Flash Flood Warning 1, NWS San Francisco Bay Area, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
417 AM PST TUE FEB 17 2009

.DISCUSSION...AS OF 4:00 AM PST TUESDAY...VERY ACTIVE NIGHT WITH
WIDESPREAD SHOWERS THROUGHOUT THE DISTRICT. FORTUNATELY THESE
SHOWERS HAVE BEEN MOVING VERY FAST SO THERE HAS BEEN NOT BEEN ONE
PARTICULAR AREA GETTING HIT WITH A LOT OF RAIN. AN UPPER LEVEL LOW
IS CENTERED 100 MILES WNW OF SAN FRANCISCO AND MOVING EAST. BASED ON
EXTRAPOLATIONS...THE LOW WILL MOVE ACROSS THE SFO BAY AREA BETWEEN
15Z AND 18Z. BETWEEN NOW AND THEN EXPECT ABUNDANT SHOWER ACTIVITY
WITH ISOLATED THUNDERSTORMS AND SMALL HAIL. THERE COULD BE SOME
STRONG THUNDERSTORMS DUE TO A VERY UNSTABLE AIRMASS WITH THE
500MB TEMPERATURE AT AROUND -26C. SNOW LEVELS WILL BE AROUND 3500
FEET BUT SNOW COULD FALL TO LOWER LEVELS IN AREAS OF STRONG
CELLS. WATERSPOUTS ARE POSSIBLE OVER THE COASTAL WATERS AS WELL.

IN THE BURN AREAS...RADAR SHOWS LOTS OF SHOWERS HAVE MOVED OVER THAT
AREA BUT THE SHOWERS ARE MOVING SO FAST THAT RAIN GAGES HAVE SHOWN
LITTLE RAINFALL ACCUMULATION. PERSONS IN THE BURN AREA SHOULD
STILL KEEP A CLOSE EYE ON THE LATEST FORECAST THIS MORNING AS SOME
STRONG CELLS COULD FORM OVER THE AREA PRODUCING LOCALLY HEAVY RAIN.

SHOWERS ACTIVITY WILL DECREASE THIS AFTERNOON AND EVENING AS
THE LOW MOVES INLAND. THE NEXT UPPER LOW IS FORECAST TO DEEPEN ALONG
140W AND BECOME NEARLY STATIONARY. THE POSITION OF THIS UPPER LOW
WILL ALLOW A RIDGE TO BUILD OVER THE STATE LATE TONIGHT THROUGH
THURSDAY. THEREFORE DRIER AND WARMER WEATHER IS EXPECTED WEDNESDAY
AND THURSDAY. THE UPPER LOW OVER THE CENTRAL PACIFIC WILL START TO
MOVE EAST FRIDAY BRINGING A CHANCE OF RAIN TO THE AREA THIS WEEKEND.
WILL HAVE TO WATCH THIS SYSTEM OVER THE NEXT COUPLE OF DAYS FOR
POSSIBLY SOME SUBTROPICAL MOISTURE GETTING ENTRAINED INTO THE
SYSTEM BRINGING HEAVY RAIN TO THE AREA ALONG WITH THE ASSOCIATED
HYDRO PROBLEMS...PARTICULARLY FOR THE BURN AREAS.

&&

.AVIATION......AS OF 3:35 AM PST TUESDAY...FAST MOVING STORMS (APPROX
25 KT) WILL CONTINUE TO MOVE FROM SW TO NE ACROSS THE FORECAST AREA.
AS A RESULT...BRIEF HEAVY RAIN...GUSTY WINDS AND POSS SMALL HAIL
MAY ACCOMPANY THESE STORMS. DESPITE HEAVY DOWNPOURS...RECENT OBS DO
NOT INDICATE REALLY LOW CIGS SO MVFR CONDITIONS SHOULD REMAIN EVEN
WITH A QUICK MOVING SHOWER. THE THREAT FOR THESE STORMS WILL
CONTINUE THROUGH ABOUT 18-20Z THIS AFTERNOON UNTIL THE COLD UPPER
LOW MOVES INLAND.  DURING THIS TIME PERIOD...CIGS SHOULD SCT OUT
AND WOULD NOT BE SURPRISED OF SOME TERMINALS GO SKC.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
      .TDY...SCA...PT ARENA TO PT PIEDRAS BLANCAS 20 TO 60 NM 10 AM.
            .SCA...SF BAY 10 AM.
            .SCA...POINT REYES TO PT PIEDRAS BLANCAS 0 TO 20 NM 10
                   AM.
            .SCA...FOR ROUGH BAR CONDITIONS 10 AM.

&&

PUBLIC FORECAST: STROBIN/W PI
AVIATION/MARINE: MEHLE

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1055 AM PST MON FEB 16 2009

CAZ006-505>513-516>518-528>530-171900-
SAN FRANCISCO-
COASTAL NORTH BAY...INCLUDING POINT REYES NATIONAL SEASHORE-
NORTH BAY INTERIOR VALLEYS-NORTH BAY MOUNTAINS-
SAN FRANCISCO BAY SHORELINE-SAN FRANCISCO PENINSULA COAST-
EAST BAY INTERIOR VALLEYS-EAST BAY HILLS AND DIABLO RANGE-
SANTA CRUZ MOUNTAINS-SANTA CLARA VALLEY...INCLUDING SAN JOSE-
SOUTHERN SALINAS VALLEY...ARROYO SECO...AND LAKE SAN ANTONIO-
SANTA LUCIA MOUNTAINS AND LOS PADRES NATIONAL FOREST-
MOUNTAINS OF SAN BENITO AND INTERIOR MONTEREY COUNTY INCLUDING
PINNACLES NATIONAL MONUMENT-
NORTHERN SALINAS VALLEY...HOLLISTER VALLEY...AND CARMEL VALLEY-
NORTHERN MONTEREY BAY-SOUTHERN MONTEREY BAY AND BIG SUR COAST-
1055 AM PST MON FEB 16 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SAN FRANCISCO BAY AREA AND
MONTEREY BAY AREA.

.DAY ONE...MONDAY AND MONDAY NIGHT

DUE TO RECENT RAINFALL...SMALL ROCK SLIDES AND MINOR DEBRIS FLOWS
CAN BE EXPECTED THROUGH THE MORNING. AFTER A BREAK IN THE
SHOWERS...ANOTHER ROUND OF RAIN WILL RETURN TO THE DISTRICT
TONIGHT. HEAVY RAIN... SMALL HAIL... AND GUSTY WINDS ARE POSSIBLE
WITH THESE STORMS. LOCALIZED FLOODING WILL BE POSSIBLE AGAIN. IF
THE MAIN BAND OF SHOWERS SETS UP OVER THE BURN AREAS THERE WILL BE
THE POTENTIAL FOR DEBRIS FLOWS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SHOWERS WILL END LATE TUESDAY AFTERNOON. THERE IS A POTENTIAL FOR
LOCALIZED FLOODING THROUGH EARLY TUESDAY AFTERNOON. RAINFALL
TOTALS THROUGH TUESDAY ARE EXPECTED TO BE UP TO AN INCH OVER URBAN
AREAS WITH UP TO THREE INCHES POSSIBLE OVER HIGHER ELEVATION LOCATIONS.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS PER STANDARD OPERATING PROCEDURES.

BELL