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FXUS66 KMTR [Monterey CA] 211735 AFDMTR 

FXUS66 KMTR 211735
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 9:35am PST Tue Nov 21 2017 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
935 AM PST TUE NOV 21 2017 [HEAD]

Synopsis. High pressure will bring dry and warmer weather to the area Tuesday and Wednesday. The high will move east on Thursday with the next chance of rain late this weekend. 

.SYNOPSIS...HIGH PRESSURE WILL BRING DRY AND WARMER WEATHER TO
THE AREA TUESDAY AND WEDNESDAY. THE HIGH WILL MOVE EAST ON
THURSDAY WITH THE NEXT CHANCE OF RAIN LATE THIS WEEKEND. [DISC]

Discussion. As of 9:00am PST Tuesday… a 593 dm [decameters] 500 mb high pressure ridge centered just offshore of Baja California will be the dominant syntopic scale feature for our region over the next few days as the ridge apex thrusts into the southern 2/3rds of California. 850 mb temperatures will increase to 17–18°C, while the daily record at 850 mb is within that same range. As a result, temperatures at the surface will also likely rise to within record temperatures for this time of the year. As the ridge is building from south to north, the areas most likely to be meet or beat their records are those farther southward, primarily from the South Bay southward, including most of Monterey, Santa Cruz, and San Benito Counties. Forecast temperatures are within a degree of records in parts of the East Bay as well. Farther north, such as in downtown San Francisco, forecast temperatures are several degrees short of records. 

.DISCUSSION...AS OF 9:00 AM PST TUESDAY... A 593DM 500MB HIGH
PRESSURE RIDGE CENTERED JUST OFFSHORE OF BAJA CALIFORNIA WILL BE
THE DOMINANT SYNTOPIC SCALE FEATURE FOR OUR REGION OVER THE NEXT
FEW DAYS AS THE RIDGE APEX THRUSTS INTO THE SOUTHERN 2/3RDS OF
CALIFORNIA. 850MB TEMPERATURES WILL INCREASE TO 17-18C, WHILE THE
DAILY RECORD AT 850MB IS WITHIN THAT SAME RANGE. AS A RESULT,
TEMPERATURES AT THE SURFACE WILL ALSO LIKELY RISE TO WITHIN RECORD
TEMPERATURES FOR THIS TIME OF THE YEAR. AS THE RIDGE IS BUILDING
FROM SOUTH TO NORTH, THE AREAS MOST LIKELY TO BE MEET OR BEAT
THEIR RECORDS ARE THOSE FARTHER SOUTHWARD, PRIMARILY FROM THE
SOUTH BAY SOUTHWARD, INCLUDING MOST OF MONTEREY, SANTA CRUZ, AND
SAN BENITO COUNTIES. FORECAST TEMPERATURES ARE WITHIN A DEGREE OF
RECORDS IN PARTS OF THE EAST BAY AS WELL. FARTHER NORTH, SUCH AS
IN DOWNTOWN SAN FRANCISCO, FORECAST TEMPERATURES ARE SEVERAL
DEGREES SHORT OF RECORDS. [DISC]

Tomorrow will see similar above average, near record temperatures from the South Bay southward, with a few records again at risk. Models show the ridge weakening on Thanksgiving, with around 2–4° of cooling versus Wednesday. 

TOMORROW WILL SEE SIMILAR ABOVE AVERAGE, NEAR RECORD TEMPERATURES
FROM THE SOUTH BAY SOUTHWARD, WITH A FEW RECORDS AGAIN AT RISK.
MODELS SHOW THE RIDGE WEAKENING ON THANKSGIVING, WITH AROUND 2 TO
4 DEGREES OF COOLING VERSUS WEDNESDAY. [DISC]

Moisture riding over the top of the ridge, a "dirty" ridge pattern, will bring some thin mid to high level cloud coverage through the coming days, especially the farther northward you are located. This moisture will also bring precipitation to extreme Northern California and the Pacific Northwest through the coming days. There is a slight chance that some light precipitation will also fall over northern Napa and Sonoma County as the ridge and an approaching trough push on each other. The next best chance of rain looks to arrive sometime during the weekend. 

MOISTURE RIDING OVER THE TOP OF THE RIDGE, A "DIRTY" RIDGE
PATTERN, WILL BRING SOME THIN MID TO HIGH LEVEL CLOUD COVERAGE
THROUGH THE COMING DAYS, ESPECIALLY THE FARTHER NORTHWARD YOU ARE
LOCATED. THIS MOISTURE WILL ALSO BRING PRECIPITATION TO EXTREME
NORTHERN CALIFORNIA AND THE PACNW THROUGH THE COMING DAYS. THERE
IS A SLIGHT CHANCE THAT SOME LIGHT PRECIPITATION WILL ALSO FALL
OVER NORTHERN NAPA AND SONOMA COUNTY AS THE RIDGE AND AN
APPROACHING TROUGH PUSH ON EACH OTHER. THE NEXT BEST CHANCE OF
RAIN LOOKS TO ARRIVE SOMETIME DURING THE WEEKEND. [DISC]

The current forecast looks on track, so no updates to the overnight forecast are planned this morning. Next forecast update will come early this afternoon. 

THE CURRENT FORECAST LOOKS ON TRACK, SO NO UPDATES TO THE
OVERNIGHT FORECAST ARE PLANNED THIS MORNING. NEXT FORECAST UPDATE
WILL COME EARLY THIS AFTERNOON. [DISC]

Previous discussion… as of 3:00am PST Tuesday. The warm front that brought rain to the North Bay has lifted north as upper level high pressure over Southern California strengthens and builds north. This will lead to a big warmup in temperatures today through Wednesday. Highs will be in the upper 60s and 70s across the SF Bay Area with 70s to lower 80s in the southern part of the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map]. Temperatures on Wednesday will be a couple of degrees warmer than Tuesday and will be the warmest day of the week. We will be under a southwesterly flow so nighttime temperatures will remain quite mild. 

.PREVIOUS DISCUSSION...AS OF 3:00 AM PST TUESDAY...THE WARM FRONT
THAT BROUGHT RAIN TO THE NORTH BAY HAS LIFTED NORTH AS UPPER
LEVEL HIGH PRESSURE OVER SOUTHERN CALIFORNIA STRENGTHENS AND
BUILDS NORTH. THIS WILL LEAD TO A BIG WARMUP IN TEMPERATURES TODAY
THROUGH WEDNESDAY. HIGHS WILL BE IN THE UPPER 60S AND 70S ACROSS
THE SFO BAY AREA WITH 70S TO LOWER 80S IN THE SOUTHERN PART OF THE
CWA. TEMPERATURES ON WEDNESDAY WILL BE A COUPLE OF DEGREES WARMER
THAN TUESDAY AND WILL BE THE WARMEST DAY OF THE WEEK. WE WILL BE
UNDER A SOUTHWESTERLY FLOW SO NIGHTTIME TEMPERATURES WILL REMAIN
QUITE MILD. [DISC]

The ridge will start to flatten on Thursday as an upper level shortwave moves through the Pacific Northwest. Temperatures should cool off slightly and there is a slight chance of rain reaching far northern Sonoma County on Thursday. Partly cloudy but dry conditions are expected for Friday and Saturday as the ridge moves a little further to the east. 

THE RIDGE WILL START TO FLATTEN ON THURSDAY AS AN UPPER LEVEL
SHORTWAVE MOVES THROUGH THE PACIFIC NORTHWEST. TEMPERATURES
SHOULD COOL OFF SLIGHTLY AND THERE IS A SLIGHT CHANCE OF RAIN
REACHING FAR NORTHERN SONOMA COUNTY ON THURSDAY. PARTLY CLOUDY BUT
DRY CONDITIONS ARE EXPECTED FOR FRIDAY AND SATURDAY AS THE RIDGE
MOVES A LITTLE FURTHER TO THE EAST. [DISC]

A weather system will bring a chance of rain to at least the northern part of the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map] on Sunday. This is consistent with 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.] solution while the ECMWF [European Center for Medium-Range Weather Forecasts model] is wetter and brings rain chances to much of the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map]

A WEATHER SYSTEM WILL BRING A CHANCE OF RAIN TO AT LEAST THE
NORTHERN PART OF THE CWA ON SUNDAY. THIS IS CONSISTENT WITH THE
GFS SOLUTION WHILE THE ECMWF IS WETTER AND BRINGS RAIN CHANCES TO
MUCH OF THE CWA. [DISC]

Aviation. As of 09:30am PST Tuesday… for 18Z [10am PST] TAFs [Terminal Aerodrome Forecasts]. Lingering low level moisture has led to some reduced visibility this morning across the North Bay/Santa Clara Valley and East Bay. Expect conditions to slowly improve given the amount of high level clouds overhead. Will primarily forecast VFR [Visual Flight Rules] for most locations with mid-high level clouds. As usual KSTS [Santa Rosa CA] will be problematic with fog possible tonight. Other models hint as some low ceilings tonight, but confidence is low and did not include in TAFs [Terminal Aerodrome Forecasts] 

.AVIATION...AS OF 09:30 AM PST TUESDAY...FOR 18Z TAFS. LINGERING
LOW LEVEL MOISTURE HAS LED TO SOME REDUCED VSBY THIS MORNING
ACROSS THE N BAY/SANTA CLARA VALLEY AND EAST BAY. EXPECT
CONDITIONS TO SLOWLY IMPROVE GIVEN THE AMOUNT OF HIGH LEVEL CLOUDS
OVERHEAD. WILL PRIMARILY FORECAST VFR FOR MOST LOCATIONS WITH
MID-HIGH LEVEL CLOUDS. AS USUAL KSTS WILL BE PROBLEMATIC WITH FOG
POSSIBLE TONIGHT. OTHER MODELS HINT AS SOME LOW CIGS TONIGHT, BUT
CONF IS LOW AND DID NOT INCLUDE IN TAFS [AVIA]

Vicinity of KSFO [San Francisco CA]… mid and high level clouds impacting the Bay. Some haze could impact slant wise, but Don't have much conf on that actually being an impact. VFR [Visual Flight Rules] tonight. Winds light to moderate. 

VICINITY OF KSFO...MID AND HIGH LEVEL CLOUDS IMPACTING THE BAY.
SOME HAZE COULD IMPACT SLANT WISE, BUT DON`T HAVE MUCH CONF ON
THAT ACTUALLY BEING AN IMPACT. VFR TONIGHT. WINDS LIGHT TO
MODERATE. [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]. Confidence is low, but some patch stratus may be around tomorrow am. 

MONTEREY BAY TERMINALS...VFR. CONF IS LOW, BUT SOME PATCH STRATUS
MAY BE AROUND TOMORROW AM. [AVI2]

Marine. As of 09:27am PST Tuesday… light to moderate winds will prevail over the coastal waters with north winds over southern waters and south winds over northern waters. Chances of rain will return to the northern waters towards the end of the week. West to northwest swell will increase mid-week. 

.MARINE...AS OF 09:27 AM PST TUESDAY...LIGHT TO MODERATE WINDS
WILL PREVAIL OVER THE COASTAL WATERS WITH NORTH WINDS OVER
SOUTHERN WATERS AND SOUTH WINDS OVER NORTHERN  WATERS. CHANCES OF
RAIN WILL RETURN TO THE NORTHERN WATERS  TOWARDS THE END OF THE
WEEK. WEST TO NORTHWEST SWELL WILL INCREASE MID-WEEK. [AVIA]

MTR Watches/Warnings/Advisories

  • Today: none. 
.MTR WATCHES/WARNINGS/ADVISORIES...
.TDAY...NONE. [WARN]

Public Forecast: DRP; Aviation: MM; Marine: MM 

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

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Point Forecast

Half Moon Bay Airport

21 Nov 10:50am PST

Today Mostly sunny, with a temperature falling to around 63 by 5pm. East wind around 6 mph becoming WNW in the afternoon.
Tonight Partly cloudy, with a low around 53°. ESE wind 3 to 8 mph.
Wednesday Mostly sunny, with a high near 68°. North wind around 6 mph.
Wednesday Night Partly cloudy, with a low around 53°. NNW wind around 10 mph.
Thanksgiving Day Mostly sunny, with a high near 66°. NNW wind 9 to 14 mph.
Thursday Night Mostly cloudy, with a low around 55°.
Friday Partly sunny, with a high near 65°.
Friday Night Mostly cloudy, with a low around 51°.
Saturday Partly sunny, with a high near 65°.
Saturday Night Mostly cloudy, with a low around 52°.
Sunday Partly sunny, with a high near 63°.
Sunday Night A slight chance of rain. Mostly cloudy, with a low around 50°.
Monday A slight chance of rain. Partly sunny, with a high near 60°.
Today
Mostly sunny, with a temperature falling to around 63 by 5pm. East wind around 6 mph becoming west northwest in the afternoon.
Tonight
Partly cloudy, with a low around 53. East southeast wind 3 to 8 mph.
Wednesday
Mostly sunny, with a high near 68. North wind around 6 mph.
Wednesday Night
Partly cloudy, with a low around 53. North northwest wind around 10 mph.
Thanksgiving Day
Mostly sunny, with a high near 66. North northwest wind 9 to 14 mph.
Thursday Night
Mostly cloudy, with a low around 55.
Friday
Partly sunny, with a high near 65.
Friday Night
Mostly cloudy, with a low around 51.
Saturday
Partly sunny, with a high near 65.
Saturday Night
Mostly cloudy, with a low around 52.
Sunday
Partly sunny, with a high near 63.
Sunday Night
A slight chance of rain. Mostly cloudy, with a low around 50.
Monday
A slight chance of rain. Partly sunny, with a high near 60.

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: