915 WWUS86 KMTR 250501 SPSMTR SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1001 PM PDT THU MAY 24 2012 CAZ006-505>513-516>518-528>530-251500- 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- 1001 PM PDT THU MAY 24 2012 ...MUCH COOLER WITH A CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS FRIDAY... AN UNSEASONABLY COLD WEATHER SYSTEM WILL RAPIDLY APPROACH THE BAY AREA OVERNIGHT...ARRIVING BY FRIDAY MORNING. RAIN SHOWERS CURRENTLY ASSOCIATED WITH THIS SYSTEM ARE BEING REPORTED IN SOUTHERN OREGON WITH RADARS WEST OF CAPE MENDOCINO STARTING TO PICK UP RETURNS. THE MAIN IMPACT OF THE SYSTEM WILL BE COOL TEMPERATURES AND A CONTINUATION OF THE BREEZY TO LOCALLY WINDY WEATHER WE'VE BEEN HAVING THE LAST FEW DAYS. SKIES WILL START OUT SUNNY BUT WITH COLD MORNING TEMPERATURES IN THE UPPER 30S AND 40S FOR MANY PORTIONS OF THE BAY AREA. BY MID-MORNING THE CORE OF THE SYSTEM WILL PASS OVERHEAD WITH VERY UNSTABLE AIR ALOFT. THIS WILL ALLOW FOR CUMULUS CLOUD DEVELOPMENT OVER THE HILLS OF THE BAY AREA. RAIN SHOWERS WILL BE POSSIBLE THROUGH THE AFTERNOON HOURS...ESPECIALLY OVER THE HILLS BUT ITS POSSIBLE THAT ANY SHOWERS COULD DRIFT OVER THE VALLEYS. ANYBODY WITH OUTDOOR INTERESTS SUCH AS CAMPING OUR HIKING ON FRIDAY SHOULD BE PREPARED FOR UNSEASONABLY COOL...POSSIBLY WET AND WINDY WEATHER. FINALLY...THE LATEST COMPUTER MODEL PROJECTIONS HAVE BEEN CONSISTENT IN SHOWING AN ABOVE AVERAGE CHANCE OF THUNDERSTORMS OVER THE FAR EASTERN PORTIONS OF OUR DISTRICT...ROUGHLY RUNNING SOUTHWARD FORM THE HILLS OF NAPA COUNTY THROUGH THE FAR EAST BAY VALLEYS AND CONTINUING SOUTHWARD OVER THE HIGHER AND MOSTLY UNPOPULATED AREAS OF SANTA CLARA AND SAN BENITO COUNTIES. THESE FAR EASTERN COUNTIES OF THE BAY AREA WILL HAVE THE BEST CHANCE FOR SEEING THUNDERSTORMS ROUGHLY FROM 2 PM TO 7 PM FRIDAY AFTERNOON AND EVENING. FREEZING LEVELS WILL DROP TO AROUND 6000 FEET SO ICE PELLETS AND SMALL HAIL WILL BE POSSIBLE IN SOME OF THE HEAVIER CELLS ALONG WITH DANGEROUS CLOUD TO GROUND LIGHTNING. ANY HAIL THAT FALLS ON ROADS CAN QUICKLY LEAD TO TRAFFIC ACCIDENTS...ESPECIALLY ON THE GET AWAY FRIDAY OF A THREE DAY HOLIDAY WEEKEND. THE NATIONAL WEATHER SERVICE AND CALIFORNIA HIGHWAY PATROL URGE MOTORISTS TO SLOW DOWN AND STAY ABREAST OF THE LATEST FORECAST INFORMATION BEFORE HEADING OUT THIS HOLIDAY WEEKEND. AS A REMINDER...FOLKS HEADING TO THE SIERRA SHOULD EXPECT WINTER WEATHER CONDITIONS FRIDAY NIGHT INTO SATURDAY WITH SNOW OVER THE TRANS-SIERRA PASSES. THERE ARE CURRENTLY SNOW ADVISORIES IN EFFECT FOR THAT WEST SLOPE OF THE SIERRA UNTIL 6 PM FRIDAY. HTTP://WEATHER.GOV/SANFRANCISCO $$ R WALBRUN