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Area Forecast Discussion

FXUS66 KMTR [Monterey CA] 260553 AFDMTR 

FXUS66 KMTR 260553
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 9:53pm PST Tue Feb 25 2020 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
953 PM PST TUE FEB 25 2020 [HEAD]

Synopsis. Unseasonably mild and dry conditions will persist over the region through the remainder of February. A weather system will approach from the northwest this upcoming weekend, bringing cooler temperatures and the potential for light precipitation. 

.SYNOPSIS...UNSEASONABLY MILD AND DRY CONDITIONS WILL PERSIST OVER
THE REGION THROUGH THE REMAINDER OF FEBRUARY. A WEATHER SYSTEM WILL
APPROACH FROM THE NORTHWEST THIS UPCOMING WEEKEND, BRINGING COOLER
TEMPERATURES AND THE POTENTIAL FOR LIGHT PRECIPITATION. [DISC]

Discussion. As of 9:40pm PST Tuesday… no significant updates this evening. Thin high clouds are rotating around the upper ridge with temps still hovering near 60 in many locations, unseasonably mild after a very warm February afternoon. 9pm reading of 65 in the City is noteworthy while SFO [San Francisco CA] broke its record high for the day with an afternoon high of 76 breaking the old record of 74 back in 1992. 

.DISCUSSION...AS OF 9:40 PM PST TUESDAY...NO SIGNIFICANT UPDATES
THIS EVENING. THIN HIGH CLOUDS ARE ROTATING AROUND THE UPPER RIDGE
WITH TEMPS STILL HOVERING NEAR 60 IN MANY LOCATIONS, UNSEASONABLY
MILD AFTER A VERY WARM FEBRUARY AFTERNOON. 9 PM READING OF 65 IN
THE CITY IS NOTEWORTHY WHILE SFO BROKE ITS RECORD HIGH FOR THE DAY
WITH AN AFTERNOON HIGH OF 76 BREAKING THE OLD RECORD OF 74 BACK
IN 1992. [DISC]

Northerly gradient from Arcata to SFO [San Francisco CA] is still a healthy 5–6 mb along with offshore from Winnemucca [NW Nevada] to San Francisco of around 10 mb all of which should be sufficient to keep any stratus/fog from forming overnight. 

NORTHERLY GRADIENT FROM ARCATA TO SFO IS STILL A HEALTHY 5-6 MB
ALONG WITH OFFSHORE FROM WMC TO SFO OF AROUND 10 MB ALL OF WHICH
SHOULD BE SUFFICIENT TO KEEP ANY STRATUS/FOG FROM FORMING
OVERNIGHT. [DISC]

Offshore flow will ease slightly the next few days which should keep us out of record territory but days will continue to be mild to warm with mostly sunny skies Wednesday through Friday with highs mainly in the 70s regionwide. 

OFFSHORE FLOW WILL EASE SLIGHTLY THE NEXT FEW DAYS WHICH SHOULD
KEEP US OUT OF RECORD TERRITORY BUT DAYS WILL CONTINUE TO BE MILD
TO WARM WITH MOSTLY SUNNY SKIES WEDS THROUGH FRIDAY WITH HIGHS
MAINLY IN THE 70S REGIONWIDE. [DISC]

Saturday will remain dry but much cooler as onshore winds increase ahead of the next front as clouds increase. The models have been pretty consistent in generating upslope precipitation over the Sierra with upper level divergence on Sunday while the parent low looks like it wants to stay offshore. The airmass aloft will be much cooler with 850 mb temps from –2 to –4°C. This should lead to lots of cold air cumulus and scattered rain showers across the region for Sunday. The convective nature suggests not all locations will see precipitation on Sunday though cooler temperatures will be felt regionwide with highs only in the 50s or about 20° of cooling from the midweek warm spell. 

SATURDAY WILL REMAIN DRY BUT MUCH COOLER AS ONSHORE WINDS INCREASE
AHEAD OF THE NEXT FRONT AS CLOUDS INCREASE. THE MODELS HAVE BEEN
PRETTY CONSISTENT IN GENERATING UPSLOPE PRECIP OVER THE SIERRA
WITH UPPER LEVEL DIVERGENCE ON SUNDAY WHILE THE PARENT LOW LOOKS
LIKE IT WANTS TO STAY OFFSHORE. THE AIRMASS ALOFT WILL BE MUCH
COOLER WITH 850 MB TEMPS FROM -2 TO -4 CELSIUS. THIS SHOULD LEAD
TO LOTS OF COLD AIR CUMULUS AND SCATTERED RAIN SHOWERS ACROSS THE
REGION FOR SUNDAY. THE CONVECTIVE NATURE SUGGESTS NOT ALL
LOCATIONS WILL SEE PRECIP ON SUNDAY THOUGH COOLER TEMPERATURES
WILL BE FELT REGIONWIDE WITH HIGHS ONLY IN THE 50S OR ABOUT 20
DEGREES OF COOLING FROM THE MIDWEEK WARM SPELL. [DISC]

High pressure builds in by Monday/Tuesday with a return of dry and mild weather. The long range patterns want to build in a negative PNA [Pacific North American. The PNA pattern features changes in the strength and position of the jet stream and storminess over the eastern North Pacific and North America. The positive phase of the PNA is often associated with weak El Niño episodes.] with some type of troughing over the west as the models hint at perhaps some more rain chances by the first full weekend of March. However, confidence remains low as we transition from a very dry February and hope for some March rains. 

HIGH PRESSURE BUILDS IN BY MONDAY/TUESDAY WITH A RETURN OF DRY AND
MILD WEATHER. THE LONG RANGE PATTERNS WANT TO BUILD IN A NEGATIVE
PNA WITH SOME TYPE OF TROUGHING OVER THE WEST AS THE MODELS HINT
AT PERHAPS SOME MORE RAIN CHANCES BY THE FIRST FULL WEEKEND OF
MARCH. HOWEVER, CONFIDENCE REMAINS LOW AS WE TRANSITION FROM A
VERY DRY FEBRUARY AND HOPE FOR SOME MARCH RAINS. [DISC]

Previous discussion… as of 01:58pm PST Tuesday. Offshore flow over the region this afternoon has allowed for temperatures to be 5 to as much as 15° warmer compared to this time yesterday. Meanwhile, light onshore flow near the coast has allowed for some cooling with many locations coastal areas reaching their maximum temperature before noon. With this pattern, look for overnight lows to drop into the 40s tonight under mostly clear sky conditions while 50s will be more common in the region's higher elevations. 

.PREV DISCUSSION...AS OF 01:58 PM PST TUESDAY...OFFSHORE FLOW OVER THE
REGION THIS AFTERNOON HAS ALLOWED FOR TEMPERATURES TO BE 5 TO AS
MUCH AS 15 DEGREES WARMER COMPARED TO THIS TIME YESTERDAY.
MEANWHILE, LIGHT ONSHORE FLOW NEAR THE COAST HAS ALLOWED FOR SOME
COOLING WITH MANY LOCATIONS COASTAL AREAS REACHING THEIR MAXIMUM
TEMPERATURE BEFORE NOON. WITH THIS PATTERN, LOOK FOR OVERNIGHT
LOWS TO DROP INTO THE 40S TONIGHT UNDER MOSTLY CLEAR SKY
CONDITIONS WHILE 50S WILL BE MORE COMMON IN THE REGION`S HIGHER
ELEVATIONS. [DISC]

A ridge of high pressure and weak offshore flow is likely to persist through much of the remainder of the week. This will keep temperatures well above seasonal averages during both the daytime and overnight. Look for 70s for most locations each afternoon with some isolated interior spots reaching 80°F with widespread 40s for overnight/morning lows. 

A RIDGE OF HIGH PRESSURE AND WEAK OFFSHORE FLOW IS LIKELY TO PERSIST
THROUGH MUCH OF THE REMAINDER OF THE WEEK. THIS WILL KEEP
TEMPERATURES WELL ABOVE SEASONAL AVERAGES DURING BOTH THE DAYTIME
AND OVERNIGHT. LOOK FOR 70S FOR MOST LOCATIONS EACH AFTERNOON WITH
SOME ISOLATED INTERIOR SPOTS REACHING 80 DEG F WITH WIDESPREAD 40S
FOR OVERNIGHT/MORNING LOWS. [DISC]

The ridge will begin to weaken on Friday as a mid/upper level trough approaches the region from the northwest. While temperatures may cool slightly on Friday, the greatest drop will occur on Saturday when Max temperatures drop by around 10°F for most locations. Chances for precipitation remain in the forecast from late Saturday night into Sunday as the main trough axis drops southward across the region. However, both deterministic and ensemble members have trended drier for the San Francisco Bay Area and Central Coast as this system moves across the region. Regardless, widespread beneficial rainfall is not anticipated at this time. 

THE RIDGE WILL BEGIN TO WEAKEN ON FRIDAY AS A MID/UPPER LEVEL TROUGH
APPROACHES THE REGION FROM THE NORTHWEST. WHILE TEMPERATURES MAY
COOL SLIGHTLY ON FRIDAY, THE GREATEST DROP WILL OCCUR ON SATURDAY
WHEN MAX TEMPERATURES DROP BY AROUND 10 DEG F FOR MOST LOCATIONS.
CHANCES FOR PRECIPITATION REMAIN IN THE FORECAST FROM LATE SATURDAY
NIGHT INTO SUNDAY AS THE MAIN TROUGH AXIS DROPS SOUTHWARD ACROSS THE
REGION. HOWEVER, BOTH DETERMINISTIC AND ENSEMBLE MEMBERS HAVE
TRENDED DRIER FOR THE SAN FRANCISCO BAY AREA AND CENTRAL COAST AS
THIS SYSTEM MOVES ACROSS THE REGION. REGARDLESS, WIDESPREAD
BENEFICIAL RAINFALL IS NOT ANTICIPATED AT THIS TIME. [DISC]

Aviation. As of 9:52pm PST Tuesday… for 06Z [10pm PST] TAFs [Terminal Aerodrome Forecasts]. Mostly clear skies over the region tonight. Winds have become light which will remain through the morning. Expect breezier conditions in the afternoon. Skies are expected to remain clear with occasional high clouds. 

.AVIATION...AS OF 9:52 PM PST TUESDAY...FOR 06Z TAFS. MOSTLY
CLEAR SKIES OVER THE REGION TONIGHT. WINDS HAVE BECOME LIGHT WHICH
WILL REMAIN THROUGH THE MORNING. EXPECT BREEZIER CONDITIONS IN THE
AFTERNOON. SKIES ARE EXPECTED TO REMAIN CLEAR WITH OCCASIONAL
HIGH CLOUDS. [AVIA]

Vicinity of KSFO [San Francisco CA]VFR [Visual Flight Rules]. Winds have become light and variable. VFR [Visual Flight Rules] conditions are forecast through the night night and prevail through Wednesday afternoon. Breezier winds forecast in the afternoon. 

VICINITY OF KSFO...VFR. WINDS HAVE BECOME LIGHT AND VARIABLE.
VFR CONDITIONS ARE FORECAST THROUGH THE NIGHT NIGHT AND PREVAIL
THROUGH WEDNESDAY AFTERNOON. BREEZIER WINDS FORECAST IN THE
AFTERNOON. [AVI2]

SFO [San Francisco CA] bridge approach… similar to the terminal. 

SFO BRIDGE APPROACH...SIMILAR TO THE TERMINAL. [AVI2]

Monterey Bay terminals… VFR [Visual Flight Rules]. Winds are light a few breezier spots along the coast. There still remains a low confidence chance of low clouds near coastal terminals. Wednesday is forecast to be VFR [Visual Flight Rules] with light winds, breezier in the afternoon. 

MONTEREY BAY TERMINALS...VFR. WINDS ARE LIGHT A FEW BREEZIER SPOTS
ALONG THE COAST. THERE STILL REMAINS A LOW CONFIDENCE CHANCE OF
LOW CLOUDS NEAR COASTAL TERMINALS. WEDNESDAY IS FORECAST TO BE
VFR WITH LIGHT WINDS, BREEZIER IN THE AFTERNOON. [AVI2]

Marine. As of 08:22pm PST Tuesday… northwest winds continue to subside but winds gusts will prevail for the outer waters north of Point Reyes [San Francisco CA] through the overnight hours. A longer period northwest swell passes by midweek as winds weaken. Winds and seas will increase later this weekend as the next storm approaches from the Pacific Northwest. 

.MARINE...AS OF 08:22 PM PST TUESDAY...NORTHWEST WINDS CONTINUE
TO SUBSIDE BUT WINDS GUSTS WILL PREVAIL FOR THE OUTER WATERS NORTH
OF POINT REYES THROUGH THE OVERNIGHT HOURS. A LONGER PERIOD
NORTHWEST SWELL PASSES BY MIDWEEK AS WINDS WEAKEN. WINDS AND SEAS
WILL INCREASE LATER THIS WEEKEND AS THE NEXT STORM APPROACHES FROM
THE PACIFIC NORTHWEST. [AVIA]

MTR Watches/Warnings/Advisories

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

Public Forecast: RWW; Aviation: DK; Marine: DK 

PUBLIC FORECAST: RWW
AVIATION: DK
MARINE: DK [CRED]
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK]

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Point Forecast

Half Moon Bay CA

21 Feb 04:00pm PST

Overnight Mostly clear, with a steady temperature around 52°. ENE wind around 8 mph.
Wednesday Sunny, with a high near 70°. Light and variable wind becoming SW around 5 mph in the morning.
Wednesday Night Mostly clear, with a low around 45°. Calm wind.
Thursday Sunny, with a high near 71°. ENE wind 5 to 9 mph becoming calm in the afternoon.
Thursday Night Partly cloudy, with a low around 48°. ENE wind around 9 mph.
Friday Partly sunny, with a high near 69°.
Friday Night Mostly cloudy, with a low around 46°.
Saturday Partly sunny, with a high near 59°.
Saturday Night A chance of rain after 10pm. Mostly cloudy, with a low around 43°.
Sunday A chance of rain. Mostly sunny, with a high near 56°.
Sunday Night Partly cloudy, with a low around 41°.
Monday Sunny, with a high near 61°.
Monday Night Mostly clear, with a low around 44°.
Tuesday Sunny, with a high near 63°.
Overnight
Mostly clear, with a steady temperature around 52. East northeast wind around 8 mph.
Wednesday
Sunny, with a high near 70. Light and variable wind becoming southwest around 5 mph in the morning.
Wednesday Night
Mostly clear, with a low around 45. Calm wind.
Thursday
Sunny, with a high near 71. East northeast wind 5 to 9 mph becoming calm in the afternoon.
Thursday Night
Partly cloudy, with a low around 48. East northeast wind around 9 mph.
Friday
Partly sunny, with a high near 69.
Friday Night
Mostly cloudy, with a low around 46.
Saturday
Partly sunny, with a high near 59.
Saturday Night
A chance of rain after 10pm. Mostly cloudy, with a low around 43.
Sunday
A chance of rain. Mostly sunny, with a high near 56.
Sunday Night
Partly cloudy, with a low around 41.
Monday
Sunny, with a high near 61.
Monday Night
Mostly clear, with a low around 44.
Tuesday
Sunny, with a high near 63.

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: