Weather

Link to Local Radar Data

Radar

Link to Satellite Data

Satellite

National Digital Forecast Database Maximum Temperature Forecast

Max Temps

National Digital Forecast Database Weather Element Forecast

Graphical Forecast

Area Forecast Discussion

FXUS66 KMTR [Monterey CA] 251536 AFDMTR 

FXUS66 KMTR 251536
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 8:36am PDT Mon Sep 25 2017 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
836 AM PDT MON SEP 25 2017 [HEAD]

Synopsis. Warm offshore pattern will continue at least through Wednesday with mild nights and breezy winds in the hills. Some coastal cooling possible by Thursday with a gradual cooling trend back to more seasonable temperatures by next weekend but with a continued dry weather pattern. 

.SYNOPSIS...WARM OFFSHORE PATTERN WILL CONTINUE AT LEAST THROUGH
WEDNESDAY WITH MILD NIGHTS AND BREEZY WINDS IN THE HILLS. SOME
COASTAL COOLING POSSIBLE BY THURSDAY WITH A GRADUAL COOLING TREND
BACK TO MORE SEASONABLE TEMPERATURES BY NEXT WEEKEND BUT WITH A
CONTINUED DRY WEATHER PATTERN. [DISC]

Discussion. As of 08:35am PDT Monday… mainly clear skies prevail over the region again this morning as high pressure builds over the eastern Pacific. With warming conditions aloft, surface temperatures are generally running a few degrees warmer compared to 24 hours ago along with slightly lower relative humidity values. This is setting the stage for the warming trend to continue today with most areas a few to as much as 8° warmer than yesterday. With this said, the ongoing forecast for today remains on track and no updates are needed at this time. Please see the previous forecast discussion below for additional details. 

.DISCUSSION...AS OF 08:35 AM PDT MONDAY...MAINLY CLEAR SKIES
PREVAIL OVER THE REGION AGAIN THIS MORNING AS HIGH PRESSURE BUILDS
OVER THE EASTERN PACIFIC. WITH WARMING CONDITIONS ALOFT, SURFACE
TEMPERATURES ARE GENERALLY RUNNING A FEW DEGREES WARMER COMPARED
TO 24 HOURS AGO ALONG WITH SLIGHTLY LOWER RELATIVE HUMIDITY
VALUES. THIS IS SETTING THE STAGE FOR THE WARMING TREND TO
CONTINUE TODAY WITH MOST AREAS A FEW TO AS MUCH AS 8 DEGREES
WARMER THAN YESTERDAY. WITH THIS SAID, THE ONGOING FORECAST FOR
TODAY REMAINS ON TRACK AND NO UPDATES ARE NEEDED AT THIS TIME.
PLEASE SEE THE PREVIOUS FORECAST DISCUSSION BELOW FOR ADDITIONAL
DETAILS. [DISC]

Previous discussion… as of 3:37am PDT Monday. Classic September offshore weather pattern is forecast for much of the upcoming work week. Synoptic pattern features northerly wind flow aloft with a thermal trough at the surface over coastal California while the center of the surface high remains well offshore. Current surface gradients include 4 mb northerly down the coast with about 6 mb offshore from the Nevada deserts towards the coast. This is occurring with mostly clear skies to start the day. Winds in the hills are generally light this morning with lows from the mid 50s to mid 60s on average, mildest where the winds are strongest. Humidity values remain under 30% for many of the hill locations so Red Flag Warnings will continue for the North and East Bay hills through at least Wednesday. 

.PREV DISCUSSION...AS OF 3:37 AM PDT MONDAY...CLASSIC SEPTEMBER
OFFSHORE WEATHER PATTERN IS FORECAST FOR MUCH OF THE UPCOMING WORK
WEEK. SYNOPTIC PATTERN FEATURES NORTHERLY WIND FLOW ALOFT WITH A
THERMAL TROUGH AT THE SURFACE OVER COASTAL CALIFORNIA WHILE THE
CENTER OF THE SURFACE HIGH REMAINS WELL OFFSHORE. CURRENT SURFACE
GRADIENTS INCLUDE 4 MB NORTHERLY DOWN THE COAST WITH ABOUT 6 MB
OFFSHORE FROM THE NEVADA DESERTS TOWARDS THE COAST. THIS IS
OCCURRING WITH MOSTLY CLEAR SKIES TO START THE DAY. WINDS IN THE
HILLS ARE GENERALLY LIGHT THIS MORNING WITH LOWS FROM THE MID 50S
TO MID 60S ON AVERAGE, MILDEST WHERE THE WINDS ARE STRONGEST.
HUMIDITY VALUES REMAIN UNDER 30 PERCENT FOR MANY OF THE HILL
LOCATIONS SO RED FLAG WARNINGS WILL CONTINUE FOR THE NORTH AND
EAST BAY HILLS THROUGH AT LEAST WEDNESDAY. [DISC]

Expect warm to locally hot weather today through Wednesday under offshore wind regime. However, low dewpoints will keep heat indices and impacts to a minimum along with longer early fall nights allowing for night time cooling, even for buildings without altocumulus. To be clear the magnitude and overall set-up of this heat event is not nearly as extreme as what was observed at the start of September. 

EXPECT WARM TO LOCALLY HOT WEATHER TODAY THROUGH WEDNESDAY UNDER
OFFSHORE WIND REGIME. HOWEVER, LOW DEWPOINTS WILL KEEP HEAT
INDICES AND IMPACTS TO A MINIMUM ALONG WITH LONGER EARLY FALL
NIGHTS ALLOWING FOR NIGHT TIME COOLING, EVEN FOR BUILDINGS WITHOUT
AC. TO BE CLEAR THE MAGNITUDE AND OVERALL SET-UP OF THIS HEAT
EVENT IS NOT NEARLY AS EXTREME AS WHAT WAS OBSERVED AT THE START
OF SEPT. [DISC]

For tonight, the models are showing another burst of gusty northeast/east winds, strongest over the Napa and East Bay hills. Further drying of the airmass will persist right through Tuesday. The combination of hot day time temps, dry offshore winds and prolonged periods of low humidity values has prompted the Red Flag Warning to run through Wednesday. No appreciable rain has fallen and fuels remain critically dry so use extra precaution with any ignitions sources including nigh-time warming fires. 

FOR TONIGHT, THE MODELS ARE SHOWING ANOTHER BURST OF GUSTY
NORTHEAST/EAST WINDS, STRONGEST OVER THE NAPA AND EAST BAY HILLS.
FURTHER DRYING OF THE AIRMASS WILL PERSIST RIGHT THROUGH TUESDAY.
THE COMBINATION OF HOT DAY TIME TEMPS, DRY OFFSHORE WINDS AND
PROLONGED PERIODS OF LOW HUMIDITY VALUES HAS PROMPTED THE RED
FLAG WARNING TO RUN THROUGH WEDS. NO APPRECIABLE RAIN HAS FALLEN
AND FUELS REMAIN CRITICALLY DRY SO USE EXTRA PRECAUTION WITH ANY
IGNITIONS SOURCES INCLUDING NIGH-TIME WARMING FIRES. [DISC]

By Wednesday we'll lose some of the offshore/adiabatic warming but no strong onshore return is forecast so will likely squeeze another warm to hot today, even near the coast. By Thursday the ridge will finally weaken and allow for some cooling but temperatures to remain on the warm side of normal through late week and likely into the weekend as well with no rain in sight. 

BY WEDS WE`LL LOSE SOME OF THE OFFSHORE/ADIABATIC WARMING BUT NO
STRONG ONSHORE RETURN IS FORECAST SO WILL LIKELY SQUEEZE ANOTHER
WARM TO HOT TODAY, EVEN NEAR THE COAST. BY THURSDAY THE RIDGE WILL
FINALLY WEAKEN AND ALLOW FOR SOME COOLING BUT TEMPERATURES TO
REMAIN ON THE WARM SIDE OF NORMAL THROUGH LATE WEEK AND LIKELY
INTO THE WEEKEND AS WELL WITH NO RAIN IN SIGHT. [DISC]

Aviation. As of 4:30am PDT Monday… upper level ridge off the California coast extends into the Pacific Northwest. Offshore winds at 925 mb keeping the area clear of stratus. A shortwave riding over the top of the ridge will bring in some cirrus clouds from the north. 

.AVIATION...AS OF 4:30 AM PDT MONDAY...UPPER LEVEL RIDGE OFF THE
CALIFORNIA COAST EXTENDS INTO THE PACIFIC NORTHWEST. OFFSHORE
WINDS AT 925 MB KEEPING THE AREA CLEAR OF STRATUS. A SHORTWAVE
RIDING OVER THE TOP OF THE RIDGE WILL BRING IN SOME CIRRUS CLOUDS
FROM THE NORTH. [AVIA]

Vicinity of KSFO [San Francisco CA]VFR [Visual Flight Rules]. West winds to 15 kt [17 mph] after 22Z [3pm PDT]

VICINITY OF KSFO...VFR. WEST WINDS TO 15 KT AFTER 22Z. [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]

MONTEREY BAY TERMINALS...VFR. [AVI2]

Fire weather. As of 3:37am PDT Monday… Red Flag Warnings in effect through Wednesday afternoon for the North and East Bay hills. Temps will warm up and RH [Relative Humidity] values dry out again today. Expect stronger offshore winds in the hills tonight with continued lowering of humidity into Tuesday. Models show another burst of gusty northeast winds in the North and East Bay hills Tuesday night into early Wednesday. Winds will finally ease by Wednesday afternoon but by then the fuels will be very dry with low humidity and likely the hottest day of the week with widespread readings into the upper 80s and 90s. We are near the peak of Bay Area fire season and this is a classic critical fire weather pattern. 

.FIRE WEATHER...AS OF 3:37 AM PDT MONDAY...RED FLAG WARNINGS IN
EFFECT THROUGH WEDS AFTERNOON FOR THE NORTH AND EAST BAY HILLS.
TEMPS WILL WARM UP AND RH VALUES DRY OUT AGAIN TODAY. EXPECT
STRONGER OFFSHORE WINDS IN THE HILLS TONIGHT WITH CONTINUED
LOWERING OF HUMIDITY INTO TUESDAY. MODELS SHOW ANOTHER BURST OF
GUSTY NORTHEAST WINDS IN THE NORTH AND EAST BAY HILLS TUESDAY
NIGHT INTO EARLY WEDS. WINDS WILL FINALLY EASE BY WEDS AFTERNOON
BUT BY THEN THE FUELS WILL BE VERY DRY WITH LOW HUMIDITY AND
LIKELY THE HOTTEST DAY OF THE WEEK WITH WIDESPREAD READINGS INTO
THE UPPER 80S AND 90S. WE ARE NEAR THE PEAK OF BAY AREA FIRE
SEASON AND THIS IS A CLASSIC CRITICAL FIRE WEATHER PATTERN. [AVIA]

Marine. As of 08:35am PDT Monday… moderate northwesterly winds will continue over the northern outer waters as high pressure sits over the eastern Pacific and a thermal trough resides over California. Winds will begin to decrease on Tuesday as the trough shifts towards the coast. 

.MARINE...AS OF 08:35 AM PDT MONDAY...MODERATE NORTHWESTERLY WINDS
WILL CONTINUE OVER THE NORTHERN OUTER WATERS AS HIGH PRESSURE SITS
OVER THE EASTERN PACIFIC AND A THERMAL TROUGH RESIDES OVER
CALIFORNIA. WINDS WILL BEGIN TO DECREASE ON TUESDAY AS THE TROUGH
SHIFTS TOWARDS THE COAST. [AVIA]

MTR Watches/Warnings/Advisories

  • Today: Small Craft AdvisoryPt Arena [Mendocino CA] to Pigeon Pt [Pescadero CA] 10–60 nm [69 miles] 
.MTR WATCHES/WARNINGS/ADVISORIES...
.TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM [WARN]

Public Forecast: Rgass; Aviation: W PI; Marine: AS; Fire Weather: RWW 

PUBLIC FORECAST: RGASS
AVIATION: W PI
MARINE: AS
FIRE WEATHER: RWW [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

25 Sep 9:15am PDT

Today Sunny, with a high near 76°. Calm wind becoming WNW 5 to 9 mph in the afternoon.
Tonight Mostly clear, with a low around 55°. WNW wind 5 to 10 mph.
Tuesday Sunny, with a high near 74°. Calm wind becoming NNW 5 to 7 mph in the afternoon.
Tuesday Night Clear, with a low around 57°. WNW wind 5 to 7 mph becoming calm in the evening.
Wednesday Sunny, with a high near 75°. Light and variable wind.
Wednesday Night Mostly clear, with a low around 57°.
Thursday Sunny, with a high near 73°.
Thursday Night Mostly clear, with a low around 56°.
Friday Sunny, with a high near 68°.
Friday Night Mostly clear, with a low around 55°.
Saturday Sunny, with a high near 70°.
Saturday Night Mostly clear, with a low around 55°.
Sunday Sunny, with a high near 72°.
Today
Sunny, with a high near 76. Calm wind becoming west northwest 5 to 9 mph in the afternoon.
Tonight
Mostly clear, with a low around 55. West northwest wind 5 to 10 mph.
Tuesday
Sunny, with a high near 74. Calm wind becoming north northwest 5 to 7 mph in the afternoon.
Tuesday Night
Clear, with a low around 57. West northwest wind 5 to 7 mph becoming calm in the evening.
Wednesday
Sunny, with a high near 75. Light and variable wind.
Wednesday Night
Mostly clear, with a low around 57.
Thursday
Sunny, with a high near 73.
Thursday Night
Mostly clear, with a low around 56.
Friday
Sunny, with a high near 68.
Friday Night
Mostly clear, with a low around 55.
Saturday
Sunny, with a high near 70.
Saturday Night
Mostly clear, with a low around 55.
Sunday
Sunny, with a high near 72.

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: