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FXUS66 KMTR [Monterey CA] 220535 AFDMTR 

FXUS66 KMTR 220535
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 10:35pm PDT Sat Sep 21 2019 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1035 PM PDT SAT SEP 21 2019 [HEAD]

Synopsis. Most areas will experience some cooling tomorrow and Monday as an upper low slides down inland California and into the desert southwest. High pressure will then build over the eastern Pacific early to mid next week. This combination will bring continued warming temperatures, dry offshore flow and increased fire weather concerns. A trough of low pressure will move through the region late next week resulting in significantly cooler temperatures and possible precipitation. 

.SYNOPSIS...MOST AREAS WILL EXPERIENCE SOME COOLING TOMORROW AND
MONDAY AS AN UPPER LOW SLIDES DOWN INLAND CALIFORNIA AND INTO THE
DESERT SOUTHWEST. HIGH PRESSURE WILL THEN BUILD OVER THE EASTERN
PACIFIC EARLY TO MID NEXT WEEK. THIS COMBINATION WILL BRING
CONTINUED WARMING TEMPERATURES, DRY OFFSHORE FLOW AND INCREASED
FIRE WEATHER CONCERNS. A TROUGH OF LOW PRESSURE WILL MOVE THROUGH
THE REGION LATE NEXT WEEK RESULTING IN SIGNIFICANTLY COOLER
TEMPERATURES AND POSSIBLE PRECIPITATION. [DISC]

Discussion. As of 9:10pm PST Saturday… clear skies along with an upper level ridge moving through the West Coast today brought 3–5° of warming across the district today. Highs today were about 8–10° above normal. No sign of stratus on this evening's satellite image as the pressure gradients indicate a dry north-south flow. Patchy low clouds could form late tonight near the coast and over the coastal hills but most areas will see another clear night. The only update was to reduce the amount of clouds and fog for tonight. 

.DISCUSSION...AS OF 9:10 PM PST SATURDAY...CLEAR SKIES ALONG WITH
AN UPPER LEVEL RIDGE MOVING THROUGH THE WEST COAST TODAY BROUGHT
3 TO 5 DEGREES OF WARMING ACROSS THE DISTRICT TODAY. HIGHS TODAY
WERE ABOUT 8 TO 10 DEGREES ABOVE NORMAL. NO SIGN OF STRATUS ON
THIS EVENINGS SATELLITE IMAGE AS THE PRESSURE GRADIENTS INDICATE A
DRY NORTH-SOUTH FLOW. PATCHY LOW CLOUDS COULD FORM LATE TONIGHT
NEAR THE COAST AND OVER THE COASTAL HILLS BUT MOST AREAS WILL SEE
ANOTHER CLEAR NIGHT. THE ONLY UPDATE WAS TO REDUCE THE AMOUNT OF
CLOUDS AND FOG FOR TONIGHT. [DISC]

Previous discussion… as of 02:28pm PDT Saturday. Temperatures across the region this afternoon are around 5° warmer than yesterday as an upper ridge is stretched over California and northward into the Pacific Northwest. Most locations are currently in the upper 70s to mid 80s with isolated areas in the low 90s. Expect a few degrees of additional warming today with temperatures peaking in the low 70s to low 80s along the coast to mid 80s and 90s inland. The upper ridge will quickly shift eastward into tomorrow and be replaced by an upper trough. The upper trough will split into a cut off low on Monday that will move southward across interior California and Nevada before settling into the desert southwest Monday night. This will stall warming across the area and bring some minor cooling to some locations for tomorrow and Monday. 

PREVIOUS DISCUSSION...AS OF 02:28 PM PDT SATURDAY...TEMPERATURES
ACROSS THE REGION THIS AFTERNOON ARE AROUND 5 DEGREES WARMER THAN
YESTERDAY AS AN UPPER RIDGE IS STRETCHED OVER CALIFORNIA AND
NORTHWARD INTO THE PACIFIC NORTHWEST. MOST LOCATIONS ARE CURRENTLY
IN THE UPPER 70S TO MID 80S WITH ISOLATED AREAS IN THE LOW 90S.
EXPECT A FEW DEGREES OF ADDITIONAL WARMING TODAY WITH TEMPERATURES
PEAKING IN THE LOW 70S TO LOW 80S ALONG THE COAST TO MID 80S AND
90S INLAND. THE UPPER RIDGE WILL QUICKLY SHIFT EASTWARD INTO
TOMORROW AND BE REPLACED BY AN UPPER TROUGH. THE UPPER TROUGH WILL
SPLIT INTO A CUT OFF LOW ON MONDAY THAT WILL MOVE SOUTHWARD
ACROSS INTERIOR CALIFORNIA AND NEVADA BEFORE SETTLING INTO THE
DESERT SOUTHWEST MONDAY NIGHT. THIS WILL STALL WARMING ACROSS THE
AREA AND BRING SOME MINOR COOLING TO SOME LOCATIONS FOR TOMORROW
AND MONDAY. [DISC]

The combination of low pressure to our southeast and high pressure over the eastern Pacific will create offshore flow across the region from Monday night into Wednesday morning. This will bring warm to hot temperatures across the region Tuesday and Wednesday with offshore flow bringing these temperatures to coastal areas as well. 850 mb temperatures look similar to the last brief heat event at around 22–23°C. Models did a fairly poor job in the extended of capturing the degree of warming expected, particularly for coastal areas. Given that this event will likely bringing stronger offshore flow, went ahead and bumped up temperatures for Tuesday. For now, expecting coastal areas in the 80s with low 90s possible around the northern Monterey Bay and along the San Francisco Bay shoreline. Interior locations are currently forecast in the 90s to low 100s. Uncertainty remains fairly high as temperatures will depend on the strength of the offshore flow. As we get closer to Tuesday, will look into whether or not heat products are necessary. Wednesday looks to be warm as well but a few degrees cooler as onshore flow returns. The other concern with this pattern will be for fire weather (see discussion below). Dry/gusty offshore winds and low humidities could bring critical fire weather conditions to the North and East Bay hills Monday night through early Wednesday morning. Therefore, a Fire Weather Watch has been issued. 

THE COMBINATION OF LOW PRESSURE TO OUR SOUTHEAST AND HIGH PRESSURE
OVER THE EASTERN PACIFIC WILL CREATE OFFSHORE FLOW ACROSS THE
REGION FROM MONDAY NIGHT INTO WEDNESDAY MORNING. THIS WILL BRING
WARM TO HOT TEMPERATURES ACROSS THE REGION TUESDAY AND WEDNESDAY
WITH OFFSHORE FLOW BRINGING THESE TEMPERATURES TO COASTAL AREAS AS
WELL. 850 MB TEMPERATURES LOOK SIMILAR TO THE LAST BRIEF HEAT
EVENT AT AROUND 22-23 DEG C. MODELS DID A FAIRLY POOR JOB IN THE
EXTENDED OF CAPTURING THE DEGREE OF WARMING EXPECTED, PARTICULARLY
FOR COASTAL AREAS. GIVEN THAT THIS EVENT WILL LIKELY BRINGING
STRONGER OFFSHORE FLOW, WENT AHEAD AND BUMPED UP TEMPERATURES FOR
TUESDAY. FOR NOW, EXPECTING COASTAL AREAS IN THE 80S WITH LOW 90S
POSSIBLE AROUND THE NORTHERN MONTEREY BAY AND ALONG THE SAN
FRANCISCO BAY SHORELINE. INTERIOR LOCATIONS ARE CURRENTLY FORECAST
IN THE 90S TO LOW 100S. UNCERTAINTY REMAINS FAIRLY HIGH AS
TEMPERATURES WILL DEPEND ON THE STRENGTH OF THE OFFSHORE FLOW. AS
WE GET CLOSER TO TUESDAY, WILL LOOK INTO WHETHER OR NOT HEAT
PRODUCTS ARE NECESSARY. WEDNESDAY LOOKS TO BE WARM AS WELL BUT A
FEW DEGREES COOLER AS ONSHORE FLOW RETURNS. THE OTHER CONCERN WITH
THIS PATTERN WILL BE FOR FIRE WEATHER (SEE DISCUSSION BELOW).
DRY/GUSTY OFFSHORE WINDS AND LOW HUMIDITIES COULD BRING CRITICAL
FIRE WEATHER CONDITIONS TO THE NORTH AND EAST BAY HILLS MONDAY
NIGHT THROUGH EARLY WEDNESDAY MORNING. THEREFORE, A FIRE WEATHER
WATCH HAS BEEN ISSUED. [DISC]

Temperatures will then cool down quickly late this week as a deep mid/upper trough forms over the West Coast and then digs into California. This will bring high temperatures down around 10–15° inland from Wednesday to Thursday and leave highs across the region well below normal by Friday. There are still differences between the models as to the positioning and timing of this system at the end of the week, but the Central Coast and Bay Area could see some precipitation into the start of next weekend. Lots of weather changes for the area this week. Stay tuned to the forecast. 

TEMPERATURES WILL THEN COOL DOWN QUICKLY LATE THIS WEEK AS A DEEP
MID/UPPER TROUGH FORMS OVER THE WEST COAST AND THEN DIGS INTO
CALIFORNIA. THIS WILL BRING HIGH TEMPERATURES DOWN AROUND 10 TO 15
DEGREES INLAND FROM WEDNESDAY TO THURSDAY AND LEAVE HIGHS ACROSS
THE REGION WELL BELOW NORMAL BY FRIDAY. THERE ARE STILL DIFFERENCES
BETWEEN THE MODELS AS TO THE POSITIONING AND TIMING OF THIS
SYSTEM AT THE END OF THE WEEK, BUT THE CENTRAL COAST AND BAY AREA
COULD SEE SOME PRECIPITATION INTO THE START OF NEXT WEEKEND. LOTS
OF WEATHER CHANGES FOR THE AREA THIS WEEK. STAY TUNED TO THE
FORECAST. [DISC]

Aviation. As of 10:35pm PDT Saturday… for 06Z [11pm PDT] TAFs [Terminal Aerodrome Forecasts]. Clear skies will prevail across the region through the forecast period. Patchy low clouds may redevelop along the coast however the marine layer will remain compressed limiting any inland intrusion of the low clouds. Therefore all ceilings have been removed from the TAFs [Terminal Aerodrome Forecasts] for Sunday morning. Winds will continue to diminish overnight becoming light and locally variable. 

.AVIATION...AS OF 10:35 PM PDT SATURDAY...FOR 06Z TAFS. CLEAR
SKIES WILL PREVAIL ACROSS THE REGION THROUGH THE FORECAST PERIOD.
PATCHY LOW CLOUDS MAY REDEVELOP ALONG THE COAST HOWEVER THE MARINE
LAYER WILL REMAIN COMPRESSED LIMITING ANY INLAND INTRUSION OF THE
LOW CLOUDS. THEREFORE ALL CIGS HAVE BEEN REMOVED FROM THE TAFS
FOR SUNDAY MORNING. WINDS WILL CONTINUE TO DIMINISH OVERNIGHT
BECOMING LIGHT AND LOCALLY VARIABLE. [AVIA]

Vicinity of KSFO [San Francisco CA]VFR [Visual Flight Rules] conditions will prevail through the forecast period. Breezy winds will continue to diminish becoming light and variable overnight. 

VICINITY OF KSFO...VFR CONDITIONS WILL PREVAIL THROUGH THE
FORECAST PERIOD. BREEZY WINDS WILL CONTINUE TO DIMINISH BECOMING
LIGHT AND VARIABLE OVERNIGHT. [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] conditions will prevail through the forecast period. Light winds. 

MONTEREY BAY TERMINALS...VFR CONDITIONS WILL PREVAIL THROUGH THE
FORECAST PERIOD. LIGHT WINDS. [AVI2]

Fire weather. As of 2:28pm PDT Saturday… as of yesterday, the energy release component (ERC [Energy Release Component]) and 100 hour fuel values are right around normal for the region. An inside slider is still expected to bring an offshore flow event Monday night and through early Wednesday morning. A Fire Weather Watch has been issued from 9pm Monday to 5am Wednesday for the North Bay mountains and East Bay hills & Diablo Range. Offshore flow will develop on Monday with winds peaking Monday night into Tuesday morning. The strongest winds thus far are expected in the North Bay mountains where the local WRF [Weather Research and Forecasting model] model shows gusts up to 45 mph possible overnight Monday. Generally expect north to northeast winds 10–25 mph with gusts 30–35 mph. Winds will ease some Tuesday morning, but will increase and become gusty again in the afternoon and overnight. Daytime humidity values are forecast in the teens to low 20s with poor overnight humidity recoveries both Monday and Tuesday night of 30–50%. Additionally, very warm to hot conditions are forecast for Tuesday with highs in the low to mid 90s and isolated areas reaching triple digits. This along with low humidities will contribute to further drying of fuels. 

.FIRE WEATHER...AS OF 2:28 PM PDT SATURDAY...AS OF YESTERDAY, THE
ENERGY RELEASE COMPONENT (ERC) AND 100 HOUR FUEL VALUES ARE RIGHT
AROUND NORMAL FOR THE REGION. AN INSIDE SLIDER IS STILL EXPECTED
TO BRING AN OFFSHORE FLOW EVENT MONDAY NIGHT AND THROUGH EARLY
WEDNESDAY MORNING. A FIRE WEATHER WATCH HAS BEEN ISSUED FROM 9 PM
MONDAY TO 5 AM WEDNESDAY FOR THE NORTH BAY MOUNTAINS AND EAST BAY
HILLS & DIABLO RANGE. OFFSHORE FLOW WILL DEVELOP ON MONDAY WITH
WINDS PEAKING MONDAY NIGHT INTO TUESDAY MORNING. THE STRONGEST
WINDS THUS FAR ARE EXPECTED IN THE NORTH BAY MOUNTAINS WHERE THE
LOCAL WRF MODEL SHOWS GUSTS UP TO 45 MPH POSSIBLE OVERNIGHT
MONDAY. GENERALLY EXPECT NORTH TO NORTHEAST WINDS 10 TO 25 MPH
WITH GUSTS 30 TO 35 MPH. WINDS WILL EASE SOME TUESDAY MORNING, BUT
WILL INCREASE AND BECOME GUSTY AGAIN IN THE AFTERNOON AND
OVERNIGHT. DAYTIME HUMIDITY VALUES ARE FORECAST IN THE TEENS TO
LOW 20S WITH POOR OVERNIGHT HUMIDITY RECOVERIES BOTH MONDAY AND
TUESDAY NIGHT OF 30 TO 50 PERCENT. ADDITIONALLY, VERY WARM TO HOT
CONDITIONS ARE FORECAST FOR TUESDAY WITH HIGHS IN THE LOW TO MID
90S AND ISOLATED AREAS REACHING TRIPLE DIGITS. THIS ALONG WITH LOW
HUMIDITIES WILL CONTRIBUTE TO FURTHER DRYING OF FUELS. [AVIA]

Marine. As of 8:53pm PDT Saturday… light to locally breezy northwest winds across the waters through this weekend. Strongest winds will in the outer waters north of Point Reyes [San Francisco CA] where hazardous squared seas are also possible. Winds will increase again by Monday as another low pressure trough drops into the Great Basin. A 9–10 second northwest swell will be mixed with a long-period southerly swell. 

.MARINE...AS OF 8:53 PM PDT SATURDAY...LIGHT TO LOCALLY BREEZY
NORTHWEST WINDS ACROSS THE WATERS THROUGH THIS WEEKEND. STRONGEST
WINDS WILL IN THE OUTER WATERS NORTH OF POINT REYES WHERE
HAZARDOUS SQUARED SEAS ARE ALSO POSSIBLE. WINDS WILL INCREASE
AGAIN BY MONDAY AS ANOTHER LOW PRESSURE TROUGH DROPS INTO THE
GREAT BASIN. A 9 TO 10 SECOND NORTHWEST SWELL WILL BE MIXED WITH A
LONG-PERIOD SOUTHERLY SWELL. [AVIA]

MTR Watches/Warnings/Advisories

  • Tonight: Small Craft AdvisoryPt Arena [Mendocino CA] to Pigeon Pt [Pescadero CA] 10–60 nm [69 miles] Small Craft AdvisoryPt Arena [Mendocino CA] to Pt Reyes [San Francisco CA] 0–10 nm [11 miles] from 3am 
.MTR WATCHES/WARNINGS/ADVISORIES...
.TNGT...SCA...PT ARENA TO PIGEON PT 10-60 NM
SCA...PT ARENA TO PT REYES 0-10 NM FROM 3 AM [WARN]

Public Forecast: W PI; Aviation: CW; Marine: Sims/CW 

PUBLIC FORECAST: W PI
AVIATION: CW
MARINE: SIMS/CW [CRED]
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK]

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Point Forecast

Montara CA

22 Sep 12:55am PDT

Overnight Patchy fog. Otherwise, mostly cloudy, with a low around 56°. Light NW wind.
Sunday Patchy fog before 11am. Otherwise, mostly cloudy, with a high near 65°. Calm wind becoming WNW 5 to 9 mph in the afternoon.
Sunday Night Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 56°. WNW wind 9 to 13 mph.
Monday Patchy fog before 8am. Otherwise, mostly sunny, with a high near 67°. Light NNW wind increasing to 6 to 11 mph in the afternoon.
Monday Night Mostly clear, with a low around 57°. North wind 5 to 9 mph.
Tuesday Sunny, with a high near 72°.
Tuesday Night Mostly clear, with a low around 57°.
Wednesday Sunny, with a high near 71°.
Wednesday Night Mostly clear, with a low around 57°.
Thursday Sunny, with a high near 64°.
Thursday Night Partly cloudy, with a low around 55°.
Friday A slight chance of showers. Mostly sunny, with a high near 62°.
Friday Night A chance of showers. Mostly cloudy, with a low around 54°.
Saturday A chance of showers. Mostly sunny, with a high near 64°.
Overnight
Patchy fog. Otherwise, mostly cloudy, with a low around 56. Light northwest wind.
Sunday
Patchy fog before 11am. Otherwise, mostly cloudy, with a high near 65. Calm wind becoming west northwest 5 to 9 mph in the afternoon.
Sunday Night
Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 56. West northwest wind 9 to 13 mph.
Monday
Patchy fog before 8am. Otherwise, mostly sunny, with a high near 67. Light north northwest wind increasing to 6 to 11 mph in the afternoon.
Monday Night
Mostly clear, with a low around 57. North wind 5 to 9 mph.
Tuesday
Sunny, with a high near 72.
Tuesday Night
Mostly clear, with a low around 57.
Wednesday
Sunny, with a high near 71.
Wednesday Night
Mostly clear, with a low around 57.
Thursday
Sunny, with a high near 64.
Thursday Night
Partly cloudy, with a low around 55.
Friday
A slight chance of showers. Mostly sunny, with a high near 62.
Friday Night
A chance of showers. Mostly cloudy, with a low around 54.
Saturday
A chance of showers. Mostly sunny, with a high near 64.

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: