Small Craft Advisory 193, NWS San Francisco Bay Area, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
857 AM PDT WED APR 1 2009

.DISCUSSION...AS OF 8:57 AM PDT WEDNESDAY...SKIES ARE MOSTLY CLEAR
OVER THE DISTRICT EXCEPT FOR HIGH CLOUDS FILTERING IN FROM THE
NORTHWEST AHEAD OF AN UPPER TROUGH APPROACHING THE PACIFIC
NORTHWEST. SURFACE PRESSURE GRADIENTS REMAIN STRONG FROM THE NORTH
THE 6.5 MB BETWEEN ARCATA AND SAN FRANCISCO...12.4 MB FROM SFO TO
LAS...WITH AN ONSHORE GRADIENT OF 1.9 MB FROM SFO TO SAC. AS A
RESULT OF THESE TIGHT GRADIENTS...WINDS ARE STRONG OVER THE COASTAL
WATERS WHERE NEAR-GALE CONDITIONS ARE OCCURRING. EXPECT THE
GRADIENTS TO TIGHTEN OVERNIGHT...ESPECIALLY IN THE ONSHORE
DIRECTION...AS A WEAK TROUGH BRUSHES ACROSS NORTHERN CALIFORNIA.
THIS IS EXPECTED TO DEEPEN THE MARINE LAYER OVERNIGHT FOR COASTAL LOW
CLOUDS FORMING AND SPREADING INLAND MOST AREAS.

HIGH PRESSURE ALOFT WILL REBUILD OVER THE EASTERN PACIFIC LATE
FRIDAY FOR A SLIGHT WARMING TREND INTO SATURDAY. A STRONGER UPPER
LEVEL TROUGH IS PROGGED TO APPROACH THE COAST ON SUNDAY FOR SHOWER
CHANCES RETURNING TO THE AREA AS EARLY AS SUNDAY NIGHT AND MONDAY.
THE GFS FEATURES A SOLUTION WITH THE UPPER TROUGH FARTHER NORTH BY
MONDAY WITH THE UPPER LOW CENTER MOVING ACROSS NORTHERN CALIFORNIA.
THE 00Z RUN OF THE ECMWF...HOWEVER...DROPS THE UPPER LOW CENTER
SOUTH OVER THE EASTERN PACIFIC...SKIRTING THE WEST COAST BEFORE
FINALLY BRINGING IT INLAND ACROSS SOUTHERN CALIFORNIA ON TUESDAY.
EITHER WAY SHOWER CHANCES LOOK OK FOR OUR ZONES LATE IN THE PERIOD.
THESE MODEL DIFFERENCES WILL NEED TO BE RESOLVED IN ORDER TO
DETERMINE TIMING AS WELL AS AMOUNTS.

&&

.AVIATION...AS OF 4:45 AM PDT WEDNESDAY...HIGH CLOUDS WILL CONTINUE
TO STREAM ACROSS THE REGION FROM NORTH TO SOUTH THIS MORNING. A FEW
PATCHES OF STRATUS PERSIST ALONG THE COAST AT THIS HOUR AN MAY
BRING TEMPORARY CIGS TO KMRY AND KSNS THIS MORNING. WINDS WILL BE
THE MAIN ISSUE OF THE DAY WITH BREEZY CONDITIONS LASTING MOST OF THE
DAY. KSFO WILL AGAIN SEE THE STRONGEST WINDS WITH SUSTAINED SPEEDS
OF 20 TO 28 KT AND GUSTS TO 34 KT. OTHERWISE...VFR CONDITIONS WILL
PREVAIL THROUGH THE FORECAST PERIOD.

&&

.MARINE..AS OF 4:45 AM WEDNESDAY...PLEASE NOTE THE MARINE ZONES
CHANGE AT 5 AM WEDNESDAY MORNING WITH THE NEAR SHORE ZONES NOW
COVERING 0-10 NM OFFSHORE AND THE OUTER ZONES COVERING 10-60 NM
OFFSHORE. UGC CODES REMAIN UNCHANGED. PLEASE SEE MAPS AND PUBLIC
INFORMATION STATEMENT OFF WEBSITE FOR MORE INFO.

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDA...SCA...ALL COASTAL WATERS.

PUBLIC FORECAST: SSA
AVIATION/MARINE: CW

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO