Weather Service Report


973 
FXUS66 KMTR 280357
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
857 PM PDT WED MAY 27 2015

.SYNOPSIS...HIGH PRESSURE BUILDING ALONG THE WEST COAST WILL
RESULT IN A MODEST WARMING TREND THROUGH SATURDAY...MOST APPARENT
INLAND. TEMPERATURES WILL THEN COOL SUNDAY INTO EARLY NEXT WEEK
AS A WEAK UPPER LEVEL TROUGH APPROACHES THE COAST. THERE IS A SLIGHT
CHANCE OF SHOWERS ACROSS THE NORTH BAY FROM LATE SUNDAY INTO
MONDAY...BUT MOST LOCATIONS ARE EXPECTED TO REMAIN DRY THROUGH THE
FORECAST PERIOD.

&&

.DISCUSSION...AS OF 8:55 PM PDT WEDNESDAY...ALTHOUGH THE MARINE
LAYER COMPRESSED SLIGHTLY TODAY AS THE UPPER RIDGE OFFSHORE EDGED
CLOSER TO THE COAST...IT HAS HELD RELATIVELY DEEP AT 2000
FEET. AND...ONSHORE SURFACE PRESSURE GRADIENTS HAVE REMAINED
RELATIVELY ROBUST. CONSEQUENTLY...TEMPERATURES TODAY WERE BELOW
NORMAL YET AGAIN...A TREND THAT HAS CONTINUED UNABATED FOR NEARLY
THE ENTIRE MONTH OF MAY.

EVENING WATER VAPOR SATELLITE IMAGERY SHOWS THE UPPER RIDGE JUST
OFFSHORE...CENTERED ALONG 128W...MOVING SLOWLY TO THE EAST. THE
MODELS CONTINUE TO SHOW THE RIDGE SHIFTING EASTWARD OVER CA OVER THE
NEXT TWO DAYS AND ALSO AMPLIFYING A BIT. INLAND AREAS SHOULD SEE
TEMPERATURES FINALLY CLIMB TO NEAR NORMAL TOMORROW AND THEN ABOVE
NORMAL BY FRIDAY AND SATURDAY. MEANWHILE...A STUBBORN ONSHORE FLOW
WILL PREVENT COASTAL AREAS FROM WARMING MUCH. THE MARINE LAYER
WILL LIKELY COMPRESS TO ABOUT 1000 FEET BY WEEK'S END...WHICH WILL
LIMIT THE AMOUNT OF NIGHT AND MORNING LOW CLOUDS ACROSS INLAND
AREAS...AND ALSO ALLOW FOR MORE AFTERNOON CLEARING NEAR THE OCEAN.
BUT SOME COASTAL SPOTS WILL LIKELY REMAIN MIRED IN LOW CLOUDS AND
FOG THROUGH THE END OF THE WEEK AND INTO THE WEEKEND. WITH A
COMPRESSED MARINE LAYER...FOG WILL BECOME MORE OF AN ISSUE IN
COASTAL AREAS AND WE WILL LIKELY SEE SOME PATCHY DENSE FOG NEAR
THE OCEAN BY WEEK'S END.

THE RIDGE IS FORECAST TO GRADUALLY MOVE OFF TO OUR EAST OVER THE
WEEKEND. SATURDAY WILL BE THE FINAL WARM DAY FOR INLAND AREAS BEFORE
AN APPROACHING UPPER TROUGH TRIGGERS A RAPID DEEPENING IN THE
MARINE LAYER BY SATURDAY NIGHT AND A STRONG INLAND PUSH OF MARINE
AIR AND ASSOCIATED COOLING BY SUNDAY. IN ADDITION...MOST MODELS
INDICATE THIS WEATHER SYSTEM MAY PRODUCE SOME LIGHT RAIN ACROSS
THE NORTHERN PART OF OUR FORECAST AREA FROM LATE SUNDAY AFTERNOON
THROUGH SUNDAY NIGHT. THE 12Z ECMWF IS THE MOST BULLISH WITH
PRECIP...AND ALSO FASTEST...DROPPING MEASURABLE RAIN AS FAR SOUTH
AS SAN MATEO COUNTY BY LATE SUNDAY AFTERNOON. DEPENDING ON WHAT
THE 00Z MODELS SHOW...WE MAY NEED TO INCREASE POPS ACROSS THE
NORTH BAY ON SUNDAY AFTERNOON AND SUNDAY NIGHT...AND ALSO EXTEND
POPS A BIT FARTHER SOUTH. THE INCOMING TROUGH WILL ALSO LIKELY
GENERATE COASTAL DRIZZLE ALONG OUR ENTIRE COAST ON SATURDAY NIGHT
AND SUNDAY. INLAND TEMPERATURES ARE EXPECTED TO COOL BY AS MUCH
AS TEN DEGREES FROM SATURDAY INTO SUNDAY AND THEN ANOTHER 5-10
DEGREES BY MONDAY.

&&

.AVIATION...AS OF 4:39 PM PDT WEDNESDAY...COASTAL LOW CLOUDS WILL
BE USHERED INLAND BY ONSHORE WINDS AGAIN TONIGHT. THE MARINE LAYER
HAS COMPRESSED A LITTLE SINCE LAST EVENING AND IS ROUGHLY 2500
FEET DEEP. THE UPPER LEVEL RIDGE OVER THE AREA WILL GRADUALLY
STRENGTHEN DURING THE PERIOD.

VICINITY OF KSFO...EARLY STRATUS ARRIVAL AT KSFO WITH MVFR CIG
REPORTED SINCE 2240Z. CONTINUED STRATUS FEED FAVORED BY WESTERLY
WINDS AND A MODERATELY DEEP MARINE LAYER.

KSFO BRIDGE APPROACH...PER COORD WITH OAKLAND CWSU THOUGHT IS THAT
THE STRATUS WILL REACH THE APPROACH BY APPROX 04Z-05Z. CLEARING
EXPECTED BY LATE THURSDAY MORNING.
 
MONTEREY BAY AREA TERMINALS...MVFR CIGS DEVELOPING BETWEEN 00Z-04Z
FOLLOWED BY MVFR CIGS OVERNIGHT. CLEARING IS LIKELY BY LATE
MORNING THURSDAY.

&&

.MARINE...AS OF 02:39 PM PDT WEDNESDAY...HIGH PRESSURE OVER THE
CENTRAL COAST WILL LEAD TO LIGHT NORTHWEST WINDS AND GENTLE SEAS
THIS AFTERNOON. NORTHWEST WINDS ARE FORECAST TO BEGIN TO INCREASE
TONIGHT WITH THE STRONGEST WINDS ALONG THE BIG SUR COASTLINE
THROUGH THE REMAINDER OF THE WEEK.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...NONE.

$$

PUBLIC FORECAST: DYKEMA
AVIATION: CANEPA
MARINE: SIMS

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