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

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000
FXUS66 KMTR 281624
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
824 AM PST SAT FEB 28 2015

.SYNOPSIS...A STORM SYSTEM WILL BRING SHOWERS AND COOLER
TEMPERATURES TO THE AREA THROUGH TONIGHT. ANOTHER WEAK SYSTEM WILL
BRING ADDITIONAL SHOWER CHANCES TO THE AREA ON MONDAY.

&&

.DISCUSSION...AS OF 8:20 AM PST SATURDAY...AS EXPECTED SHOWERS
ACROSS OUR CWA THIS MORNING HAVE MAINLY BEEN FOCUSED ON THE
SOUTHERN THIRD OF OUR CWA. ISSUED A PNS EARLIER WITH 24 HOUR
RAINFALL TOTALS HIGHLIGHTING AMOUNTS UP TO HALF AN INCH IN
MONTEREY COUNTY. KOAK SOUNDING THIS MORNING CAME ACROSS WITH
LIFTED VALUES OF -.6 AND CAPE NEAR 400 J/KG SO THE ATMOSPHERE IS
PRIMED FOR SHOWERS AND POSSIBLE THUNDERSTORMS FOR TODAY. 15Z HRRR
IS IN GOOD AGREEMENT WITH THE FORECAST WITH KEEPING MOST OF THE
SHOWER ACTIVITY SOUTH OF THE SF BAY REGION THROUGH THE DAY AS THE
UPPER LOW PROGRESSES NORTH TO SOUTH THROUGH OUR AREA. SMALL HAIL
AND BRIEF HEAVY RAIN WILL REMAIN THE MAIN RISKS WITH MINOR
SNOW ACCUMULATIONS LIKELY FOR ELEVATIONS OVER 4000 FEET.

CURRENT FORECAST APPEARS TO BE GENERALLY ON TRACK SO MAIN FOCUS
WILL BE MONITORING RADAR PLUS SOCIAL MEDIA AND PRODUCT UPDATES.

.PREVIOUS DISCUSSION...AN UPPER TROUGH CONTINUES TO SAG SOUTH
OVER NORTHERN CALIFORNIA. TWO UPPER LEVEL LOW CENTERS ARE ROTATING
WITHIN THIS TROUGH. SHOWERS ASSOCIATED WITH THE SOUTHERN-MOST LOW
CENTER CONTINUE TO MOVE SOUTHEASTWARD OVER THE COASTAL WATERS AND
OVER SAN MATEO...SANTA CRUZ AND MONTEREY COUNTIES. MEASURABLE
RAINFALL SO FAR HAS BEEN LIMITED TO MONTEREY COUNTY...MOUNT TORO
HAS PICKED UP THE MOST THUS FAR WITH 0.35 OVER THE LAST 12 HOURS.
EXPECT SHOWER ACTIVITY TO INCREASE TODAY...BUT CONTINUE TO BE MOST
NUMEROUS ACROSS THE SOUTHERN HALF OF THE DISTRICT. THUNDERSTORMS
WILL BE POSSIBLE TODAY THROUGH THIS EVENING IN THIS UNSTABLE
AIRMASS. RAINFALL AMOUNTS ARE EXPECTED TO BE LESS THAN ONE-TENTH
OF AN INCH FOR THE SFO BAY AREA WITH ONE- QUARTER TO ONE-HALF INCH
TO THE SOUTH.

SHOWER CHANCES WILL DIMINISH OVER THE SFO BAY AREA DURING THE
NIGHT SATURDAY BUT CHANCES WILL CONTINUE SOUTH OF THE SFO BAY
AREA ALONG WITH POSSIBLE THUNDERSTORMS AND SMALL HAIL. SNOW
LEVELS WILL LOWER TO AROUND 4000 FEET SO THE HIGHER MOUNTAINS COULD
SEE A DUSTING OF SNOW. SHOWER ACTIVITY IS EXPECTED TO LARGELY END BY
SUNDAY EXCEPT FOR RESIDUAL SHOWERS POSSIBLE OVER THE SANTA LUCIA
AND SAN BENITO MOUNTAINS.

A SECOND UPPER LEVEL SYSTEM WILL MOVE INTO THE AREA MONDAY
BRINGING ADDITIONAL RAIN CHANCES TO THE AREA. LATEST COMPUTER
MODELS HAVE THIS SYSTEM TRACKING QUICKLY SOUTHWARD ALONG THE COAST
WITH PRECIP EXITING THE DISTRICT BY TUESDAY MORNING. TEMPERATURES
WILL REMAIN COOL THROUGH EARLY NEXT WEEK. HIGH PRESSURE IS
PROGGED TO REBUILD OVER THE WEST COAST FROM MIDWEEK ON. THIS WILL
USHER IN A WARMING AND DRYING TREND. WILL BUILD BACK TO OUR REGION
WEDNESDAY AS THE STORM TRACK MOVE

&&

.AVIATION...AS OF 4:05 AM PST SATURDAY...A STORM SYSTEM IS PASSING
OVER THE FORECAST AREA THIS MORNING...PROMOTING SHOWERS IN AND
AROUND THE MONTEREY BAY AREA. COOL AIR ALOFT ASSOCIATED WITH THIS
STORM SYSTEM WILL ALLOW FOR SHOWERS TO POP UP OVER THE SAN
FRANCISCO BAY AREA AND THE MONTEREY BAY AREA LATER THIS MORNING
INTO THE AFTERNOON AND EARLY EVENING HOURS. THE SHOWERS WILL BE
PERIODIC IN NATURE AND WILL RESULT IN OCCASIONAL WET RUNWAYS.

VICINITY OF KSFO...SHOWERS WILL BE IN THE VICINITY OF THE
TERMINALS THIS MORNING WITH SHOWERS IMPACTING THE TERMINALS
PERIODICALLY THROUGHOUT THE DAY TODAY. CIGS SHOULD REMAIN VFR WITH
OCCASIONAL MVFR DURING PERIODS OF HEAVIER SHOWERS. WESTERLY WINDS
ARE EXPECTED TO PREVAIL TODAY...REACHING 10 TO 15 KT.

CONFIDENCE IS MODERATE.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...SHOWERS WILL PERIODICALLY IMPACT THE
TERMINALS THROUGHOUT THE DAY TODAY. CIGS SHOULD REMAIN VFR WITH
OCCASIONAL MVFR DURING PERIODS OF HEAVIER SHOWERS. WESTERLY WINDS
ARE EXPECTED TO PREVAIL TODAY...REACHING 10 TO 15 KT.

CONFIDENCE IS MODERATE.

&&

.MARINE...AS OF 2:35 AM PST SATURDAY...A STORM SYSTEM WILL
CONTINUE TO MOVE OVER THE COASTAL WATERS TODAY PROMOTING A
POSSIBILITY OF SHOWERS AND ISOLATED THUNDERSTORMS. NORTHERLY WINDS
WILL DECREASE THROUGHOUT THE DAY AS THE CENTER OF THE STORM SYSTEM
PASSES BY. THE DECREASING WINDS WILL RESULT IN IMPROVING SEA
CONDITIONS OVERNIGHT INTO SUNDAY. NORTHERLY WINDS WILL INCREASE
ONCE AGAIN MONDAY AS THE SURFACE PRESSURE GRADIENT INCREASES.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PT REYES 10-60 NM
             SCA...PT REYES TO PIGEON PT 10-60 NM UNTIL 3 PM
             SCA...PIGEON PT TO PT PINOS 10-60 NM UNTIL 3 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM UNTIL 3 PM

&&

$$

PUBLIC FORECAST: BELL/SIMS
AVIATION/MARINE: LARRY

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