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

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000
FXUS66 KMTR 041839
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1139 AM PDT MON MAY 4 2015

.SYNOPSIS...A DEEP MARINE LAYER WILL MAINTAIN LOW CLOUDS AND FOG
ALONG THE COAST AND INLAND VALLEYS THROUGH AT LEAST WEDNESDAY. A
TROUGH OF LOW PRESSURE WILL PASS OVER THE AREA MIDWEEK MIXING OUT
THE MARINE LAYER AND PROMOTING A SLIGHT CHANCE OF SHOWERS AROUND
THE AREA...ESPECIALLY OVER THE MOUNTAINS. OTHERWISE EXPECT
SLIGHTLY BELOW NORMAL TEMPERATURES CONTINUING THROUGH THE WEEK.

&&

.DISCUSSION...AS OF 08:41 AM PDT MONDAY...VISIBLE SATELLITE
IMAGERY SHOWS WIDESPREAD LOW CLOUD COVER ACROSS MUCH OF THE REGION
THIS MORNING AS A RESULT OF THE DEEP MARINE LAYER. EXPECTING BURN-
OFF TO BE SLOW THROUGH THE MORNING WITH MANY COASTAL LOCATIONS
REMAINING UNDER CLOUD COVER FOR MUCH OF THE DAY. THIS WILL KEEP
TEMPERATURES COOL BENEATH THE CLOUD COVER...WHILE INLAND AREAS
THAT BREAK OUT FROM THE CLOUDS WARM INTO THE UPPER 60S TO LOWER
70S. THE ONGOING FORECAST THIS MORNING APPEARS TO BE ON TRACK AND
NO CHANGES ARE NEEDED AT THIS TIME.

&&

.PREV DISCUSSION...AS OF 3:00 AM PDT MONDAY...FORT ORD PROFILER
SHOWS THAT THE MARINE LAYER HAS REMAINED FAIRLY STEADY OVER THE
PAST 12 HOUR AROUND 3000 FEET. THAT COMBINED WITH A GENERAL NW
SURFACE FLOW HAS ALLOWED WIDESPREAD CLOUDS ACROSS OUR CWA
OVERNIGHT BOTH ALONG THE COAST AND ADJACENT VALLEYS. SATELLITE
IMAGES HAVE IT EXTENDING THROUGH MOST OF THE EAST BAY AND TO MOST
OF THE SALINAS VALLEY. SO FAR HAVE NOT RECEIVED ANY REPORTS OF
REDUCED VIS DUE TO FOG ALTHOUGH WOULD EXPECT AT LEAST A FEW SPOTS
BY MORNING. CLOUDS WILL BE SLOW TO BURN OFF AND WILL LIKELY BE
NEAR THE COAST THROUGH THE ENTIRE DAY. THIS WILL LEAD TO COOL
TEMPS WITH 50S TO MID 60S AT THE COAST WHILE INLAND MID 60S TO MID
70S WILL BE COMMON.

SYNOPTICALLY LITTLE WILL CHANGE OVER THE NEXT FEW DAYS AS THE
MARINE LAYER REMAINS WELL OVER 2000 FEET WHILE THE SURFACE FLOW
FAVORS AN ONSHORE FLOW. GUIDANCE ALSO SUGGESTS SOME PATCHY DRIZZLE
FOR TONIGHT INTO EARLY TUESDAY FOR SPOTS SOUTH OF SF BAY. HIGHS
SHOULD STAY WITHIN A FEW DEGREES OF WHAT WE WILL SEE TODAY.

