Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 291218
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
518 AM PDT SUN MAR 29 2015

.SYNOPSIS...MUCH ABOVE NORMAL TEMPERATURES WILL CONTINUE TODAY WITH
RECORD HIGH TEMPERATURES POSSIBLE. A COOLING TREND IS THEN
FORECAST FROM MONDAY THROUGH WEDNESDAY. DRY WEATHER IS EXPECTED TO
PERSIST THROUGH THE FORECAST PERIOD.

&&

.DISCUSSION...AS OF 3:30 AM PDT SUNDAY...CONDITIONS EARLY THIS
MORNING AND SIMILAR TO WHAT THEY WERE 24 HOURS AGO. A STRONG
NORTH-SOUTH SURFACE PRESSURE GRADIENT CONTINUES TO MAINTAIN BRISK
NORTHERLY FLOW OVER THE COASTAL WATERS...WHICH IS KEEPING THE
BOUNDARY LAYER RELATIVELY WELL-MIXED AND FREE OF COASTAL STRATUS.
SURFACE DEWPOINTS ARE GENERALLY RUNNING A FEW DEGREES BELOW WHAT
THEY WERE 24 HOURS AGO...SO IT`S UNLIKELY THERE WILL BE MUCH IN
THE WAY OF COASTAL LOW CLOUD DEVELOPMENT PRIOR TO SUNRISE.
THUS...TODAY SHOULD BE A DAY MUCH LIKE YESTERDAY WITH LOTS OF
SUNSHINE (EXCEPT FOR OCCASIONAL THIN HIGH CLOUDS) AND WARM
TEMPERATURES. EXPECT AFTERNOON HIGHS IN THE MID TO UPPER 60S ALONG
THE IMMEDIATE COAST...WITH 70S TO LOWER 80S ELSEWHERE EXCEPT MID
TO UPPER 80S IN THE WARMEST INLAND VALLEYS. SOME WARM SPOTS LIKE
PINNACLES NATIONAL PARK MAY REACH 90. RECORD HIGH TEMPERATURES ARE
POSSIBLE TODAY.

TODAY WILL BE THE WARMEST DAY OF THE WEEK. AN UPPER TROUGH OVER
THE EASTERN PACIFIC WILL APPROACH THE WEST COAST ON MONDAY. THIS
APPROACHING TROUGH WILL TRIGGER AN INCREASE IN ONSHORE FLOW AND
TEMPERATURES WILL BEGIN TO TREND DOWNWARD ON MONDAY...ALTHOUGH
STILL PROBABLY REMAIN ABOVE NORMAL IN MOST PLACES. THE MODELS
INCREASE LOW LEVEL MOISTURE BY MONDAY EVENING AND WE SHOULD SEE
DEVELOPMENT OF LOW CLOUDS ALONG THE COAST. PRECIPITATION WITH
THIS TROUGH IS FORECAST TO REMAIN WELL TO OUR NORTH.
HOWEVER...STRENGTHENING ONSHORE FLOW ON MONDAY NIGHT COMBINED WITH
INCREASED LOW LEVEL MOISTURE MAY RESULT IN PATCHY DRIZZLE IN
COASTAL AREAS AND ON THE WEST SLOPES OF THE COASTAL HILLS FROM
MONDAY NIGHT INTO TUESDAY MORNING. TEMPERATURES WILL DROP BACK
DOWN TO AROUND NORMAL ON TUESDAY AND LOCALLY BLUSTERY CONDITIONS
ARE EXPECTED NEAR THE COAST AND IN THE HILLS WITH BRISK WEST TO
NORTHWEST WINDS.

A REINFORCING SHOT OF COOL AIR WILL ARRIVE WITH ANOTHER SHORTWAVE
TROUGH ON WEDNESDAY. BUT AT THE SAME TIME SURFACE HIGH PRESSURE
WILL BE BUILDING TO OUR NORTH WHICH WILL INHIBIT ONSHORE FLOW TO
SOME EXTENT AND HALT THE COOLING TREND. SLIGHT WARMING IS THEN
EXPECTED LATE IN THE WEEK AS WEAK UPPER LEVEL RIDGING DEVELOPS.
DRY WEATHER WILL PERSIST THROUGH AT LEAST FRIDAY...AND PROBABLY
INTO SATURDAY AS WELL.

A COLD UPPER TROUGH IN THE GULF OF ALASKA IS FORECAST TO DROP TO
THE SE LATE IN THE WEEK AND POSSIBLY GENERATE PRECIP IN OUR AREA
BY SATURDAY NIGHT AND SUNDAY. BUT THE MEDIUM RANGE MODELS ARE
HAVING A DIFFICULT TIME FORECASTING A CONSISTENT TRAJECTORY FOR
THIS SYSTEM...ALTERNATING BETWEEN A SOLUTION THAT DIGS THE TROUGH
SOUTH ALONG THE COAST (WET) OR ONE THAT SWEEPS IT INLAND TO OUR
NORTH (DRY).

&&

.AVIATION...AS OF 5:00 AM PDT SUNDAY...LATEST FOG PRODUCT SATELLITE
IMAGERY INDICATES MARINE STRATUS NOW DEVELOPING AROUND THE
PERIMETER OF MONTEREY BAY...WITH CIG ONSET HAVING NOW OCCURRED AT
BOTH KMRY AND KSNS. ELSEWHERE SKIES ARE MOSTLY CLEAR. NAM AND
LOCAL HIGH RESOLUTION WRF MODEL OUTPUT BOUNDARY LAYER RELATIVE
HUMIDITIES INDICATE PRETTY CLOSE CALL REGARDING CIG DEVELOPMENT AT
KSFO AND KOAK OVER THE NEXT COUPLE OF HOURS. GIVEN THAT NORTH TO SOUTH
PRESSURE GRADIENT CONTINUES TO BE PRETTY STRONG...AND ABSENCE OF
ANY STRATUS TO THIS POINT IN THE VICINITY OF SF BAY OR ALONG THE
ADJOINING COAST...AM MAINTAINING VFR CONDS AT BOTH THROUGH THE
DAY. CANNOT RULE OUT THE POSSIBILITY THOUGH OF BRIEF CIG DEVELOPMENT.
MUCH HIGHER CONFIDENCE HOWEVER IN VFR CONDITIONS PREVAILING AT ALL
DISTRICT TERMINALS BY LATE MORNING. ONSHORE FLOW THIS AFTERNOON
AND EVENING LOOKS TO BE SIMILAR TO OR JUST A TAD STRONGER THAN ON
SATURDAY.

VICINITY OF KSFO...VFR...BUT CANT RULE OUT POSSIBLE BRIEF CIG
DEVELOPMENT DURING THE FIRST PART OF THE MORNING. AFTERNOON AND
EARLY EVENING SEABREEZE WINDS EXPECTED TO BE SIMILAR TO OR
SLIGHTLY STRONGER THAN ON SATURDAY.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...IFR CIGS HAVE JUST DEVELOPED AT BOTH
KMRY AND KSNS. THESE WILL LIKELY PERSIST THROUGH THE FIRST PART
OF THE MORNING BUT THEN HIGH CONFIDENCE VFR CONDS WILL PREVAIL BY
LATE MORNING.

&&

.MARINE...AS OF 3:57 AM PDT SUNDAY...STRONG AND GUSTY NW WINDS
WILL CONTINUE OVER THE COASTAL WATERS THIS WEEKEND AND NEXT WEEK
AS HIGH PRESSURE REMAINS PARKED OVER THE EASTERN PACIFIC. THE
STRONG WINDS WILL PRODUCE LOCALLY STEEP FRESH SWELLS AND SHORT
PERIOD SEAS.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 3 PM
             SCA...PT ARENA TO PT REYES 0-10 NM
             SCA...PT REYES TO PIGEON PT 0-10 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...PT ARENA TO PT REYES 10-60 NM
             SCA...PT REYES TO PIGEON PT 10-60 NM
             SCA...PIGEON PT TO PT PINOS 10-60 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM

&&

$$

PUBLIC FORECAST: DYKEMA
AVIATION/MARINE: BLIER

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