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

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FXUS66 KMTR 271633
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
833 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 4:02 AM PST FRIDAY...CURRENTLY THE IR SATELLITE
IMAGE IS SHOWING SOME HIGH CLOUDS PASSING OVER THE WEST COAST. THE
GOES MVFR PROBABILITY PRODUCT IS INDICATING CIGS ALONG THE COAST
AND IN THE SANTA CLARA VALLEY. THE SURFACE PRESSURE GRADIENT IS
WEAKER THAN IT WAS AT THIS HOUR YESTERDAY BUT AN APPROACHING STORM
SYSTEM SHOULD PROVIDE ENOUGH MIXING TO PREVENT WIDESPREAD STRATUS
FROM FORMING IN THE SAN FRANCISCO BAY AREA. STRATUS IS APPARENT
IN THE MONTEREY BAY AREA BUT SHOULD LIFT AS THE STORM SYSTEM MOVES
CLOSER TO THE AREA.

VICINITY OF KSFO...VFR IS ANTICIPATED TO PREVAIL TODAY WITH
SCT025 PASSING OVER THE TERMINALS AND APPROACH THROUGHOUT THE DAY
TODAY. STRONG WEST WINDS ARE EXPECTED TO REACH 25 TO 30 KT THIS
AFTERNOON WITH GUSTS TO 38 KT.

CONFIDENCE IS MODERATE.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...MVFR CIGS BKN-OVC015 ARE ANTICIPATED
TO LIFT TO BKN035 LATER THIS MORNING AS A STORM SYSTEM APPROACHES
THE FORECAST AREA. WEST WINDS WILL INCREASE TO 15 KT THIS
AFTERNOON WITH GUSTS TO 25 KT.

CONFIDENCE IS MODERATE.

&&

.MARINE...AS OF 8:30 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: LARRY
MARINE: MM

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