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

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000
FXUS66 KMTR 271751
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
951 AM PST FRI FEB 27 2015

.SYNOPSIS...A STORM SYSTEM WILL BRING SHOWERS AND COOLER
TEMPERATURES TO THE AREA STARTING LATER TODAY AND CONTINUE THROUGH
THE WEEKEND. ANOTHER WEAK SYSTEM WILL BRING ADDITIONAL SHOWER
CHANCES TO THE AREA ON MONDAY.

&&

.DISCUSSION...AS OF 8:30 AM PST FRIDAY...TRANQUIL WEATHER
CONDITIONS ACROSS OUR AREA TODAY AS THE STORM SYSTEM THAT WILL
BRING SHOWERS TO OUR AREA REMAINS WELL TO OUR NORTH. DID AN UPDATE
TO THE FORECAST TO REMOVE SHOWERS FOR THIS MORNING AND HAD THEM
DELAYED BY SEVERAL HOURS FOR THE AFTERNOON.

MAIN CONCERN REMAINS FOR LATE TONIGHT THROUGH SATURDAY NIGHT AS
THE LOW WILL PROGRESS SOUTHWARD OVER OUR AREA HELPING TO
DESTABILIZE THE ATMOSPHERE. WITH MUCAPE VALUES FORECAST TO LOCALLY
EXCEED 300 J/KG AND LIFTED VALUES DOWN TO LESS THAN MINUS
2...SMALL HAIL CAN BE EXPECTED WITH SOME OF THE CELLS. SPC HAS
HIGHLIGHTED OUR ENTIRE AREA LATE TONIGHT THROUGH SAT NIGHT FOR THE
POTENTIAL OF CONVECTION. STILL FEEL THE BEST SHOT WILL BE OVER THE
SOUTHERN THIRD OF THE CWA ESPECIALLY MONTEREY COUNTY AND ADJACENT
WATERS SATURDAY. DO AGREE WITH SPC THAT THUNDER WILL ALSO BE
POSSIBLE ON SUNDAY FOR INTERIOR MONTEREY COUNTY.

GFS/ECMWF CURRENTLY DISAGREE WITH THE STORM ON MONDAY AS A
SHORTWAVE TROF DIVES DOWN FROM THE NORTH. GFS REMAINS MUCH DRIER
WHILE THE ECMWF SHOWS ANOTHER ROUND OF SHOWERS FOR MOST OF OUR
AREA. HOPEFULLY 12Z RUNS WILL BE IN BETTER AGREEMENT.

.PREVIOUS DISCUSSION...SURFACE PRESSURE GRADIENTS HAVE SWITCHED
MORE TO ONSHORE OVER THE PAST 24 HOURS...AND DEW POINT AND AMBIENT
TEMPERATURES HAVE INCREASED BY AS MANY AS 10 DEGREES FROM
YESTERDAY AT THIS TIME. SATELLITE IMAGERY SHOWS PARTLY CLOUDY
SKIES OVER THE DISTRICT. EXPECT CLOUDS TO INCREASE AS AN UPPER
LEVEL LOW APPROACHES THE STATE FROM THE NORTH. THIS LOW WILL BRING
IN COLDER AIR ALOFT AND A SLIGHT CHANCE OF SHOWERS TO THE AREA
LATER TODAY. SHOWER CHANCES WILL INCREASE FRIDAY NIGHT AND
SATURDAY WHEN THE UPPER LOW MOVES OVER THE CENTRAL COAST. THIS
WILL ALSO DESTABILIZE THE ATMOSPHERE FURTHER FOR A SLIGHT CHANCE
OF THUNDERSTORMS SATURDAY AFTERNOON AND EVENING.

SHOWER CHANCES DECREASE SATURDAY NIGHT AS THE LOW MOVES INTO
SOUTHERN CALIFORNIA. BY THIS TIME SNOW LEVELS WILL LOWER TO 4000
FEET SO IF THERE ARE ANY SHOWERS LEFT BY THEN THERE COULD BE A
DUSTING OF SNOW ON THE HIGHEST MOUNTAINS. TOTAL RAINFALL AMOUNTS
WILL BE MEAGER...GENERALLY A QUARTER OF AN INCH OR LESS...ALTHOUGH
AMOUNTS COULD BE HIGHER ALONG THE SANTA CRUZ AND MONTEREY COUNTY
COAST AND MOUNTAINS WHERE OVER A HALF INCH IS POSSIBLE IN LOCALLY
HEAVIER SHOWERS.

PARTLY CLOUDY SKIES WITH COOL CONDITIONS ARE EXPECTED ON SUNDAY
BEFORE A SECOND SYSTEM APPROACHES FROM THE NORTH. THIS WILL BRING
ANOTHER CHANCE OF SHOWERS TO THE AREA MONDAY AND MONDAY NIGHT WITH
CONTINUED COOL TEMPERATURES. THIS SYSTEM IS EXPECTED TO MOVE
THROUGH QUICKLY WITH SHOWERS ENDING ON TUESDAY. HIGH PRESSURE
WILL THEN BUILD BACK IN OVER THE WEST BY MIDWEEK FOR A WARMING AND
DRYING TREND THROUGH THE REST OF THE WEEK.

&&

.AVIATION...AS OF 09:50 AM PST FRIDAY...COMPLEX WEATHER SET UP OVER
THE BAY AREA AS A STORM SYSTEM SLOWLY APPROACHES THE BAY AREA.
AHEAD OF THE MAIN SYSTEM...A MIX OF SCT-BKN CIGS WILL IMPACT MOST
TERMINALS THROUGH EARLY THIS AFTERNOON. ENOUGH HEATING MAY BE
PRESENT THIS AFTERNOON FOR MORE ELEVATED CIGS WITH VFR CONDITIONS.
ADDITIONALLY WINDS WILL SLOWLY RAMP UP WITH STRONG WINDS POSSIBLE
AROUND SF BAY. TONIGHT IS TRICKY...NOT SURE HOW MANY CIGS WILL BE
PRESENT GIVEN THE LACK OF DAYTIME HEATING...BUT THE APPROACHING
STORM MAY COUNTER ACT IT. NEEDLESS TO SAY LOW CONF ON CIGS TONIGHT
AND EARLY TOMORROW. MODEL GUIDANCE ALSO INDICATES SCT SHOWERS
TOMORROW AS WELL. GIVEN THE SPOTTY NATURE DECIDED TO DO VCSH FOR
TAFS.

OVERALL CONF IS MEDIUM.

VICINITY OF KSFO...OCCASIONAL CIGS IN THE 1500-2000 FT RANGE POSS
THIS MORNING AND THIS AFTERNOON. IF CIGS IMPACT SFO THEY SHOULD
MAINLY BE TEMPORARY AND MOVING FROM NW TO SE.
ADDITIONALLY...STRONG WEST WINDS ARE EXPECTED TO REACH 15 TO 30 KT
THIS AFTERNOON WITH GUSTS TO 35 KT. AWW HAS BEEN ISSUED FROM
21-04Z. CIGS WILL LIKELY BE ELEVATED TONIGHT AND TOMORROW IN THE
VFR CAT. VCSH POSS ON SATURDAY.


KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR CIGS GENERALLY...BUT OCCASIONAL
BKN MVFR CIGS POSSIBLE THIS MORNING AND THIS AFTERNOON. MVFR TO
VFR CIGS TONIGHT AND TOMORROW WITH VCSH.

&&

.MARINE...AS OF 09:39 AM PST FRIDAY...A STORM SYSTEM WILL APPROACH
THE REGION TODAY RESULTING IN VERY GUSTY NORTHERLY WINDS OVER
COASTAL WATERS...INCLUDING BAYS. THE GUSTY WINDS WILL PRODUCE
HAZARDOUS CONDITIONS WITH STEEP WIND WAVES AND FRESH SWELL. THE
STORM SYSTEM WILL BRING A POSSIBILITY OF SHOWERS AND THUNDERSTORMS
TO THE COASTAL WATERS BEGINNING THIS AFTERNOON LASTING INTO
SATURDAY EVENING. WINDS WILL DECREASE AND SEA CONDITIONS WILL
IMPROVE FOR A MAJORITY OF THE WATERS BY SATURDAY AFTERNOON AS THE
CENTER OF THE STORM SYSTEM PASSES ALONG THE CALIFORNIA COAST.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PT REYES 0-10 NM
             SCA...PT REYES TO PIGEON PT 0-10 NM
             SCA...PIGEON PT TO PT PINOS 0-10 NM
             SCA...PT ARENA TO PT REYES 10-60 NM
             SCA...PT REYES TO PIGEON PT 10-60 NM
             SCA...PIGEON PT TO PT PINOS 10-60 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...MONTEREY BAY FROM 1 PM
             SCA...SF BAY NORTH OF THE BAY BRIDGE FROM 10 AM
             SCA...SF BAY SOUTH OF THE BAY BRIDGE FROM 10 AM

&&

$$

PUBLIC FORECAST: BELL
AVIATION/MARINE: MM

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