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

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000
FXUS66 KMTR 041547
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
847 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 4:18 AM PDT MONDAY...DEEP MARINE LAYER IN PLACE
WITH MOST TERMINALS REPORTING MVFR CONDITIONS...KSTS HAS SOME
PATCHY FOG DROPPING THEM INTO IFR. EXPECT CIGS TO LAST THROUGH
MUCH OF THE MORNING RUSH GIVEN THE DEEP NATURE OF THE STRATUS AND
CONTINUED ONSHORE FLOW. VFR FOR A BRIEF PERIOD THIS AFTERNOON WITH
CIGS RETURNING TONIGHT.

VICINITY OF KSFO...CIGS AROUND 1500 FEET WILL LAST THROUGH AT
LEAST 18Z...BUT MORE LIKELY THROUGH 19-20Z. VFR THIS AFTERNOON
WITH GUSTY ONSHORE FLOW. EXPECT A RETURN OF CIGS TONIGHT BEFORE
06Z.

SFO BRIDGE APPROACH...CIGS MAY BE A TOUCH HIGH OVER THE APPROACH
THIS MORNING...NEAR 2K FT. POSSIBLE THAT CIGS MAY LINGER SLIGHTLY
LONGER OVER THE APPROACH. AS WELL. POSS AN HOUR AFTER KSFO
CLEARS. SIMILAR TO SFO.

MONTEREY BAY AREA TERMINALS...MVFR CIGS THROUGH AT LEAST 18Z.
STILL SOME UNCERTAINTY...BUT IT IS POSSIBLE THAT KMRY MAY NOT
CLEAR AT ALL TODAY.  EARLY RETURN OF CIGS TONIGHT.

&&

.MARINE...AS OF 04:12 AM PDT MONDAY...NORTHERLY WINDS WILL
INCREASE OVER THE COASTAL WATERS TODAY AS HIGH PRESSURE BUILDS OFF
THE WEST COAST. THE INCREASING WINDS WILL PRODUCE STEEP WIND WAVES
AND FRESH SWELL. WINDS WILL GRADUALLY WEAKEN LATER THIS WEEK AS
HIGH PRESSURE WEAKENS. A LONG PERIOD SOUTHERLY SWELL WILL CONTINUE
TO IMPACT THE COASTAL WATERS TODAY.

&&

.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/BELL
AVIATION/MARINE: MM

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