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Area Forecast Discussion

FXUS66 KMTR [Monterey CA] 180535 AFDMTR 

FXUS66 KMTR 180535
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 10:35pm PDT Thu Aug 17 2017 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1035 PM PDT THU AUG 17 2017 [HEAD]

Synopsis. A gradual warming trend is forecast to continue through late week as high pressure builds over the region. With this, overnight and morning clouds can be expected as well, especially along the coast and nearby valley locations. A cooling trend is then expected late in the weekend into early next week as an upper level trough impacts the region. 

.SYNOPSIS...A GRADUAL WARMING TREND IS FORECAST TO CONTINUE
THROUGH LATE WEEK AS HIGH PRESSURE BUILDS OVER THE REGION. WITH
THIS, OVERNIGHT AND MORNING CLOUDS CAN BE EXPECTED AS WELL,
ESPECIALLY ALONG THE COAST AND NEARBY VALLEY LOCATIONS. A COOLING
TREND IS THEN EXPECTED LATE IN THE WEEKEND INTO EARLY NEXT WEEK AS
AN UPPER LEVEL TROUGH IMPACTS THE REGION. [DISC]

Discussion. As of 8:57pm PDT Thursday… mostly clear skies prevail this evening with low clouds currently only impacting the north coast of the forecast area. Low clouds are sliding in through coastal gaps and valley over Marin and Sonoma Counties under a compressing 1400 ft marine layer. Low clouds are anticipated to fill in along the coast overnight however low clouds will not be as extensive as previous mornings as a result of a ridge of high pressure building over the eastern Pacific that is consequently compressing the marine layer along the coast. 

.DISCUSSION...AS OF 8:57 PM PDT THURSDAY...MOSTLY CLEAR SKIES
PREVAIL THIS EVENING WITH LOW CLOUDS CURRENTLY ONLY IMPACTING THE
NORTH COAST OF THE FORECAST AREA. LOW CLOUDS ARE SLIDING IN
THROUGH COASTAL GAPS AND VALLEY OVER MARIN AND SONOMA COUNTIES UNDER
A COMPRESSING 1400 FT MARINE LAYER. LOW CLOUDS ARE ANTICIPATED TO
FILL IN ALONG THE COAST OVERNIGHT HOWEVER LOW CLOUDS WILL NOT BE
AS EXTENSIVE AS PREVIOUS MORNINGS AS A RESULT OF A RIDGE OF HIGH
PRESSURE BUILDING OVER THE EASTERN PACIFIC THAT IS CONSEQUENTLY
COMPRESSING THE MARINE LAYER ALONG THE COAST. [DISC]

Temperatures finished of the day significantly warmer then yesterday as the warming trend continued across the district. Temperatures Rose 2–3° along the coast to an average of 7° inland. Highs reached into the mid to upper 60s along the coast, 70s around the bays and mid 70s and 80s inland. The warmest inland valley locations topped out in the upper 80s to around 90°. Bradley was our hot spot today with a high of 90°. The warming trend will continue one more day and peak on Friday. 

TEMPERATURES FINISHED OF THE DAY SIGNIFICANTLY WARMER THEN
YESTERDAY AS THE WARMING TREND CONTINUED ACROSS THE DISTRICT.
TEMPERATURES ROSE 2-3 DEGREES ALONG THE COAST TO AN AVERAGE OF 7
DEGREES INLAND. HIGHS REACHED INTO THE MID TO UPPER 60S ALONG THE
COAST, 70S AROUND THE BAYS AND MID 70S AND 80S INLAND. THE
WARMEST INLAND VALLEY LOCATIONS TOPPED OUT IN THE UPPER 80S TO
AROUND 90 DEGREES. BRADLEY WAS OUR HOT SPOT TODAY WITH A HIGH OF
90 DEGREES. THE WARMING TREND WILL CONTINUE ONE MORE DAY AND PEAK
ON FRIDAY. [DISC]

Tonight low will be similar to last night in most locations while slightly warmer overnight lows are anticipated across elevated terrain situated above the marine inversion. The Fort Ord profiler [instrument designed to measure horizontal winds directly above its location, and thus measure the vertical wind profile. Profilers operate on the same principles as Doppler radar.] nicely depict the warming aloft as high pressure builds across the region. It also depicts a shallower marine layer that will hamper the spread of low clouds overnight. Therefore anticipate less stratus coverage and hence a slightly quicker burnoff Friday morning. Low clouds will give way to mostly sunny skies in the afternoon for most locations on Friday and Saturday with afternoon highs near seasonal averages with 60s to 70s at the coast and 80s to 90s inland. 

