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

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000
FXUS66 KMTR 011125
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
425 AM PDT SUN MAY 1 2016

.SYNOPSIS....OFFSHORE WINDS WILL CONTINUE TODAY...RESULTING IN
SUNNY AND WARM CONDITIONS IN MOST AREAS. COASTAL FOG AND LOW
CLOUDS WILL LIKELY RETURN BY LATE TODAY OR TONIGHT. SEASONABLE
AND DRY WEATHER IS FORECAST MONDAY AND TUESDAY. A WEATHER SYSTEM
WILL APPROACH CALIFORNIA BY THE MIDDLE OF THE WEEK...BRINGING A
CHANCE OF SHOWERS FROM LATE WEDNESDAY THROUGH THE END OF THE
WEEK...ALONG WITH COOLER THAN NORMAL TEMPERATURES.

&&

.DISCUSSION...AS OF 3:25 AM PDT SUNDAY...SKIES ARE CLEAR ACROSS
OUR ENTIRE FORECAST AREA EARLY THIS MORNING AS LIGHT OFFSHORE FLOW
CONTINUES. CURRENT TEMPERATURES ARE GENERALLY WARMER THAN 24 HOURS
AGO AND IN SOME CASES SEVERAL DEGREES WARMER. FORECAST GUIDANCE
INDICATES HIGH TEMPERATURES TODAY WILL BE ABOUT FIVE DEGREES
WARMER THAN YESTERDAY. HOWEVER...MODELS FORECAST AN END TO
OFFSHORE FLOW TODAY ALONG WITH THE DEVELOPMENT OF SOUTHERLY FLOW
ALONG THE COAST. THIS DOES NOT LOOK LIKE A CLASSIC "SOUTHERLY
SURGE" SCENARIO...SINCE LOW CLOUDS DO NOT ALREADY EXIST TO OUR
SOUTH NEAR POINT CONCEPTION. WHAT`S MORE LIKELY TO HAPPEN IS THAT
LOW CLOUDS AND FOG WILL FORM IN COASTAL AREAS FROM MONTEREY BAY
SOUTH BY EARLY AFTERNOON...AND THEN MOVE NORTH UP ALONG THE REST
OF OUR COAST LATE THIS AFTERNOON AND EVENING. THIS MAKES FOR A
DIFFICULT TEMPERATURE FORECAST TODAY FOR COASTAL AREAS SINCE THE
TIMING OF THE SOUTHERLY WIND ONSET AND COASTAL FOG DEVELOPMENT
WILL HAVE A BIG IMPACT ON TEMPERATURES. MOST LIKELY SCENARIO IS
FOR COOLING TO OCCUR IN LOCATIONS LIKE BIG SUR AND SANTA CRUZ
WHILE OTHER COASTAL AREAS WILL BE AS WARM OR WARMER THAN
YESTERDAY.

ANOTHER ITEM TO WATCH TODAY IS A SHORTWAVE TROUGH CURRENTLY OVER
SOUTHEAST OREGON THAT IS ROTATING AROUND A LONGWAVE TROUGH
CENTERED OVER THE DESERT SW. THIS SHORTWAVE IS FORECAST TO ROTATE
INTO NORTHERN AND CENTRAL CALIFORNIA LATER TODAY. THE ECMWF KEEPS
ALL PRECIP ASSOCIATED WITH THIS SHORTWAVE TO OUR EAST...MAINLY OVER
THE SIERRA NEVADA. HOWEVER...BOTH THE 00Z NAM AND 00Z GFS
FORECAST ISOLATED SHOWERS ALONG THE EASTERN FRINGES OF OUR
FORECAST AREA LATE THIS AFTERNOON AND EARLY THIS EVENING. HAVE
THEREFORE ADDED SLIGHT CHANCE POPS TO FAR EASTERN ALAMEDA...SANTA
CLARA...AND SAN BENITO COUNTIES FOR LATER TODAY.

DRY AND MILD WEATHER IS FORECAST FOR MONDAY AND TUESDAY. ONSHORE
FLOW WILL LIKELY MAINTAIN AT LEAST AREAS OF NIGHT AND MORNING LOW
CLOUDS AND TEMPERATURES WILL BE NEAR NORMAL.

AN UPPER TROUGH CURRENTLY SEEN ON SATELLITE IMAGERY OFFSHORE ALONG
145W IS FORECAST TO GRADUALLY APPROACH THE CALIFORNIA COAST OVER
THE NEXT THREE DAYS AND BEGIN TO GENERATE SHOWER CHANCES ACROSS
OUR AREA BY LATE WEDNESDAY. BOTH THE GFS AND ECMWF FORECAST A
CUTOFF LOW TO DEVELOP NEAR SAN FRANCISCO BY THURSDAY...WITH THAT
LOW THEN PROJECTED TO DROP SOUTHEAST AND TRACK ACROSS SOUTHERN
CALIFORNIA BY LATE FRIDAY AND FRIDAY NIGHT. THUS...SHOWER CHANCES
WILL CONTINUE THROUGH THE END OF THE WEEK AND PROBABLY INTO NEXT
WEEKEND AS WELL. GIVEN THE UNPREDICTABILITY OF CUTOFF LOW
MOVEMENT...IT`S DIFFICULT TO PINPOINT WHERE SHOWER CHANCES WILL BE
GREATEST DURING THE SECOND HALF OF THE WEEK. ISOLATED THUNDERSTORMS
MAY ALSO OCCUR...BUT WILL WAIT TO ADD THUNDERSTORMS TO THE
FORECAST UNTIL CONFIDENCE INCREASES ON THE TIMING AND TRACK OF THE
UPPER LOW. IN ADDITION TO PRECIPITATION CHANCES...THIS UPPER LOW
WILL RESULT IN COOLER THAN NORMAL CONDITIONS ACROSS MOST OF OUR
AREA DURING THE SECOND HALF OF THE WEEK.

&&

.AVIATION...AS OF 4:21 AM PDT SUNDAY...DRY OFFSHORE FLOW KEEPING
MAINLY VFR TODAY. THE ONE FLY IN THE OINTMENT IN THE FORECAST
IS A POSSIBLE SOUTHERLY SURGE LATER TODAY. LATEST NAM AND WRF SHOW
A SOUTHERLY SURGE IMPACTING KMRY/KSNS...POSS MAKING IT INTO SF BAY
OVERNIGHT. CONF IS MARGINAL...BUT WILL ADD CIGS TO MONTEREY BAY.

VICINITY OF KSFO...VFR.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY TERMINALS...VFR WITH SOME HAZE IN THE AM. VFR
BECOMING MVFR THIS EVENING AND OVERNIGHT..

&&

.MARINE...AS OF 04:19 AM PDT SUNDAY...BUILDING HIGH PRESSURE OVER
THE EASTERN PACIFIC WILL KEEP NORTHERLY WINDS OVER THE COASTAL
WATERS TODAY. LOCALLY GUSTY WINDS WILL BE POSSIBLE OVER THE OUTER
WATERS NORTH OF POINT REYES. SOUTHERLY WINDS WILL DEVELOP LATE
TONIGHT AND EARLY MONDAY. A MODERATE SWELL WILL MIX WITH A SMALLER
LONG PERIOD SOUTHERLY SWELL THIS WEEK.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM UNTIL 9 AM

&&

$$

PUBLIC FORECAST: DYKEMA
AVIATION: MM
MARINE: MM


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