cruz          83/2014     83/1920
Salinas Airport     86/2014*    81/1994
King City           86/2014*    83/2009 ∨

SANTA ROSA          71/1991     74/1976
KENTFIELD           71/1994     70/2014
NAPA                72/1920     76/1920
RICHMOND            73/2009     71/2018
LIVERMORE           70/1986     74/1919
SAN FRANCISCO       73/1991     70/1920
SFO                 70/1991     68/1948
REDWOOD CITY        77/1948     74/2009
HALF MOON BAY       75/2009     72/2009
OAKLAND DOWNTOWN    74/2014     73/2014
SAN JOSE            76/1920     74/1920
GILROY              77/2014     80/2014*
SANTA CRUZ          83/2014     83/1920
SALINAS AIRPORT     86/2014*    81/1994
KING CITY           86/2014*    83/2009 [POPS]

*monthly records ∨

*MONTHLY RECORDS [DISC]

Marine. As of 08:22am PST Sunday… moderate to locally strong north to northwest winds will prevail over the waters today. The strongest winds are expected over the northern outer waters where occasional low end gale-force gusts will be possible. Locally breezy conditions will also be present along the Big Sur coast south of Point Sur [Big Sur CA]. These winds will persist into tomorrow before a burst of offshore winds over land spills over into the waters starting tomorrow night. This will bring gale force conditions across the nearshore waters and through portions of the San Francisco Bay into mid-week. A large, very long period northwest swell will arrive today and persist through late tomorrow bringing additional hazards for small crafts. ∨

.MARINE...AS OF 08:22 AM PST SUNDAY...MODERATE TO LOCALLY STRONG
NORTH TO NORTHWEST WINDS WILL PREVAIL OVER THE WATERS TODAY. THE
STRONGEST WINDS ARE EXPECTED OVER THE NORTHERN OUTER WATERS WHERE
OCCASIONAL LOW END GALE-FORCE GUSTS WILL BE POSSIBLE. LOCALLY
BREEZY CONDITIONS WILL ALSO BE PRESENT ALONG THE BIG SUR COAST
SOUTH OF POINT SUR. THESE WINDS WILL PERSIST INTO TOMORROW BEFORE
A BURST OF OFFSHORE WINDS OVER LAND SPILLS OVER INTO THE WATERS
STARTING TOMORROW NIGHT. THIS WILL BRING GALE FORCE CONDITIONS
ACROSS THE NEARSHORE WATERS AND THROUGH PORTIONS OF THE SAN
FRANCISCO BAY INTO MID-WEEK. A LARGE, VERY LONG PERIOD NORTHWEST
SWELL WILL ARRIVE TODAY AND PERSIST THROUGH LATE TOMORROW BRINGING
ADDITIONAL HAZARDS FOR SMALL CRAFTS. [AVIA]

MTR Watches/Warnings/Advisories

Today: High Surf Advisory…CAZ006–505–509–530 Small Craft Advisory…Pt Arena [Mendocino CA] to Pt Reyes [San Francisco CA] 0–10 nm [11 miles] Small Craft Advisory…Pt Arena [Mendocino CA] to Pigeon Pt [Pescadero CA] 10–60 nm [69 miles] Small Craft Advisory…Pigeon Pt [Pescadero CA] to Pt Piedras Blancas [San Simeon CA] 10–60 nm [69 miles] from 3pm ∨

.MTR WATCHES/WARNINGS/ADVISORIES...
.TDAY...HIGH SURF ADVISORY...CAZ006-505-509-530
SCA...PT ARENA TO PT REYES 0-10 NM
SCA...PT ARENA TO PIGEON PT 10-60 NM
SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM FROM 3 PM [WARN]

Public Forecast: Diaz/Bingaman/Murdock; Aviation: AS; Marine: AS ∨

PUBLIC FORECAST: DIAZ/BINGAMAN/MURDOCK
AVIATION: AS
MARINE: AS [CRED]

VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK]

Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea ∨

FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSBAYAREA
WWW.TWITTER.COM/NWSBAYAREA
WWW.YOUTUBE.COM/NWSBAYAREA [DISC]

Weather NWS glossary About NWS point forecasts Hourly Weather Graph Long-range forecast Radar Satellite Max Temps Graphical Forecast	Area Forecast Discussion FXUS66 KMTR [Monterey CA] 171732 AFDMTR ∨ FXUS66 KMTR 171732 AFDMTR [HEAD] National Weather Service San Francisco Bay Area 9:32am PST Sun Jan 17 2021 ∨ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 932 AM PST SUN JAN 17 2021 [HEAD] Synopsis. Warm, dry weather continues as high pressure lingers over the Pacific Ocean to our west. Two back to back low pressure systems to our east will produce breezy to gusty offshore flow tonight through Tuesday evening. Cooling trend is forecast from Wednesday through Friday. ∨ .SYNOPSIS...WARM, DRY WEATHER CONTINUES AS HIGH PRESSURE LINGERS OVER THE PACIFIC OCEAN TO OUR WEST. TWO BACK TO BACK LOW PRESSURE SYSTEMS TO OUR EAST WILL PRODUCE BREEZY TO GUSTY OFFSHORE FLOW TONIGHT THROUGH TUESDAY EVENING. COOLING TREND IS FORECAST FROM WEDNESDAY THROUGH FRIDAY. [DISC] Discussion. As of 08:36am PST Sunday… a warm start to the day this morning across much of central California and have observed a slight marine layer signature this morning along our immediate coast (akin to what we would normally observe during the summer)as well. Have observed temps across the Bay Area and immediate Central Coast currently ranging between 45–55°F and temps while temps at elevated interior are running a few degrees warmer (~55–65°F)as a result. Upper-level ridge is also set in place through the afternoon, so are looking at another warm day today across the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map], with widespread Max temps in the upper 60s to low 70s F. Please refer to the climate section for today's list of record highs. Switching gears over to our winds, observed breezy conditions along the foothills overnight, with the Oakland Hills north observation at one point measuring sustained NNE winds of 20 mph and a gust of 30 mph. Values were much more pronounced at some of our highest peaks, with Mt Diablo and MT.St Helena reporting gusts over 65 mph between 2 and 3am this morning. The morning Fort Ord and bodega profilers are both picking up on the offshore, NNE winds aloft.these offshore NE winds will become more apparent later this afternoon and evening as these winds from aloft mix down to lower elevations. Be mindful and prepare in advance for windy conditions across the region beginning this evening. ∨ .DISCUSSION...AS OF 08:36 AM PST SUNDAY...A WARM START TO THE DAY THIS MORNING ACROSS MUCH OF CENTRAL CALIFORNIA AND HAVE OBSERVED A SLIGHT MARINE LAYER SIGNATURE THIS MORNING ALONG OUR IMMEDIATE COAST(AKIN TO WHAT WE WOULD NORMALLY OBSERVE DURING THE SUMMER)AS WELL. HAVE OBSERVED TEMPS ACROSS THE BAY AREA AND IMMEDIATE CENTRAL COAST CURRENTLY RANGING BETWEEN 45-55 F AND TEMPS WHILE TEMPS AT ELEVATED INTERIOR ARE RUNNING A FEW DEGREES WARMER (~55-65F)AS A RESULT. UPPER-LEVEL RIDGE IS ALSO SET IN PLACE THROUGH THE AFTERNOON, SO ARE LOOKING AT ANOTHER WARM DAY TODAY ACROSS THE CWA, WITH WIDESPREAD MAX TEMPS IN THE UPPER 60S TO LOW 70S F. PLEASE REFER TO THE CLIMATE SECTION FOR TODAY`S LIST OF RECORD HIGHS. SWITCHING GEARS OVER TO OUR WINDS, OBSERVED BREEZY CONDITIONS ALONG THE FOOTHILLS OVERNIGHT, WITH THE OAKLAND HILLS NORTH OB AT ONE POINT MEASURING