FXUS66 KMTR 040552
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
950 PM PST THU DEC 3 2009

.DISCUSSION...AS OF 8:50 PM PST THURSDAY...TEMPERATURES TODAY WERE
MOSTLY SIMILAR TO THOSE ON WEDNESDAY WITH HIGHS RANGING FROM THE
UPPER 40S TO UPPER 60S ACROSS THE DISTRICT...WITH HIGH ELEVATION
LOCATIONS COOLER THAN YESTERDAY AND INLAND LOWER ELEVATIONS SPOTS
WARMER BY A FEW DEGREES. SATELLITE IMAGERY SHOWS LOW CLOUDS AND FOG
ALREADY FORMING ACROSS INTERIOR SECTIONS OF THE NORTH AND EAST BAY...
AND SURFACE OBSERVATIONS SUBSTANTIATE THIS WITH SANTA ROSA AIRPORT
ALREADY REPORTING A HALF MILE IN FOG. EXPECT THE AREAL COVERAGE OF
LOW CLOUDS AND FOG TO EXPAND OVERNIGHT...ALTHOUGH THE MARINE LAYER IS
FAIRLY SHALLOW WITH THE INVERSION DEPTH AT AROUND 1000 FEET.

HIGH PRESSURE ALOFT OVER THE COAST WILL KEEP DRY WEATHER IN THE
FORECAST THROUGH TOMORROW AND MUCH OF THE COMING WEEKEND. BY SATURDAY
NIGHT THE UPPER RIDGE IS PROGGED TO SLIDE WESTWARD MAKING ROOM FOR AN
UPPER TROUGH TO DIG SOUTHWARD INTO THE PACIFIC NORTHWEST AND THEN
EAST INTO THE GREAT BASIN BY SUNDAY. LATEST MODEL RUNS INDICATE RAIN
CHANCES REACHING THE NORTH BAY SUNDAY EVENING AS A FRONT ASSOCIATED
WITH THE UPPER LOW CENTER MOVES ACROSS NORTHERN CALIFORNIA. THE 00Z
NAM BRINGS THE FRONT ACROSS THE BAY AREA AND INTO SOUTHWARD INTO
SANTA CRUZ BY MONDAY MORNING. THE 00Z GFS THEN KEEPS SHOWERS ACROSS
THE DISTRICT INTO MONDAY...DECREASING FROM NORTH TO SOUTH DURING THE
DAY. BY TUESDAY...A SHARP RIDGE ALONG THE WEST COAST IS FORECAST TO
KEEP THE STATE DRY. BY MIDWEEK...HOWEVER...A SWATH OF PACIFIC
MOISTURE IS FORECAST TO SPREAD ACROSS CENTRAL CALIFORNIA. THE GFS
KEEPS RAIN OR SHOWERS ACROSS THE DISTRICT THROUGH FRIDAY WHEN THE
UPPER LOW FINALLY MOVES INLAND. THE 12Z ECMWF FEATURES A SIMILAR
SOLUTION WITH RAINY PERIODS THROUGHOUT NEXT WEEK. CURRENT FORECASTS
ON TRACK WITH LATEST MODEL GUIDANCE SO NO UPDATES NEEDED AT THIS
TIME.

&&

.AVIATION...AS OF 9:50 PM PST THURSDAY...VLIFR CONDITION CURRENTLY
OVER KSTS WHILE VFR CONDITIONS EXIST ELSEWHERE. SATELLITE IMAGERY
SHOWS LOW CLOUDS ALREADY BEGINNING TO DEVELOP OVER THE SF BAY AND
OVER COASTAL VALLEYS. ANTICIPATE A NIGHT VERY SIMILAR TO LAST NIGHT
WITH IFR CIGS AND LOCAL IFR VSBYS OVERNIGHT. LIGHT WINDS WILL TURN
OFFSHORE OVERNIGHT.

VICINITY OF KSFO...VFR CONDITIONS EXPECTED TO DEVELOP IFR CIGS
BETWEEN 06Z-08Z TONIGHT. LOW CIGS WILL LIKELY CLEAR BY 16Z OR 17Z
FRIDAY MORNING. LIGHT OFFSHORE WINDS EXPECTED OVERNIGHT. WINDS WILL
VEER TO THE NW AFTER 22Z FRIDAY.

KSFO BRIDGE APPROACH...IFR CIGS DEVELOPING AT POST TIME. LOW CIGS
EXPECTED TO CLEAR AROUND 16Z FRIDAY MORNING.

MRY BAY AREA TERMINALS...IFR CIGS DEVELOPING OVER THE SALINAS VALLEY
AT POST TIME. EXPECTED IFR CIGS TO AFFECT KMRY AND KSNS BETWEEN 06Z-
08Z. LOW CIGS WILL LIKELY CLEAR BY 16Z-17Z FRIDAY MORNING.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
    .NONE

$$

PUBLIC FORECAST: SSA
AVIATION/MARINE: CW

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO