Area Forecast Discussion
FXUS66 KMTR [Monterey CA] 271822 AFDMTR ∨
FXUS66 KMTR 271822 AFDMTR [HEAD]
National Weather Service San Francisco California 11:22am PDT Wed Sep 27 2023 ∨
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO CA 1122 AM PDT WED SEP 27 2023 [HEAD]
New aviation, marine. ∨
...NEW AVIATION, MARINE... [DISC]
Synopsis. Issued at 2:15am PDT Wednesday September 27 2023 ∨
.SYNOPSIS... ISSUED AT 215 AM PDT WED SEP 27 2023 [DISC]
Overall quiet weather in store through the end of the week with breezy afternoons and evenings. Beach hazards statement in effect this afternoon as elevated surf may still be dangerous for beach goers. Upper low dips down into California this weekend, which may bring isolated, slight precipitation chances as well as cooler temperatures. ∨
OVERALL QUIET WEATHER IN STORE THROUGH THE END OF THE WEEK WITH BREEZY AFTERNOONS AND EVENINGS. BEACH HAZARDS STATEMENT IN EFFECT THIS AFTERNOON AS ELEVATED SURF MAY STILL BE DANGEROUS FOR BEACH GOERS. UPPER LOW DIPS DOWN INTO CA THIS WEEKEND, WHICH MAY BRING ISOLATED, SLIGHT PRECIP CHANCES AS WELL AS COOLER TEMPERATURES. [DISC]
Short term. (today and tonight) issued at 2:15am PDT Wednesday September 27 2023 ∨
.SHORT TERM... (TODAY AND TONIGHT) ISSUED AT 215 AM PDT WED SEP 27 2023 [DISC]
Nighttime satellite imagery is relatively clear/quiet early this AM with limited coastal stratus coverage. Low clouds will struggle to redevelop overnight and any that does will stay confined to the coastline as marine layer inversion is not really present (00Z [5pm PDT] sounding shows weak inversion around 6000 feet). Cold air advecting into the area overnight won't help to re-establish the marine layer either. However, we could see some patchy fog may develop in the hills tonight thanks to clear skies aiding in radiative cooling, lowering dew point depressions. ∨
NIGHTTIME SATELLITE IMAGERY IS RELATIVELY CLEAR/QUIET EARLY THIS AM WITH LIMITED COASTAL STRATUS COVERAGE. LOW CLOUDS WILL STRUGGLE TO REDEVELOP OVERNIGHT AND ANY THAT DOES WILL STAY CONFINED TO THE COASTLINE AS MARINE LAYER INVERSION IS NOT REALLY PRESENT (00Z SOUNDING SHOWS WEAK INVERSION AROUND 6000 FEET). COLD AIR ADVECTING INTO THE AREA OVERNIGHT WON`T HELP TO RE-ESTABLISH THE MARINE LAYER EITHER. HOWEVER, WE COULD SEE SOME PATCHY FOG MAY DEVELOP IN THE HILLS TONIGHT THANKS TO CLEAR SKIES AIDING IN RADIATIVE COOLING, LOWERING DEW POINT DEPRESSIONS. [DISC]
Generally nice weather expected for the day today with clear conditions and near seasonable temperatures. Highs today near the coast will be in the mid 60s, bayside in the low to mid 70s, and further inland in the low 80s. Breezy to locally gusty conditions looking probable tomorrow as both onshore and northerly gradients will increase during the afternoon/evening as strong low pressure (which is currently offshore the Pacific Northwest) moves inland into the N Rockies today. ∨
GENERALLY NICE WEATHER EXPECTED FOR THE DAY TODAY WITH CLEAR CONDITIONS AND NEAR SEASONABLE TEMPERATURES. HIGHS TODAY NEAR THE COAST WILL BE IN THE MID 60S, BAYSIDE IN THE LOW TO MID 70S, AND FURTHER INLAND IN THE LOW 80S. BREEZY TO LOCALLY GUSTY CONDITIONS LOOKING PROBABLE TOMORROW AS BOTH ONSHORE AND NORTHERLY GRADIENTS WILL INCREASE DURING THE AFTERNOON/EVENING AS STRONG LOW PRESSURE (WHICH IS CURRENTLY OFFSHORE THE PACIFIC NW) MOVES INLAND INTO THE N ROCKIES TODAY. [DISC]
In addition, large breaking waves and increased rip current risk still continues along the coastline. The large NW swell is diminishing and no longer meets High Surf Advisory criteria, but elevated surf still possible today so beach hazards statement is now in effect through the afternoon today. See beaches for more. ∨
IN ADDITION, LARGE BREAKING WAVES AND INCREASED RIP CURRENT RISK STILL CONTINUES ALONG THE COASTLINE. THE LARGE NW SWELL IS DIMINISHING AND NO LONGER MEETS HIGH SURF ADVISORY CRITERIA, BUT ELEVATED SURF STILL POSSIBLE TODAY SO BEACH HAZARDS STATEMENT IS NOW IN EFFECT THROUGH THE AFTERNOON TODAY. SEE BEACHES FOR MORE. [DISC]
Long term. (Thursday through Tuesday) issued at 2:15am PDT Wednesday September 27 2023 ∨
.LONG TERM... (THURSDAY THROUGH TUESDAY) ISSUED AT 215 AM PDT WED SEP 27 2023 [DISC]
Slightly warmer temperatures expected Thursday across the interior. Breezy onshore flow continues during the afternoon/evening. ∨
SLIGHTLY WARMER TEMPERATURES EXPECTED THURSDAY ACROSS THE INTERIOR. BREEZY ONSHORE FLOW CONTINUES DURING THE AFTERNOON/EVENING. [DISC]
By late Friday into Saturday, an upper low will dig southward from the Pacific Northwest into California. The latest runs of 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 Euro [European Center for Medium-Range Weather Forecasts model] (and their ensembles) have shifted the trough axis more westerly when it dips south, which would favor wetter conditions and onshore flow. The official forecast now features a slight chance for rain Friday into Saturday, mostly across coastal terrain and the interior portion of the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map]. For example, guidance for Livermore Airport shows a majority of its 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] ensemble members showing light precipitation accumulations this weekend. However, the trajectory of the low could still change, which would affect precipitation chances, so stay tuned. Temperatures this weekend will be cooler as this upper low brings in a cooler airmass. ∨
BY LATE FRIDAY INTO SATURDAY, AN UPPER LOW WILL DIG SOUTHWARD FROM THE PACIFIC NW INTO CA. THE LATEST RUNS OF GFS AND EURO (AND THEIR ENSEMBLES) HAVE SHIFTED THE TROUGH AXIS MORE WESTERLY WHEN IT DIPS SOUTH, WHICH WOULD FAVOR WETTER CONDITIONS AND ONSHORE FLOW. THE OFFICIAL FORECAST NOW FEATURES A SLIGHT CHANCE FOR RAIN FRIDAY INTO SATURDAY, MOSTLY ACROSS COASTAL TERRAIN AND THE INTERIOR PORTION OF THE CWA. FOR EXAMPLE, GUIDANCE FOR LIVERMORE AIRPORT SHOWS A MAJORITY OF ITS GFS AND ECMWF ENSEMBLE MEMBERS SHOWING LIGHT PRECIP ACCUMULATIONS THIS WEEKEND. HOWEVER, THE TRAJECTORY OF THE LOW COULD STILL CHANGE, WHICH WOULD AFFECT PRECIP CHANCES, SO STAY TUNED. TEMPERATURES THIS WEEKEND WILL BE COOLER AS THIS UPPER LOW BRINGS IN A COOLER AIRMASS. [DISC]
As trough exits east Sun into next week, could still see some northerly winds across the interior. Will continue to monitor as details become clearer in coming days. ∨
AS TROUGH EXITS EAST SUN INTO NEXT WEEK, COULD STILL SEE SOME NORTHERLY WINDS ACROSS THE INTERIOR. WILL CONTINUE TO MONITOR AS DETAILS BECOME CLEARER IN COMING DAYS. [DISC]
Aviation. (18Z [11am PDT] TAFs [Terminal Aerodrome Forecasts]) issued at 11:20am PDT Wednesday September 27 2023 ∨
.AVIATION... (18Z TAFS) ISSUED AT 1120 AM PDT WED SEP 27 2023 [AVIA]
VFR [Visual Flight Rules] conditions across the Bay Area expected to continue throughout the afternoon. Ceilings are expected to return overnight for MRY [Monterey CA] and SNS [Salinas CA] but should begin clearing by 17Z [10am PDT] tomorrow. Persistence forecast for the North Bay suggests a possibility of fog and reduced visibility overnight however this is fairly low confidence. Breezy winds are expected throughout the Bay Area during the afternoon but will weaken overnight. ∨
VFR CONDITIONS ACROSS THE BAY AREA EXPECTED TO CONTINUE THROUGHOUT THE AFTERNOON. CEILINGS ARE EXPECTED TO RETURN OVERNIGHT FOR MRY AND SNS BUT SHOULD BEGIN CLEARING BY 17Z TOMORROW. PERSISTENCE FORECAST FOR THE NORTH BAY SUGGESTS A POSSIBILITY OF FOG AND REDUCED VISIBILITY OVERNIGHT HOWEVER THIS IS FAIRLY LOW CONFIDENCE. BREEZY WINDS ARE EXPECTED THROUGHOUT THE BAY AREA DURING THE AFTERNOON BUT WILL WEAKEN OVERNIGHT. [AVI2]
Vicinity of SFO [San Francisco CA]… VFR [Visual Flight Rules] conditions through the rest of the TAF [Terminal Aerodrome Forecast] period. Gusts up to 30 kts [35 mph] at SFO [San Francisco CA] and 25 kts [29 mph] at OAK [Oakland CA] are possible during the afternoon. Windy conditions will weaken overnight around 05Z [10pm PDT] for OAK [Oakland CA] and 09Z [2am PDT] for SFO [San Francisco CA] before increasing slightly tomorrow afternoon. Some cloud cover may move in overnight/into the early morning for SFO [San Francisco CA] and OAK [Oakland CA] but guidance suggests moderate confidence that cloud cover will stay few to scattered. ∨
VICINITY OF SFO...VFR CONDITIONS THROUGH THE REST OF THE TAF PERIOD. GUSTS UP TO 30KTS AT SFO AND 25KTS AT OAK ARE POSSIBLE DURING THE AFTERNOON. WINDY CONDITIONS WILL WEAKEN OVERNIGHT AROUND 05Z FOR OAK AND 09Z FOR SFO BEFORE INCREASING SLIGHTLY TOMORROW AFTERNOON. SOME CLOUD COVER MAY MOVE IN OVERNIGHT/INTO THE EARLY MORNING FOR SFO AND OAK BUT GUIDANCE SUGGESTS MODERATE CONFIDENCE THAT CLOUD COVER WILL STAY FEW TO SCATTERED. [AVI2]
SFO [San Francisco CA] bridge approach… similar to SFO [San Francisco CA] ∨
SFO BRIDGE APPROACH...SIMILAR TO SFO [AVI2]
Monterey Bay terminals… VFR [Visual Flight Rules] conditions to prevail through the afternoon. MVFR [Marginal Visual Flight Rules] conditions will return overnight for MRY [Monterey CA] around 07Z [12am PDT] and SNS [Salinas CA] around 13Z [6am PDT] but cloud cover should begin to clear at 17Z [10am PDT] tomorrow. Model guidance was split on the timing of cloud cover return for MRY [Monterey CA] with some models indicating as early as 02Z [7pm PDT] and others closer to 12Z [5am PDT]. Moderate confidence that some scattered clouds will return closer to 04Z [9pm PDT] and become broken later in the period. Afternoon winds will be breezier with SNS [Salinas CA] potentially gusting up to 15 kts [17 mph]. ∨
MONTEREY BAY TERMINALS...VFR CONDITIONS TO PREVAIL THROUGH THE AFTERNOON. MVFR CONDITIONS WILL RETURN OVERNIGHT FOR MRY AROUND 07Z AND SNS AROUND 13Z BUT CLOUD COVER SHOULD BEGIN TO CLEAR AT 17Z TOMORROW. MODEL GUIDANCE WAS SPLIT ON THE TIMING OF CLOUD COVER RETURN FOR MRY WITH SOME MODELS INDICATING AS EARLY AS 02Z AND OTHERS CLOSER TO 12Z. MODERATE CONFIDENCE THAT SOME SCATTERED CLOUDS WILL RETURN CLOSER TO 04Z AND BECOME BROKEN LATER IN THE PERIOD. AFTERNOON WINDS WILL BE BREEZIER WITH SNS POTENTIALLY GUSTING UP TO 15KTS. [AVI2]
Marine. (today through Monday) issued at 11:20am PDT Wednesday September 27 2023 ∨
.MARINE... (TODAY THROUGH MONDAY) ISSUED AT 1120 AM PDT WED SEP 27 2023 [AVIA]
Fresh to strong northwesterly winds continue with winds becoming strong to near gale into this afternoon, with gale-force conditions developing by this evening for much of the outer waters along with favored coastal jet regions. Large northwest swell continues to slowly diminish through the next couple of days, but large wind waves begin to build overnight tonight and persist through the weekend. Both winds and waves will combine to create dangerous conditions for small craft through the remainder of the week. ∨
FRESH TO STRONG NORTHWESTERLY WINDS CONTINUE WITH WINDS BECOMING STRONG TO NEAR GALE INTO THIS AFTERNOON, WITH GALE-FORCE CONDITIONS DEVELOPING BY THIS EVENING FOR MUCH OF THE OUTER WATERS ALONG WITH FAVORED COASTAL JET REGIONS. LARGE NORTHWEST SWELL CONTINUES TO SLOWLY DIMINISH THROUGH THE NEXT COUPLE OF DAYS, BUT LARGE WIND WAVES BEGIN TO BUILD OVERNIGHT TONIGHT AND PERSIST THROUGH THE WEEKEND. BOTH WINDS AND WAVES WILL COMBINE TO CREATE DANGEROUS CONDITIONS FOR SMALL CRAFT THROUGH THE REMAINDER OF THE WEEK. [AVI2]
Beaches… issued at 2:15am PDT Wednesday September 27 2023 ∨
.BEACHES... ISSUED AT 215 AM PDT WED SEP 27 2023 [DISC]
NW swell continues to move through the coastal waters and will diminish through the day today. Currently, the swell is around 10–11 feet at 14 seconds. The High Surf Advisory was allowed to expire, but was replaced by a beach hazards statement to account for lingering dangerous conditions. Large breaking waves still possible around 12–15 feet. Coastal buoys as of 2am continue to show elevated seas with significant wave heights around 12–14 feet at 14 seconds. ∨
NW SWELL CONTINUES TO MOVE THROUGH THE COASTAL WATERS AND WILL DIMINISH THROUGH THE DAY TODAY. CURRENTLY, THE SWELL IS AROUND 10 TO 11 FEET AT 14 SECONDS. THE HIGH SURF ADVISORY WAS ALLOWED TO EXPIRE, BUT WAS REPLACED BY A BEACH HAZARDS STATEMENT TO ACCOUNT FOR LINGERING DANGEROUS CONDITIONS. LARGE BREAKING WAVES STILL POSSIBLE AROUND 12 TO 15 FEET. COASTAL BUOYS AS OF 2 AM CONTINUE TO SHOW ELEVATED SEAS WITH SIGNIFICANT WAVE HEIGHTS AROUND 12-14 FEET AT 14 SECONDS. [DISC]
Continue to exercise caution even though the High Surf Advisory has ended, as energy in the ocean can be slow to diminish and large waves may continue to be present afterwards until fully dissipated. ∨
CONTINUE TO EXERCISE CAUTION EVEN THOUGH THE HIGH SURF ADVISORY HAS ENDED, AS ENERGY IN THE OCEAN CAN BE SLOW TO DIMINISH AND LARGE WAVES MAY CONTINUE TO BE PRESENT AFTERWARDS UNTIL FULLY DISSIPATED. [DISC]
.MTR WATCHES/WARNINGS/ADVISORIES... CA...BEACH HAZARDS STATEMENT UNTIL 5 PM PDT THIS AFTERNOON FOR CAZ006- 505-509-529-530. [WARN]
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM PDT THIS EVENING FOR PZZ530. [WRN2]
SMALL CRAFT ADVISORY UNTIL 3 AM PDT THURSDAY FOR PZZ535-560. [WRN2]
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 PM PDT THURSDAY FOR PZZ540. [WRN2]
GALE WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY EVENING FOR PZZ540-560. [WRN2]
SMALL CRAFT ADVISORY UNTIL 3 PM PDT THURSDAY FOR PZZ545. [WRN2]
GALE WARNING UNTIL 3 AM PDT FRIDAY FOR PZZ565. [WRN2]
SMALL CRAFT ADVISORY UNTIL 3 PM PDT THIS AFTERNOON FOR PZZ570. [WRN2]
GALE WARNING FROM 3 PM THIS AFTERNOON TO 3 PM PDT THURSDAY FOR PZZ570. [WRN2]
SMALL CRAFT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR PZZ575. [WRN2]
GALE WARNING FROM 9 PM THIS EVENING TO 3 PM PDT THURSDAY FOR PZZ575. [WRN2]
SHORT TERM...MCCORKLE LONG TERM....MCCORKLE AVIATION...KENNEDY MARINE...CW [WRN2]
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Half Moon Bay CA
27 Sep 01:55pm PDT
This Afternoon Mostly sunny, with a high near 69°. Breezy, with a NW wind 18 to 23 mph, with gusts as high as 28 mph.
Tonight Partly cloudy, with a low around 51°. Breezy, with a NW wind 17 to 22 mph decreasing to 6 to 11 mph after midnight. Winds could gust as high as 26 mph.
Thursday Mostly sunny, with a high near 67°. North wind 5 to 14 mph becoming west in the afternoon.
Thursday Night Mostly clear, with a low around 53°. NW wind 13 to 17 mph, with gusts as high as 22 mph.
Friday Mostly sunny, with a high near 66°. NW wind 14 to 20 mph, with gusts as high as 24 mph.
Friday Night Mostly cloudy, with a low around 52°.
Saturday Partly sunny, with a high near 63°.
Saturday Night Partly cloudy, with a low around 50°.
Sunday Mostly sunny, with a high near 66°.
Sunday Night Mostly cloudy, with a low around 50°.
Monday Mostly sunny, with a high near 67°.
Monday Night Partly cloudy, with a low around 51°.
Tuesday Mostly sunny, with a high near 70°.
Mostly sunny, with a high near 69. Breezy, with a northwest wind 18 to 23 mph, with gusts as high as 28 mph.
Partly cloudy, with a low around 51. Breezy, with a northwest wind 17 to 22 mph decreasing to 6 to 11 mph after midnight. Winds could gust as high as 26 mph.
Mostly sunny, with a high near 67. North wind 5 to 14 mph becoming west in the afternoon.
Mostly clear, with a low around 53. Northwest wind 13 to 17 mph, with gusts as high as 22 mph.
Mostly sunny, with a high near 66. Northwest wind 14 to 20 mph, with gusts as high as 24 mph.
Mostly cloudy, with a low around 52.
Partly sunny, with a high near 63.
Partly cloudy, with a low around 50.
Mostly sunny, with a high near 66.
Mostly cloudy, with a low around 50.
Mostly sunny, with a high near 67.
Partly cloudy, with a low around 51.
Mostly sunny, with a high near 70.