SUSTAINED NNE WINDS OF 20MPH AND A GUST OF 30MPH. VALUES WERE MUCH MORE PRONOUNCED AT SOME OF OUR HIGHEST PEAKS, WITH MT. DIABLO AND MT.ST. HELENA REPORTING GUSTS OVER 65MPH BETWEEN 2 AND 3AM THIS MORNING. THE MORNING FT. ORD AND BODEGA PROFILERS ARE BOTH PICKING UP ON THE OFFSHORE, NNE WINDS ALOFT.THESE OFFSHORE NE WINDS WILL BECOME MORE APPARENT LATER THIS AFTERNOON AND EVENING AS THESE WINDS FROM ALOFT MIX DOWN TO LOWER ELEVATIONS. BE MINDFUL AND PREPARE IN ADVANCE FOR WINDY CONDITIONS ACROSS THE REGION BEGINNING THIS EVENING. [DISC] Previous discussion… as of 03:30am PST Sunday. One more day of fairly calm, sunny, and warm weather before our strong offshore wind event impacts the region late tonight into Tuesday. Daytime highs will range from the mid 60s to the upper 70s this afternoon and we may be near or break a few more records. The sites where our current forecast is close to the record include: Santa Rosa, Kentfield, Napa, Livermore, and SFO [San Francisco CA]. ∨ .PREV DISCUSSION...AS OF 03:30 AM PST SUNDAY...ONE MORE DAY OF FAIRLY CALM, SUNNY, AND WARM WEATHER BEFORE OUR STRONG OFFSHORE WIND EVENT IMPACTS THE REGION LATE TONIGHT INTO TUESDAY. DAYTIME HIGHS WILL RANGE FROM THE MID 60S TO THE UPPER 70S THIS AFTERNOON AND WE MAY BE NEAR OR BREAK A FEW MORE RECORDS. THE SITES WHERE OUR CURRENT FORECAST IS CLOSE TO THE RECORD INCLUDE: SANTA ROSA, KENTFIELD, NAPA, LIVERMORE, AND SFO. [DISC] The offshore wind event continues to look strong so use today as an opportunity to prepare. In case of power outages: make sure cell phones/devices are fully charged, gather up flashlights and extra batteries, and have a supply of non-perishable food/water. If there are widespread power outages, remember that it may take crews longer to get the power back on so make sure you have what you need in case you have to go a day or two without power. Other things to remember: secure loose outdoor objects, trim dead tree branches on your property, be cautious when driving as occasionally strong gusts may suddenly hit your vehicle. ∨ THE OFFSHORE WIND EVENT CONTINUES TO LOOK STRONG SO USE TODAY AS AN OPPORTUNITY TO PREPARE. IN CASE OF POWER OUTAGES: MAKE SURE CELL PHONES/DEVICES ARE FULLY CHARGED, GATHER UP FLASHLIGHTS AND EXTRA BATTERIES, AND HAVE A SUPPLY OF NON-PERISHABLE FOOD/WATER. IF THERE ARE WIDESPREAD POWER OUTAGES, REMEMBER THAT IT MAY TAKE CREWS LONGER TO GET THE POWER BACK ON SO MAKE SURE YOU HAVE WHAT YOU NEED IN CASE YOU HAVE TO GO A DAY OR TWO WITHOUT POWER. OTHER THINGS TO REMEMBER: SECURE LOOSE OUTDOOR OBJECTS, TRIM DEAD TREE BRANCHES ON YOUR PROPERTY, BE CAUTIOUS WHEN DRIVING AS OCCASIONALLY STRONG GUSTS MAY SUDDENLY HIT YOUR VEHICLE. [DISC] This offshore event is still set up to arrive in two waves as two lows slide southward to our east. The first one arrives late tonight starting over the North and East Bay hills then downsloping into portions of the valley and spreading across SF Bay Area early Monday morning into Monday afternoon. In fact, we're already seeing hints of the offshore pressure gradient setting up. One of our higher exposed peaks is Mt Diablo and it is already experiencing the increased upper level winds due to its elevation. It has had gusts over 50 mph with a few Max gusts around 70 since midnight. Those enhanced winds will gradually mix down impacting the rest of the North and East Bay terrain tonight. The SFO [San Francisco CA]-Winnemucca [NW Nevada] pressure gradient is a good indication of the intensity of these offshore events and GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] shows a –10 to –13 mb difference for this first wave which is a solid event given that we start paying attention at a –7 mb difference. ∨ THIS OFFSHORE EVENT IS STILL SET UP TO ARRIVE IN TWO WAVES AS TWO LOWS SLIDE SOUTHWARD TO OUR EAST. THE FIRST ONE ARRIVES LATE TONIGHT STARTING OVER THE NORTH AND EAST BAY HILLS THEN DOWNSLOPING INTO PORTIONS OF THE VALLEY AND SPREADING ACROSS SF BAY AREA EARLY MONDAY MORNING INTO MONDAY AFTERNOON. IN FACT, WE`RE ALREADY SEEING HINTS OF THE OFFSHORE PRESSURE GRADIENT SETTING UP. ONE OF OUR HIGHER EXPOSED PEAKS IS MT DIABLO AND IT IS ALREADY EXPERIENCING THE INCREASED UPPER LEVEL WINDS DUE TO ITS ELEVATION. IT HAS HAD GUSTS OVER 50 MPH WITH A FEW MAX GUSTS AROUND 70 SINCE MIDNIGHT. THOSE ENHANCED WINDS WILL GRADUALLY MIX DOWN IMPACTING THE REST OF THE NORTH AND EAST BAY TERRAIN TONIGHT. THE SFO-WMC PRESSURE GRADIENT IS A GOOD INDICATION OF THE INTENSITY OF THESE OFFSHORE EVENTS AND GFS SHOWS A -10 TO -13 MB DIFFERENCE FOR THIS FIRST WAVE WHICH IS A SOLID EVENT GIVEN THAT WE START PAYING ATTENTION AT A -7 MB DIFFERENCE. [DISC] The second and stronger wave arrives Monday night into Tuesday with winds peaking 10pm Monday to 10am Tuesday. For comparison, the GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] has the SFO [San Francisco CA]-Winnemucca [NW Nevada] pressure gradient ranging from –13 to –19 mb. This second wave also impacts the majority of our CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map] as gusty conditions spread southward down to Monterey and San Benito Counties. It's plausible that this second wave might be upgraded to a High Wind Warning if high-resolution models remain consistent with stronger gusts and enhance fire weather concerns. Keeping the summary of this event below as it covers the wind speeds and discusses fire weather concerns: ∨ THE SECOND AND STRONGER WAVE ARRIVES MONDAY NIGHT INTO TUESDAY WITH WINDS PEAKING 10 PM MON TO 10 AM TUES. FOR COMPARISON, THE GFS HAS THE SFO-WMC PRESSURE GRADIENT RANGING FROM -13 TO -19 MB. THIS SECOND WAVE ALSO IMPACTS THE MAJORITY OF OUR CWA AS GUSTY CONDITIONS SPREAD SOUTHWARD DOWN TO MONTEREY AND SAN BENITO COUNTIES. IT`S PLAUSIBLE THAT THIS SECOND WAVE MIGHT BE UPGRADED TO A HIGH WIND WARNING IF HI-RES MODELS REMAIN CONSISTENT WITH STRONGER GUSTS AND ENHANCE FIRE WEATHER CONCERNS. KEEPING THE SUMMARY OF THIS EVENT BELOW AS IT COVERS THE WIND SPEEDS AND DISCUSSES FIRE WEATHER CONCERNS: [DISC] Two pieces to cover. 1) the wind itself. Sustained winds are forecast to be in the 5–20 mph range though populated areas, with the exact value being location dependent. Sustained winds in the hills and mountains are forecast to be in the 15–30 mph range. However, in events like this, it's the gusts that really do the damage. Occasional gusts in valley populated locations could be in the 20–45 mph range, again depending upon location. While in the hills and mountains, expect to see maximum gusts reach 45–60 mph range with the possibility of an isolated site or two trying to jump into the 70+ arena. Branches are dry and brittle in many areas which means they are prone to break and fall, while trees may simply topple in some of the stronger gusts. Please know your risk. Wind statistically is the second leading cause of death due in our area due to falling trees. 2) while we have seen a little rain this winter, it hasn't been a lot and most areas are running about 30% of average on the water year thus far. The rain has helped the larger trees (fuels) to get some moisture in them. However, the fine fuels such as grasses and bushes moisten up quickly and dry out quickly. With the dry warm weather the last few days, it has dried the finer fuels. We have dry grasses, gusty winds coming, and plummeting relative humidities. Since the larger fuels still have moisture, we are not thinking of a Red Flag Warning at this point, but will be watching closely each shift to analyze incoming data. In short, fire concerns exist. Be fire smart, don't be that spark. ∨ TWO PIECES TO COVER. 