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

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000
FXUS66 KMTR 180548
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1048 PM PDT FRI APR 17 2015

.SYNOPSIS...HIGH PRESSURE THIS WEEKEND WILL BRING SEASONABLE
TEMPERATURES WITH TRANQUIL CONDITIONS. BY MONDAY SOME INSTABILITY
WILL DEVELOP OVER THE REGION...PRODUCING CUMULUS CLOUDS AND A
SLIGHT CHANCE OF AN ISOLATED SHOWER OR THUNDERSTORM ACROSS SOME OF
THE REMOTE INTERIOR HILLS. BY TUESDAY AND WEDNESDAY AN UPPER LOW
WILL APPROACH...RESULTING IN A COOLING TREND ALONG WITH A SLIGHT
CHANCE OF SHOWERS...MAINLY OVER THE HILLS.

&&

.DISCUSSION...AS OF 8:40 PM PDT FRIDAY...A SHALLOW MARINE LAYER
DEVELOPED TODAY...RESULTING IN UP TO TEN DEGREES OF COOLING NEAR
THE IMMEDIATE COAST...MAINLY FROM SAN MATEO COUNTY NORTHWARD. BUT
MOST AREAS AWAY FROM THE COAST REMAINED ISOLATED FROM THE COOLING
EFFECTS OF THE SHALLOW MARINE LAYER AND LIGHT ONSHORE FLOW AND
ENDED UP BEING AS WARM AS YESTERDAY...OR EVEN A BIT WARMER. A
RECORD HIGH OF 86 OCCURRED IN SANTA CRUZ TODAY AND SALINAS TIED
THEIR RECORD HIGH FOR THE DAY WITH AN 81.

A WEAK SHORTWAVE TROUGH IS CURRENTLY MOVING INLAND ACROSS THE PAC
NW. THIS WEAK UPPER LEVEL DISTURBANCE IS FORECAST TO DROP SOUTH
INTO NORTHERN CA ON SATURDAY AND THEN FORM A WEAK CUTOFF LOW OFF
THE NORTHERN CA COAST BY LATE SUNDAY. THIS SYSTEM IS EXPECTED TO BE
TOO WEAK AND DRY TO GENERATE ANY PRECIP OVER OUR AREA THROUGH THE
WEEKEND...BUT IT WILL LIKELY RESULT IN AN INCREASE IN THE DEPTH
OF THE MARINE LAYER AND THUS AT LEAST SLIGHT COOLING OVER THE
NEXT TWO DAYS. ONSHORE FLOW IS FORECAST TO REMAIN WEAK THROUGH THE
WEEKEND AND SO INLAND AREAS WILL PROBABLY SEE ONLY MODEST COOLING.
THE UPSHOT IS THAT COASTAL AREAS CAN EXPECT AREAS OF LOW CLOUDS
AND FOG THIS WEEKEND...BUT INLAND AREAS SHOULD REMAIN MOSTLY
CLEAR AND WARM. BY MONDAY ONSHORE FLOW IS EXPECTED TO INCREASE
WHICH WILL BE THE START OF A REGION-WIDE COOLING TREND. IN
ADDITION...MOISTURE IS FORECAST TO INCREASE SOMEWHAT ACROSS THE
SOUTHERN PART OF OUR FORECAST AREA ON MONDAY AND THERE MAY BE JUST
ENOUGH INSTABILITY OVER THE HIGHER HILLS BY THAT AFTERNOON TO
GENERATE ISOLATED SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF
SOUTHERN SAN BENITO COUNTY.

THE COOLING TREND IS EXPECTED TO RAMP UP ON TUESDAY AS AN UPPER
TROUGH APPROACHES FROM THE NW. THAT TROUGH IS THEN FORECAST TO DIG
SOUTH ALONG THE CA COAST ON TUESDAY NIGHT AND WEDNESDAY...FORMING
AN UPPER LOW NEAR THE CENTRAL CA COAST BY LATE WEDNESDAY. SHOWER
CHANCES WILL SPREAD FROM NORTH TO SOUTH ACROSS OUR REGION FROM
TUESDAY INTO WEDNESDAY...BUT THE MEDIUM RANGE MODELS AGREE THAT
THE BULK OF THE PRECIPITATION WITH THIS MIDWEEK SYSTEM WILL FALL
OVER THE HIGHER MOUNTAINS OF CA (E.G., SIERRA NEVADA).

THE PATTERN IS FORECAST TO REMAIN UNSETTLED INTO LATE NEXT
WEEK...BUT THE LIKELIHOOD OF RAINFALL OF ANY SIGNIFICANCE IS
DIFFICULT TO PREDICT AT THIS POINT GIVEN MODEL DIFFERENCES. THE
12Z ECMWF OFFERS THE BEST HOPE OF WIDESPREAD RAINFALL...SHOWING A
POTENT AND RELATIVELY WET LITTLE SYSTEM SWEEPING ACROSS CENTRAL CA
FROM LATE NEXT FRIDAY THROUGH SATURDAY MORNING.

&&

.AVIATION...AS OF 10:50 PM PDT FRIDAY...THE CURRENT IR SATELLITE
FOG PRODUCT IS SHOWING STRATUS MOVING IN ALONG THE CENTRAL
CALIFORNIA COAST THIS EVENING PUSHING INTO PORTIONS OF THE SAN
FRANCISCO BAY AND MONTEREY BAY. THE FORT ORD PROFILER CONTINUES TO
SHOW A MARINE LAYER APPROXIMATELY 800 FEET DEEP. WITH SUFFICIENT
ONSHORE FLOW THE SHALLOW MARINE LAYER WILL CONTINUE TO ADVECT INTO
THE SAN FRANCISCO BAY AREA RESULTING IN LOW CIGS OVERNIGHT. THE
WRF HIGH RES FORECAST MODEL DEVELOPS AN EDDY IN MONTEREY BAY WHICH
MAY KEEP STRATUS OUT OF THE MONTEREY BAY AREA TERMINALS OVERNIGHT.

VICINITY OF KSFO...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH
AROUND 1200Z AT WHICH POINT BKN-OVC008 WILL BE POSSIBLE. FIRST
GUESS AT THE MORNING BURN OFF IS 1700Z.

CONFIDENCE IS MODERATE.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR IS EXPECTED TO PREVAIL THROUGH
THE NEXT 24 HOURS. HOWEVER...A PERIOD OF LOW CIGS BKN-OVC008 WILL
BE POSSIBLE AFTER MIDNIGHT.

CONFIDENCE IS MODERATE.

&&

.CLIMATE...RECORD HIGH TEMPERATURES FOR FRIDAY (4/17)
ALONG WITH THE MOST RECENT DATE IT OCCURRED.

SF BAY AREA
.LOCATION.................4/17
 KENTFIELD...............89/1999
 SAN RAFAEL..............88/1954
 NAPA....................88/1954
 SAN FRANCISCO...........79/1954
 SFO AIRPORT.............82/1954
 OAKLAND (DOWNTOWN)......78/1977
 OAKLAND AIRPORT.........87/1954
 RICHMOND................86/1954
 LIVERMORE...............90/1966
 MOFFETT FIELD...........83/1954
 SAN JOSE................92/1999
 GILROY..................92/1999

MONTEREY BAY AREA
.LOCATION.................4/17
 MONTEREY................80/1952
 SANTA CRUZ..............84/1938
 SALINAS.................81/1999
 SALINAS AIRPORT.........87/1952
 KING CITY...............98/1954

&&

.MARINE...AS OF 10:42 PM PDT FRIDAY...A BROAD THERMAL TROUGH
POSITIONED OVER MUCH OF CALIFORNIA WILL MAINTAIN GENERALLY LIGHT
TO MODERATE WESTERLY WINDS THROUGH THE BEGINNING OF THE WORK WEEK.
WINDS WILL BE LOCALLY STRONGER NORTH OF POINT REYES...ESPECIALLY
OVER THE OUTER WATERS. NORTHERLY WINDS WILL INCREASE ONCE AGAIN
ACROSS THE COASTAL WATERS BY MID WEEK. SEAS ARE EXPECTED TO
DECREASE OVERNIGHT AS GENTLER SEAS MOVE IN FOR THE REMAINDER OF
THE WEEKEND.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PT ARENA TO PT REYES 10-60 NM
             SCA...ROUGH BAR ADVISORY FOR SF BAR UNTIL 6 AM

&&

$$

PUBLIC FORECAST: DYKEMA
AVIATION/MARINE: LARRY
CLIMATE: HENDERSON/BELL

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