TONIGHT LOW WILL BE SIMILAR TO LAST NIGHT IN MOST LOCATIONS WHILE
SLIGHTLY WARMER OVERNIGHT LOWS ARE ANTICIPATED ACROSS ELEVATED
TERRAIN SITUATED ABOVE THE MARINE INVERSION. THE FORT ORD PROFILER
NICELY DEPICT THE WARMING ALOFT AS HIGH PRESSURE BUILDS ACROSS THE
REGION. IT ALSO DEPICTS A SHALLOWER MARINE LAYER THAT WILL HAMPER
THE SPREAD OF LOW CLOUDS OVERNIGHT. THEREFORE ANTICIPATE LESS
STRATUS COVERAGE AND HENCE A SLIGHTLY QUICKER BURNOFF FRIDAY
MORNING. LOW CLOUDS WILL GIVE WAY TO MOSTLY SUNNY SKIES IN THE
AFTERNOON FOR MOST LOCATIONS ON FRIDAY AND SATURDAY WITH AFTERNOON
HIGHS NEAR SEASONAL AVERAGES WITH 60S TO 70S AT THE COAST AND 80S
TO 90S INLAND. [DISC]

From previous discussion. The aforementioned ridge of high pressure will shift westward out further into the Pacific this upcoming weekend and be replaced by a mid/upper level trough. The latest model run of 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.] continues to maintain near average temperatures on Saturday before showing a cooling trend spreading inland Sunday. Meanwhile, the NAM [North American Meso (formerly Eta) model] and ECMWF [European Center for Medium-Range Weather Forecasts model] both show the cooling trend to begin on Saturday and spreading inland into early next week. Regardless, temperatures are forecast to cool slightly below seasonal averages early next week. The challenging part of the forecast will be how much this mid/upper level trough and associated low that is forecast to develop will impact the marine layer. Depending on the exact set up, the marine layer may mix out early in the week and result in earlier than normal burn-off time of low clouds. Overall, dry weather conditions are also forecast to persist through the middle of next week. 

FROM PREVIOUS DISCUSSION...THE AFOREMENTIONED RIDGE OF HIGH
PRESSURE WILL SHIFT WESTWARD OUT FURTHER INTO THE PACIFIC THIS
UPCOMING WEEKEND AND BE REPLACED BY A MID/UPPER LEVEL TROUGH. THE
LATEST MODEL RUN OF THE GFS CONTINUES TO MAINTAIN NEAR AVERAGE
TEMPERATURES ON SATURDAY BEFORE SHOWING A COOLING TREND SPREADING
INLAND SUNDAY. MEANWHILE, THE NAM AND ECMWF BOTH SHOW THE COOLING
TREND TO BEGIN ON SATURDAY AND SPREADING INLAND INTO EARLY NEXT
WEEK. REGARDLESS, TEMPERATURES ARE FORECAST TO COOL SLIGHTLY BELOW
SEASONAL AVERAGES EARLY NEXT WEEK. THE CHALLENGING PART OF THE
FORECAST WILL BE HOW MUCH THIS MID/UPPER LEVEL TROUGH AND
ASSOCIATED LOW THAT IS FORECAST TO DEVELOP WILL IMPACT THE MARINE
LAYER. DEPENDING ON THE EXACT SET UP, THE MARINE LAYER MAY MIX OUT
EARLY IN THE WEEK AND RESULT IN EARLIER THAN NORMAL BURN-OFF TIME
OF LOW CLOUDS. OVERALL, DRY WEATHER CONDITIONS ARE ALSO FORECAST
TO PERSIST THROUGH THE MIDDLE OF NEXT WEEK. [DISC]

Aviation. As of 10:30pm PDT Thursday… onshore gradients have become more east-west this evening and stratus is starting to spread into the northern SF Bay Area and the North Bay. Ceilings are expected into SFO [San Francisco CA] OAK [Oakland CA] and STS [Santa Rosa CA] tonight but a southeast wind should keep it out of SJC [San Jose CA]. The marine layer is expected to compress further overnight and will lead to earlier clearing on Friday. 

.AVIATION...AS OF 10:30 PM PDT THURSDAY...ONSHORE GRADIENTS HAVE
BECOME MORE EAST-WEST THIS EVENING AND STRATUS IS STARTING TO
SPREAD INTO THE NORTHERN SFO BAY AREA AND THE NORTH BAY. CIGS ARE
EXPECTED INTO SFO OAK AND STS TONIGHT BUT A SOUTHEAST WIND SHOULD
KEEP IT OUT OF SJC. THE MARINE LAYER IS EXPECTED TO COMPRESS
FURTHER OVERNIGHT AND WILL LEAD TO EARLIER CLEARING ON FRIDAY. [AVIA]

Vicinity of KSFO [San Francisco CA]MVFR [Marginal Visual Flight Rules] after 10Z [3am PDT]

VICINITY OF KSFO...MVFR AFTER 10Z. [AVI2]

SFO [San Francisco CA] bridge approach… similar to KSFO [San Francisco CA]

SFO BRIDGE APPROACH...SIMILAR TO KSFO. [AVI2]

Monterey Bay terminals… stratus has remained well offshore through the early evening hours. In the past this usually meant the Monterey Bay Area would remain clear all night. Ceilings have been removed from the latest TAFs [Terminal Aerodrome Forecasts]

MONTEREY BAY TERMINALS...STRATUS HAS REMAINED WELL OFFSHORE
THROUGH THE EARLY EVENING HOURS. IN THE PAST THIS USUALLY MEANT
THE MRY BAY AREA WOULD REMAIN CLEAR ALL NIGHT. CIGS HAVE BEEN
REMOVED FROM THE LATEST TAFS. [AVI2]

Marine. As of 10:30pm PDT Thursday… a 1027 mb high is centered 750 miles west of Cape Mendocino. A ridge will build from this high into the Pacific Northwest this weekend. This will result in increasing northwest windsover the northern waters. 

.MARINE...AS OF 10:30 PM PDT THURSDAY...A 1027 MB HIGH IS
CENTERED 750 MILES WEST OF CAPE MENDOCINO. A RIDGE WILL BUILD FROM
THIS HIGH INTO THE PACIFIC NORTHWEST THIS WEEKEND. THIS WILL
RESULT IN INCREASING NORTHWEST WINDSOVER THE NORTHERN WATERS. [AVIA]

MTR Watches/Warnings/Advisories

  • Tonight: none. 
.MTR WATCHES/WARNINGS/ADVISORIES...
.TNGT...NONE. [WARN]

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

PUBLIC FORECAST: CW
AVIATION: W PI
MARINE: W PI [CRED]
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Point Forecast

Half Moon Bay CA

17 Aug 11:15pm PDT

Tonight Patchy fog. Otherwise, mostly cloudy, with a low around 56°. SW wind around 6 mph.
Friday Patchy fog before 11am. Otherwise, mostly cloudy, then gradually becoming sunny, with a high near 68°. SW wind 6 to 11 mph.
Friday Night Patchy fog after 11pm. Otherwise, increasing clouds, with a low around 56°. SW wind 5 to 10 mph.
Saturday Patchy fog before 11am. Otherwise, mostly cloudy, then gradually becoming sunny, with a high near 67°. SW wind 8 to 11 mph.
Saturday Night Patchy fog after 11pm. Otherwise, partly cloudy, with a low around 55°. SW wind around 11 mph.
Sunday Patchy fog before 11am. Otherwise, mostly sunny, with a high near 67°.
Sunday Night Patchy fog after 11pm. Otherwise, partly cloudy, with a low around 56°.
Monday Patchy fog before 11am. Otherwise, mostly sunny, with a high near 67°.
Monday Night Mostly cloudy, with a low around 57°.
Tuesday Mostly sunny, with a high near 67°.
Tuesday Night Partly cloudy, with a low around 55°.
Wednesday Mostly sunny, with a high near 66°.
Wednesday Night Mostly clear, with a low around 55°.
Thursday Sunny, with a high near 67°.
Tonight
Patchy fog. Otherwise, mostly cloudy, with a low around 56. Southwest wind around 6 mph.
Friday
Patchy fog before 11am. Otherwise, mostly cloudy, then gradually becoming sunny, with a high near 68. Southwest wind 6 to 11 mph.
Friday Night
Patchy fog after 11pm. Otherwise, increasing clouds, with a low around 56. Southwest wind 5 to 10 mph.
Saturday
Patchy fog before 11am. Otherwise, mostly cloudy, then gradually becoming sunny, with a high near 67. Southwest wind 8 to 11 mph.
Saturday Night
Patchy fog after 11pm. Otherwise, partly cloudy, with a low around 55. Southwest wind around 11 mph.
Sunday
Patchy fog before 11am. Otherwise, mostly sunny, with a high near 67.
Sunday Night
Patchy fog after 11pm. Otherwise, partly cloudy, with a low around 56.
Monday
Patchy fog before 11am. Otherwise, mostly sunny, with a high near 67.
Monday Night
Mostly cloudy, with a low around 57.
Tuesday
Mostly sunny, with a high near 67.
Tuesday Night
Partly cloudy, with a low around 55.
Wednesday
Mostly sunny, with a high near 66.
Wednesday Night
Mostly clear, with a low around 55.
Thursday
Sunny, with a high near 67.

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: