Severe Thunderstorm Warning 7, NWS San Francisco Bay Area, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
400 AM PST THU DEC 30 2004

.DISCUSSION...THREE IMPULSES ROTATING AROUND THE UPPER LOW ANCHORED
OVER THE PACIFIC NORTHWEST HAVE AFFECTED OR ARE GOING TO AFFECT OUR
DISTRICT OVER THE NEXT SEVERAL DAYS. THE FRONTAL BAND ASSOCIATED
WITH THE FIRST IMPULSE HAS PRETTY MUCH MOVED THROUGH THE DISTRICT...
HOWEVER NOW WE ARE UNDER THE UNSTABLE REGION BEHIND THIS FRONT WITH
NUMEROUS SHOWERS AND EVEN A FEW THUNDERSTORMS OCCURRING. THERE HAVE
ALSO BEEN SOME REPORTS OF LIGHTNING AND SMALL HAIL IN SONOMA COUNTY
EARLIER THIS MORNING. LATEST RADAR IMAGERY SHOWS A 50+ dBZ CELL
MOVING OVER THE NORTHERN PORTION OF SAN FRANCISCO. THESE CONVECTIVE
CELLS ARE MOVING AT ABOUT 32 KNOTS TO THE NORTHEAST...SO THE
DOWNPOURS AND POSSIBLE SMALL HAIL SHOULD BE BRIEF IN DURATION. THE
SHOWER ACTIVITY IS EXPECTED TO CONTINUE THROUGHOUT THE DAY WITH THE
SECOND IMPULSE ROTATING AROUND THE LOW BRINGING AN ORGANIZED FRONT
THROUGH THE DISTRICT LATER TONIGHT. THE 00Z AND 06Z ETA AND GFS
INDICATE RAIN WILL INCREASE IN THE NORTH BAY AGAIN THIS EVENING...AND
SPREAD SOUTHWARD THROUGH THE REST OF THE DISTRICT OVERNIGHT. THE
THIRD DISTURBANCE WILL THEN SWING THROUGH THE ON FRIDAY FOLLOWED BY A
BRIEF BREAK IN THE ACTION FRIDAY NIGHT INTO SATURDAY. ON SATURDAY...
ANOTHER UPPER LOW IS FORECAST TO DROP DOWN FROM THE PACIFIC NORTHWEST
BRINGING ANOTHER ROUND OF RAINFALL TO THE AREA LATE IN THE DAY
TAPERING OFF TO SHOWERS BY SUNDAY. THE MEAN TROUGH POSITION OVER THE
WEST COAST WILL KEEP RAIN CHANCES CONTINUING THROUGH MIDWEEK.

MEDIUM RANGE MODELS INDICATE THE TROUGH WILL FINALLY MOVE EAST INTO
THE GREAT BASIN BY MIDWEEK WITH AN OMEGA BLOCKING RIDGE SETTING UP
OFF THE COAST. HOWEVER...LATEST GFS ENSEMBLE MEANS INDICATE AN
UNDERCUTTING WESTERLY FLOW LATER IN THE WEEK AND INTO THE FOLLOWING
WEEKEND FOR CONTINUED WET WEATHER POTENTIAL.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
    .TDA...GALE WARNING FOR SAN FRANCISCO BAY
        ...SCA...PT ARENA TO PT PIEDRAS BLANCAS AND MONTEREY BAY.

PUBLIC FORECAST: ANDERSON
MARINE/AVIATION: PI

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO (ALL LOWER CASE)

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
545 AM PST THU DEC 30 2004

CAZ005>010-065-074-075-311400-
SONOMA AND MARIN COUNTIES-SAN FRANCISCO-
ALAMEDA AND CONTRA COSTA COUNTIES-SANTA CLARA COUNTY-
COASTAL MONTEREY COUNTY-
SALINAS VALLEY/INTERIOR MONTEREY COUNTY/SAN BENITO COUNTY-
NAPA COUNTY-SANTA CRUZ COUNTY-SAN MATEO COUNTY-
545 AM PST THU DEC 30 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE SAN FRANCISCO AND MONTEREY
BAY AREAS

.DAY 1...TODAY

A MOIST AND UNSTABLE AIRMASS WILL KEEP SHOWERS AND THUNDERSTORM
CHANCES ACROSS THE AREA TODAY. SMALL HAIL IS POSSIBLE IN THE
THUNDERSTORMS...AND URBAN OR SMALL STREAM FLOODING IS POSSIBLE THIS
MORNING IN PORTIONS OF THE SAN FRANCISCO PENINSULA...THE SANTA CRUZ
MOUNTAINS...AND THE EAST AND SOUTH BAY AREAS. RAIN WILL INCREASE
ACROSS THE AREA TONIGHT AS ANOTHER COLD FRONT MOVES ACROSS THE
DISTRICT.

ALSO...BY LATE TONIGHT A LARGE SWELL TRAIN IS FORECAST TO REACH THE
COAST AND HIGH SURF ADVISORIES MAY BE ISSUED.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A LARGE SWELL TRAIN IS FORECAST TO AFFECT THE COAST FRIDAY AND
FRIDAY NIGHT AND HIGH SURF ADVISORIES MAY BE ISSUED.

A BRIEF BREAK IN THE WET WEATHER IS FORECAST LATER FRIDAY INTO NEW
YEARS DAY. HOWEVER WET AND UNSETTLED WEATHER IS FORECAST TO RETURN
SUNDAY THROUGH TUESDAY. GIVEN ALL OF THE RECENT RAIN...FLOODING
CONCERNS WILL HAVE TO BE MONITORED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

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