Weather Service Report


115 
FXUS66 KMTR 311202
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
502 AM PDT TUE MAR 31 2015

.SYNOPSIS...A MAINLY DRY COLD FRONT WILL SWEEP ACROSS OUR AREA
TODAY BRINGING MUCH COOLER CONDITIONS THROUGH WEDNESDAY...ALONG
WITH GUSTY WINDS. TEMPERATURES WILL THEN WARM SLIGHTLY BY THE END
OF THE WEEK. DRY WEATHER IS FORECAST AT LEAST THROUGH SATURDAY.
RAIN MAY DEVELOP BY LATE IN THE WEEKEND INTO NEXT WEEK.

&&

.DISCUSSION...AS OF 3:20 AM PDT TUESDAY...AS EXPECTED WINDS HAVE
BEEN LOCALLY BREEZY OVERNIGHT AS A COLD FRONT NEARS OUR CWA.
MODERATE NORTHWESTERLY WINDS OF OVER 40 MPH FOR HIGHER ELEVATION
LOCATIONS WITH GENERALLY 10 TO 20 MPH IN URBAN SPOTS HAVE OCCURRED
FOR MULTIPLE HOURS. WINDS WILL CONTINUE THROUGH THE DAY TODAY AS
THE FRONT GOES ACROSS AND COLD AIR ADVECTION MOVES THROUGH. WOULD
EXPECT A FEW LOCAL PEAKS TO SEE GUSTS AROUND 50 MPH WITH LOWER
ELEVATION SPOTS GENERALLY IN THE TEENS AND 20S. ONE IMPACT OF THE
WINDS HAS BEEN TO MITIGATE THE COOLER AIR RUSHING IN. MOST PLACES
ARE STILL RUNNING NEAR WHERE THEY WERE YESTERDAY.

BREEZY CONDITIONS CAN BE EXPECTED THROUGH AT LEAST WEDNESDAY NIGHT AS
A SYSTEM WILL DIVE DOWN FROM THE NNW INTO NORCAL AND THEN INTO
WESTERN NEVADA. AT THE SAME TIME SURFACE GRADIENTS WILL GREATLY
INCREASES (SFO-LAS APPROACHES 15 MB WHILE SFO-ACV EXCEEDS 6 MB).
MAIN QUESTION REMAINS JUST HOW MUCH OF THE STRONGER WIND WILL MAKE
IT DOWN TO URBAN SPOTS.

AT THE SAME TIME THIS 1-2 PUNCH OF COLDER AIR WILL HELP TO DROP
LOW TEMPERATURES AT ALL SPOTS. HOWEVER...MAIN CONCERN WILL BE FOR
SHELTERED SPOTS FOR POSSIBLE PATCHY FROST. OF PARTICULAR CONCERN
WILL BE NORTH BAY VALLEYS AS ANY FROST COULD CAUSE AGRICULTURAL
PROBLEMS. DECIDED TO GO AGAINST A FROST ADVISORY TONIGHT FOR TWO
REASONS. ONE...OF THE NEARLY 15 DIFFERENT TEMPERATURE SOLUTIONS
LOOKED AT ONLY ONE HAS SPOTS GETTING DOWN TO 35. AND TWO...QUITE
POSSIBLE THAT WINDS WILL STAY UP ENOUGH TO HELP PREVENT LOCATIONS
FROM DROPPING TOO MUCH. DAY CREW WILL WANT TO CLOSELY WATCH THE
LATEST MODEL GUIDANCE TO SEE IF IT STARTS TRENDING COOLER. SIMILAR
CONDITIONS ARE EXPECTED FOR WEDNESDAY MORNING SO THAT WILL NEED TO
BE MONITORED AS WELL.

TEMPERATURES WILL WARM A FEW DEGREES FOR THURSDAY AND FRIDAY AS A
WEAK RIDGE OF HIGH PRESSURE BUILDS BACK INTO OUR AREA. THE RIDGE
WILL FLATTEN OUT ON SATURDAY.

MODELS CONTINUE TO DISAGREE WITH NEXT WEEK WITH THE ECMWF
BRINGING RAIN BACK TO THE REGION ON SUNDAY AS A SYSTEM DROPS DOWN
TO THE NW COAST. GFS REMAINS DRIER AND HAS IT MUCH FARTHER TO THE
NORTH. IT IS WORTH NOTING THAT THE ECMWF IS TRENDING DRIER
COMPARED TO THE PAST COUPLE OF RUNS SUGGESTING THAT THE GFS LINE
OF THOUGHT MAY BE THE WAY TO GO. ONLY MADE VERY MINOR CHANGES TO
THE POPS PAST DAY 5. 
&&

.AVIATION...AS OF 5:00 AM PDT TUESDAY... INFRARED IMAGERY SHOWS
HIGH CLOUDS ASSOCIATED WITH A COLD FRONT BOUNDARY PASSING ALOFT
THIS MORNING. GOES-W SATELLITE DATA SHOWS STRATUS RAPIDLY
DEVELOPING FROM PT REYES ALONG BAY AREA AND NOW SOUTHWARD TOWARDS
THE MONTEREY PENINSULA OVER THE LAST HOUR. STRONG ONSHORE FLOW
QUICKLY USHERED IN AN OVC010 STRATUS DECK THROUGH THE SAN BRUNO
GAP AND INTO THE IMMEDIATE BAY AREA. BUFKIT DATA FROM NAM/RUC/WRF
INDICATE IFR/MVFR CIGS POSBL THROUGH 17-18Z BUT THIS MAY BE
ACCELERATED BY MIXING NEAR THE SFC. BREEZY/GUSTY WINDS ARE
FORECAST TO DEVELOP BY LATE MORNING AND STRENGTHEN INTO THE
AFTERNOON. SUST WINDS 20 TO 30 KT WITH GUSTS 30 TO 40 KT POSBL
THIS AFTERNOON... WITH THE STRONGEST WINDS NEAR KSFO.  

VICINITY OF KSFO...MVFR/IFR CIGS THROUGH 17Z... THEN SCT/FEW
015-020 INTO MIDDAY. AIRPORT WEATHER WARNING ISSUED FOR STRONG
WEST WINDS FROM 21Z TUE TO 03Z WED. GUSTS 30 TO 40 KT POSBL WITH
SUSTAINED WINDS 20 TO 30 KT.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...STRATUS APPROACHING FROM THE
NORTHERN COASTS THIS AM... LIKELY TO SEE DETERIORATING CIGS AS
STRATUS MOVES ONSHORE. MVFR/IFR CIGS THROUGH 18Z POSBL...WITH
LINGER LOW FEW/SCT INTO MIDDAY. WEST WINDS BECOME BREEZY AND
CONTINUE TO STRENGTHEN AFTER 18Z.

&&

.MARINE...AS OF 04:53 AM PDT TUESDAY...MODERATE TO STRONG GUSTY
NORTH TO NORTHWEST WINDS WILL PERSIST THROUGH THE FORECAST PERIOD
ACROSS THE COASTAL WATERS. THE STRONGEST WINDS ARE EXPECTED FROM
POINT SUR AND SOUTHWARD. WINDS MAY OCCASIONALLY GUST INTO GALE
FORCE RANGE. BUILDING MIXED SEAS INTO MIDWEEK. FRESH SWELL AND
SQUARED SEAS MAY LEAD TO LOCALLY HAZARDOUS CONDITIONS.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PT REYES 0-10 NM
             SCA...PT REYES TO PIGEON PT 0-10 NM
             SCA...PIGEON PT TO PT PINOS 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
             GLW...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...ROUGH BAR ADVISORY FOR SF BAR
             SCA...MONTEREY BAY FROM 2 PM
             SCA...SF BAY NORTH OF THE BAY BRIDGE FROM 9 AM
             SCA...SF BAY SOUTH OF THE BAY BRIDGE FROM 9 AM

&&

$$

PUBLIC FORECAST: BELL
AVIATION/MARINE: DRP

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