AN UPPER LEVEL LOW WILL DIVE DOWN FROM THE NORTH ON THURSDAY WHICH
SHOULD HELP TO MIX OUT OR AT LEAST GREATLY DECREASE THE INFLUENCE
OF THE MARINE LAYER. MOST OF THE MOISTURE AND FAVORED INSTABILITY
WILL REMAIN TO OUR EAST HOWEVER MODELS DO BRING THE WESTERN EXTENT
NEAR OUR AREA. THERE REMAIN MODEL DISCREPANCY ON THE TRACK OF THE
LOW WHICH WILL BE THE KEY FACTOR IN HOW MUCH...IF ANY...OF THE
MOISTURE MAKES IT HERE. ONLY DID A FEW MINOR ADJUSTMENTS TO THE
POPS AT THIS TIME. EVEN THE MOST BULLISH PROJECTIONS BRING A TENTH
OF AN INCH AT BEST OVER THE MOUNTAINS. THE LOW IS FORECAST TO
HEAD TO NEVADA BY FRIDAY.

FOR THE UPCOMING WEEKEND INTO NEXT WEEK...FAIRLY QUIET WEATHER
APPEARS TO BE ON TAP. TEMPS WILL AVERAGE NEAR OR JUST A BIT BELOW
NORMAL.

&&

.AVIATION...AS OF 11:39 AM PDT MONDAY...FOR 18Z TAFS. DEEP MARINE
LAYER IS LEADING TO SLOW BURN OFF TODAY. HAVE GONE WITH 21Z FOR
KSFO WITH LITTLE OR NO HOPE FOR CLEARING AROUND MONTEREY BAY.
GRADIENTS ARE LIGHT AT THE MOMENT BUT MODELS SHOW STRONG SEABREEZE
THIS AFTERNOON SO ONCE CLEARING OCCURS CONCERNED THAT CIGS WILL
RETURN EARLY AGAIN TONIGHT EVEN THOUGH CEILINGS SHOULD REMAIN
ABOVE IFR THRESHOLDS.

VICINITY OF KSFO...TAF WILL SHOWS 21Z FOR SCT OCCURRING. CONF IS
MODERATE. SOME CONCERN THAT CIGS COULD EVEN LINGER LONGER. WILL
CONTINUE TO MONITOR. SET UP LOOKS RIPE FOR LOW CIGS RETURNING FOR
THE EVENING RUSH. CURRENT TAF SHOWS 04Z.

SFO BRIDGE APPROACH...NOT TOO DIFFERENT THAN THE TERMINAL. SLOW
CLEARING STRATUS THROUGH AT LEAST 2030Z.

MONTEREY BAY AREA TERMINALS...LATEST TAFS HAVE KEPT CIGS IN ALL
DAY AT KMRY AND KSNS BUT WILL SHOW A TEMPO SCT GROUP. LOW
CONFIDENCE ON THAT. ANY CLEARING WOULD BE SHORT LIVED WITH STRATUS
FILLING BACK IN QUICKLY LATE THIS AFTERNOON/EVENING.

&&

.MARINE...AS OF 10:42 AM PDT MONDAY...A LONG PERIOD SOUTHERLY
SWELL CURRENTLY MOVING THROUGH THE WATERS WILL BEGIN TO DISSIPATE
BY THIS AFTERNOON. NORTHERLY WINDS WILL  INCREASE OVER THE COASTAL
WATERS LATER THIS AFTERNOON AND EVENING AS HIGH PRESSURE BUILDS
OFF THE WEST COAST. THE INCREASING WINDS WILL PRODUCE STEEP WIND
WAVES AND FRESH SWELL THROUGH MIDWEEK. WINDS WILL GRADUALLY EASE
LATER THIS WEEK AS HIGH PRESSURE WEAKENS.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PT REYES 10-60 NM
             SCA...PT ARENA TO PT REYES 0-10 NM FROM 3 PM
             SCA...PT REYES TO PIGEON PT 0-10 NM FROM 3 PM
             SCA...PT REYES TO PIGEON PT 10-60 NM FROM 3 PM
             SCA...SF BAY NORTH OF THE BAY BRIDGE FROM 1 PM

&&

$$

PUBLIC FORECAST: RGASS
AVIATION/MARINE: RWW

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