1) THE WIND ITSELF. SUSTAINED WINDS ARE FORECAST TO BE IN THE 5 TO 20 MPH RANGE THOUGH POPULATED AREAS, WITH THE EXACT VALUE BEING LOCATION DEPENDENT. SUSTAINED WINDS IN THE HILLS AND MOUNTAINS ARE FORECAST TO BE IN THE 15 TO 30 MPH RANGE. HOWEVER, IN EVENTS LIKE THIS, IT`S THE GUSTS THAT REALLY DO THE DAMAGE. OCCASIONAL GUSTS IN VALLEY POPULATED LOCATIONS COULD BE IN THE 20 TO 45 MPH RANGE, AGAIN DEPENDING UPON LOCATION. WHILE IN THE HILLS AND MOUNTAINS, EXPECT TO SEE MAXIMUM GUSTS REACH 45 TO 60 MPH RANGE WITH THE POSSIBILITY OF AN ISOLATED SITE OR TWO TRYING TO JUMP INTO THE 70+ ARENA. BRANCHES ARE DRY AND BRITTLE IN MANY AREAS WHICH MEANS THEY ARE PRONE TO BREAK AND FALL, WHILE TREES MAY SIMPLY TOPPLE IN SOME OF THE STRONGER GUSTS. PLEASE KNOW YOUR RISK. WIND STATISTICALLY IS THE SECOND LEADING CAUSE OF DEATH DUE IN OUR AREA DUE TO FALLING TREES. 2) WHILE WE HAVE SEEN A LITTLE RAIN THIS WINTER, IT HASN`T BEEN A LOT AND MOST AREAS ARE RUNNING ABOUT 30% OF AVERAGE ON THE WATER YEAR THUS FAR. THE RAIN HAS HELPED THE LARGER TREES (FUELS) TO GET SOME MOISTURE IN THEM. HOWEVER, THE FINE FUELS SUCH AS GRASSES AND BUSHES MOISTEN UP QUICKLY AND DRY OUT QUICKLY. WITH THE DRY WARM WEATHER THE LAST FEW DAYS, IT HAS DRIED THE FINER FUELS. WE HAVE DRY GRASSES, GUSTY WINDS COMING, AND PLUMMETING RELATIVE HUMIDITIES. SINCE THE LARGER FUELS STILL HAVE MOISTURE, WE ARE NOT THINKING OF A RED FLAG WARNING AT THIS POINT, BUT WILL BE WATCHING CLOSELY EACH SHIFT TO ANALYZE INCOMING DATA. IN SHORT, FIRE CONCERNS EXIST. BE FIRE SMART, DON`T BE THAT SPARK. [DISC] Breezy offshore conditions could linger into Wednesday morning but taper off in the afternoon. Highs for Wednesday are forecast to remain well above average with most areas seeing highs in the upper 60s. Wednesday looks to continue the trend of dry and clear skies, but that will likely change the following day. ∨ BREEZY OFFSHORE CONDITIONS COULD LINGER INTO WEDNESDAY MORNING BUT TAPER OFF IN THE AFTERNOON. HIGHS FOR WEDNESDAY ARE FORECAST TO REMAIN WELL ABOVE AVERAGE WITH MOST AREAS SEEING HIGHS IN THE UPPER 60S. WEDNESDAY LOOKS TO CONTINUE THE TREND OF DRY AND CLEAR SKIES, BUT THAT WILL LIKELY CHANGE THE FOLLOWING DAY. [DISC] Thursday offers quite a change to the pattern as winds shift to an onshore flow as low pressure moves into Northern California. This will initiate a cooling trend to start on Thursday with highs still slightly above average, just more focused around the 60° mark. The GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] and ECMWF [European Center for Medium-Range Weather Forecasts model] agree on the onshore flow, but disagree on moisture and how westerly the winds will get. The GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] is optimistic for rain chances and more westerly winds, while the national blend and the ECMWF [European Center for Medium-Range Weather Forecasts model] are only offering slight chances and winds from the northwest. Models and ensembles are placing their initial rain chances into Thursday night, but the GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] wants these chances to last much longer. The GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] continues the chances for light rain into the weekend, but not many other forecasts are being so bold. Regardless, what rain does fall during this time looks to only fall at mild rates. ∨ THURSDAY OFFERS QUITE A CHANGE TO THE PATTERN AS WINDS SHIFT TO AN ONSHORE FLOW AS LOW PRESSURE MOVES INTO NORTHERN CALIFORNIA. THIS WILL INITIATE A COOLING TREND TO START ON THURSDAY WITH HIGHS STILL SLIGHTLY ABOVE AVERAGE, JUST MORE FOCUSED AROUND THE 60 DEGREE MARK. THE GFS AND ECMWF AGREE ON THE ONSHORE FLOW, BUT DISAGREE ON MOISTURE AND HOW WESTERLY THE WINDS WILL GET. THE GFS IS OPTIMISTIC FOR RAIN CHANCES AND MORE WESTERLY WINDS, WHILE THE NATIONAL BLEND AND THE ECMWF ARE ONLY OFFERING SLIGHT CHANCES AND WINDS FROM THE NORTHWEST. MODELS AND ENSEMBLES ARE PLACING THEIR INITIAL RAIN CHANCES INTO THURSDAY NIGHT, BUT THE GFS WANTS THESE CHANCES TO LAST MUCH LONGER. THE GFS CONTINUES THE CHANCES FOR LIGHT RAIN INTO THE WEEKEND, BUT NOT MANY OTHER FORECASTS ARE BEING SO BOLD. REGARDLESS, WHAT RAIN DOES FALL DURING THIS TIME LOOKS TO ONLY FALL AT MILD RATES. [DISC] Despite the rain disagreement, models show the cooling trend continuing into the weekend. Near average highs are expected for the tail end of the forecast. Some areas could start seeing below average overnight lows. A few interior areas could even see freezing temperatures to start Saturday and Sunday, but this could be limited by how much moisture is in the region. ∨ DESPITE THE RAIN DISAGREEMENT, MODELS SHOW THE COOLING TREND CONTINUING INTO THE WEEKEND. NEAR AVERAGE HIGHS ARE EXPECTED FOR THE TAIL END OF THE FORECAST. SOME AREAS COULD START SEEING BELOW AVERAGE OVERNIGHT LOWS. A FEW INTERIOR AREAS COULD EVEN SEE FREEZING TEMPERATURES TO START SATURDAY AND SUNDAY, BUT THIS COULD BE LIMITED BY HOW MUCH MOISTURE IS IN THE REGION. [DISC] Aviation. As of 09:32am PST Sunday… for the 18Z [10am PST] TAFs [Terminal Aerodrome Forecasts]. Widespread VFR [Visual Flight Rules] conditions as breezy offshore winds persist across the higher elevations. VFR [Visual Flight Rules] conditions to prevail through the period with patchy fog possible late this evening around KMRY [Monterey CA] and KSNS [Salinas CA]. Offshore winds aloft will diminish into this afternoon before increasing again late tonight. Low-level wind shear will become an issue starting late tonight with winds at 1500–2000 ft at around 30–35 kt [35–40 mph] near many of the North Bay and Bay Area terminals. Gusts will start to mix down to the surface towards the end of the TAF [Terminal Aerodrome Forecast] period. An additional round of stronger and more widespread offshore winds is expected tomorrow night with strong surface gusts also anticipated. ∨ .AVIATION...AS OF 09:32 AM PST SUNDAY...FOR THE 18Z TAFS. WIDESPREAD VFR CONDITIONS AS BREEZY OFFSHORE WINDS PERSIST ACROSS THE HIGHER ELEVATIONS. VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD WITH PATCHY FOG POSSIBLE LATE THIS EVENING AROUND KMRY AND KSNS. OFFSHORE WINDS ALOFT WILL DIMINISH INTO THIS AFTERNOON BEFORE INCREASING AGAIN LATE TONIGHT. LLWS WILL BECOME AN ISSUE STARTING LATE TONIGHT WITH WINDS AT 1500 TO 2000 FT AT AROUND 30 TO 35 KT NEAR MANY OF THE NORTH BAY AND BAY AREA TERMINALS. GUSTS WILL START TO MIX DOWN TO THE SURFACE TOWARDS THE END OF THE TAF PERIOD. AN ADDITIONAL ROUND OF STRONGER AND MORE WIDESPREAD OFFSHORE WINDS IS EXPECTED TOMORROW NIGHT WITH STRONG SURFACE GUSTS ALSO ANTICIPATED. [AVIA] Vicinity of KSFO [San Francisco CA]… VFR [Visual Flight Rules] with some passing high clouds. Light winds this morning with diminishing low-level wind shear into this afternoon. Onshore winds this afternoon around 10–15 kt [12–17 mph]. Increasing offshore winds aloft tonight will generate low-level wind shear concerns through the rest of the TAF [Terminal Aerodrome Forecast] period. Stronger offshore winds expected tomorrow night. ∨ VICINITY OF KSFO...VFR WITH SOME PASSING HIGH CLOUDS. LIGHT WINDS THIS MORNING WITH DIMINISHING LLWS INTO THIS AFTERNOON. ONSHORE WINDS THIS AFTERNOON AROUND 10 TO 15 KT. INCREASING OFFSHORE WINDS ALOFT TONIGHT WILL GENERATE LLWS CONCERNS THROUGH THE REST OF THE TAF PERIOD. STRONGER OFFSHORE WINDS EXPECTED TOMORROW NIGHT. [AVI2] SFO [San Francisco CA] bridge approach… similar to KSFO [San Francisco CA]. ∨ SFO BRIDGE APPROACH...SIMILAR TO KSFO. [AVI2] Monterey Bay terminals… VFR [Visual Flight Rules]. Light winds this morning turning NW this afternoon. May see some patchy fog again late this evening but should mix out overnight. ∨ MONTEREY BAY TERMINALS...VFR. LIGHT WINDS THIS MORNING TURNING NW THIS AFTERNOON. MAY SEE SOME PATCHY FOG AGAIN LATE THIS EVENING BUT SHOULD MIX OUT OVERNIGHT. [AVI2] Beaches… as of 04:05am PST Sunday… a large, very long period northwest swell will arrive this morning and result in hazardous conditions along the coast today through Monday afternoon. Forerunners are expected to arrive at 3–7 feet with a period of 22–24 seconds through this morning, increasing the risk of sneaker waves. Swell heights are then expected to build later Sunday into Monday with breaking waves of 18–22 feet, locally higher at favored breakpoints, expected along west to northwest facing beaches. As a result, a High Surf Advisory is in effect through Monday afternoon for west and northwest facing beaches while a beach hazard statement has been issued for the northern Monterey Bay including Santa Cruz. With unseasonably warm temperatures this holiday weekend, it will likely attract more people to the coast. Individuals should be reminded that our coastline and the cold Pacific waters remain dangerous as these larger than normal waves impact the coast. Extreme caution is advised when visiting area beaches. Never turn your back to the ocean. ∨ .BEACHES...AS OF 04:05 AM PST SUNDAY...A LARGE, VERY LONG PERIOD NORTHWEST SWELL WILL ARRIVE THIS MORNING AND RESULT IN HAZARDOUS CONDITIONS ALONG THE COAST TODAY THROUGH MONDAY AFTERNOON. FORERUNNERS ARE EXPECTED TO ARRIVE AT 3 TO 7 FEET WITH A PERIOD OF 22 TO 24 SECONDS THROUGH THIS MORNING, INCREASING THE RISK OF SNEAKER WAVES. SWELL HEIGHTS ARE THEN EXPECTED TO BUILD LATER SUNDAY INTO MONDAY WITH BREAKING WAVES OF 18 TO 22 FEET, LOCALLY HIGHER AT FAVORED BREAKPOINTS, EXPECTED ALONG WEST TO NORTHWEST FACING BEACHES. AS A RESULT, A HIGH SURF ADVISORY IS IN EFFECT THROUGH MONDAY AFTERNOON FOR WEST AND NORTHWEST FACING BEACHES WHILE A BEACH HAZARD STATEMENT HAS BEEN ISSUED FOR THE NORTHERN MONTEREY BAY INCLUDING SANTA CRUZ. WITH UNSEASONABLY WARM TEMPERATURES THIS HOLIDAY WEEKEND, IT WILL LIKELY ATTRACT MORE PEOPLE TO THE COAST. INDIVIDUALS SHOULD BE REMINDED THAT OUR COASTLINE AND THE COLD PACIFIC WATERS REMAIN DANGEROUS AS THESE LARGER THAN NORMAL WAVES IMPACT THE COAST. EXTREME CAUTION IS ADVISED WHEN VISITING AREA BEACHES. NEVER TURN YOUR BACK TO THE OCEAN. [DISC] Climate. Record type: highs (old record temp/year) ∨ .CLIMATE...RECORD TYPE: HIGHS (OLD RECORD TEMP/YEAR) [AVIA] Jan 17th Jan 18th ∨ JAN 17TH JAN 18TH [POPS] Santa Rosa 71/1991 74/1976 Kentfield 71/1994 70/2014 Napa 72/1920 76/1920 Richmond 73/2009 71/2018 Livermore 70/1986 74/1919 San Francisco 73/1991 70/1920 SFO 70/1991 68/1948 Redwood City 77/1948 74/2009 Half Moon Bay 75/2009 72/2009 Oakland downtown 74/2014 73/2014 San Jose 76/1920 74/1920 Gilroy 77/2014 80/2014* Santa Cruz 83/2014 83/1920 Salinas Airport 86/2014* 81/1994 King City 86/2014* 83/2009 ∨ SANTA ROSA 71/1991 74/1976 KENTFIELD 71/1994 70/2014 NAPA 72/1920 76/1920 RICHMOND 73/2009 71/2018 LIVERMORE 70/1986 74/1919 SAN FRANCISCO 73/1991 70/1920 SFO 70/1991 68/1948 REDWOOD CITY 77/1948 74/2009 HALF MOON BAY 75/2009 72/2009 OAKLAND DOWNTOWN 74/2014 73/2014 SAN JOSE 76/1920 74/1920 GILROY 77/2014 80/2014* SANTA CRUZ 83/2014 83/1920 SALINAS AIRPORT 86/2014* 81/1994 KING CITY 86/2014* 83/2009 [POPS] monthly records ∨ MONTHLY RECORDS [DISC] Marine. As of 08:22am PST Sunday… moderate to locally strong north to northwest winds will prevail over the waters today. The strongest winds are expected over the northern outer waters where occasional low end gale-force gusts will be possible. Locally breezy conditions will also be present along the Big Sur coast south of Point Sur [Big Sur CA]. These winds will persist into tomorrow before a burst of offshore winds over land spills over into the waters starting tomorrow night. This will bring gale force conditions across the nearshore waters and through portions of the San Francisco Bay into mid-week. A large, very long period northwest swell will arrive today and persist through late tomorrow bringing additional hazards for small crafts. ∨ .MARINE...AS OF 08:22 AM PST SUNDAY...MODERATE TO LOCALLY STRONG NORTH TO NORTHWEST WINDS WILL PREVAIL OVER THE WATERS TODAY. THE STRONGEST WINDS ARE EXPECTED OVER THE NORTHERN OUTER WATERS WHERE OCCASIONAL LOW END GALE-FORCE GUSTS WILL BE POSSIBLE. LOCALLY BREEZY CONDITIONS WILL ALSO BE PRESENT ALONG THE BIG SUR COAST SOUTH OF POINT SUR. THESE WINDS WILL PERSIST INTO TOMORROW BEFORE A BURST OF OFFSHORE WINDS OVER LAND SPILLS OVER INTO THE WATERS STARTING TOMORROW NIGHT. THIS WILL BRING GALE FORCE CONDITIONS ACROSS THE NEARSHORE WATERS AND THROUGH PORTIONS OF THE SAN FRANCISCO BAY INTO MID-WEEK. A LARGE, VERY LONG PERIOD NORTHWEST SWELL WILL ARRIVE TODAY AND PERSIST THROUGH LATE TOMORROW BRINGING ADDITIONAL HAZARDS FOR SMALL CRAFTS. [AVIA] MTR Watches/Warnings/Advisories Today: High Surf Advisory…CAZ006–505–509–530 Small Craft Advisory…Pt Arena [Mendocino CA] to Pt Reyes [San Francisco CA] 0–10 nm [11 miles] Small Craft Advisory…Pt Arena [Mendocino CA] to Pigeon Pt [Pescadero CA] 10–60 nm [69 miles] Small Craft Advisory…Pigeon Pt [Pescadero CA] to Pt Piedras Blancas [San Simeon CA] 10–60 nm [69 miles] from 3pm ∨ .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...HIGH SURF ADVISORY...CAZ006-505-509-530 SCA...PT ARENA TO PT REYES 0-10 NM SCA...PT ARENA TO PIGEON PT 10-60 NM SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM FROM 3 PM [WARN] Public Forecast: Diaz/Bingaman/Murdock; Aviation: AS; Marine: AS ∨ PUBLIC FORECAST: DIAZ/BINGAMAN/MURDOCK AVIATION: AS MARINE: AS [CRED] VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK] Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea ∨ FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA [DISC]	Point Forecast Half Moon Bay Airport 17 Jan 12:55pm PST This Afternoon Sunny, with a high near 65°. NNW wind around 9 mph. Tonight Partly cloudy, with a low around 46°. NNW wind 3 to 6 mph. M.L.King Day Sunny, with a high near 69°. NNE wind 11 to 16 mph, with gusts as high as 31 mph. Monday Night Mostly clear, with a low around 48°. Windy, with a NNE wind 31 to 38 mph, with gusts as high as 60 mph. Tuesday Sunny, with a high near 67°. Breezy, with a NNE wind 22 to 28 mph, with gusts as high as 46 mph. Tuesday Night Mostly clear, with a low around 43°. Breezy. Wednesday Sunny, with a high near 62°. Wednesday Night Mostly clear, with a low around 41°. Thursday Mostly sunny, with a high near 56°. Thursday Night Partly cloudy, with a low around 43°. Friday A slight chance of rain. Mostly sunny, with a high near 54°. Friday Night Mostly clear, with a low around 40°. Saturday Sunny, with a high near 55°. This Afternoon Sunny, with a high near 65. North northwest wind around 9 mph. Tonight Partly cloudy, with a low around 46. North northwest wind 3 to 6 mph. M.L.King Day Sunny, with a high near 69. North northeast wind 11 to 16 mph, with gusts as high as 31 mph. Monday Night Mostly clear, with a low around 48. Windy, with a north northeast wind 31 to 38 mph, with gusts as high as 60 mph. Tuesday Sunny, with a high near 67. Breezy, with a north northeast wind 22 to 28 mph, with gusts as high as 46 mph. Tuesday Night Mostly clear, with a low around 43. Breezy. Wednesday Sunny, with a high near 62. Wednesday Night Mostly clear, with a low around 41. Thursday Mostly sunny, with a high near 56. Thursday Night Partly cloudy, with a low around 43. Friday A slight chance of rain. Mostly sunny, with a high near 54. Friday Night Mostly clear, with a low around 40. Saturday Sunny, with a high near 55.
This page is generated dynamically from the National Weather Service's NWS point forecast and Area Forecast Discussion, reformatted for readability. NWS glossary; about point forecasts. For more information, visit the Lobitos Weather Project home page. Comments and corrections are welcome: