FXUS66 KMTR 010504
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
904 PM PST MON NOV 30 2009

.DISCUSSION...AS OF 9:00 PM PST MONDAY...THE MAIN FOCUS IS THE MAJOR
PATTERN CHANGE...WHICH MAY DEVELOP BY THE END OF THE UPCOMING
WEEKEND.

AFTER A COOL START THIS MORNING (ESPECIALLY IN THE VALLEYS)...
TEMPERATURES WARMED NICELY UNDER SUNNY SKIES. AFTERNOON HIGHS
ENDED UP AT LEAST A FEW DEGREES ABOVE NORMAL. PATCHY LOW CLOUDS AND
FOG HAVE DEVELOPED AT THE COAST NORTH OF POINT REYES THIS EVENING.
WITH LIGHT OFFSHORE FLOW IN PLACE...BELIEVE THERE WON'T BE MUCH MORE
DEVELOPMENT OF COASTAL LOW CLOUDS AND FOG OVERNIGHT...AND CERTAINLY
NOT AN INLAND PUSH. SURFACE DEWPOINTS THIS EVENING ARE SEVERAL
DEGREES HIGHER THAN AT THIS TIME LAST EVENING AND SO TEMPERATURES
TONIGHT ARE NOT EXPECTED TO DROP AS LOW AS LAST NIGHT. WITH HIGHER
DEWPOINTS...PATCHY RADIATION FOG IS LIKELY IN THE VALLEYS BY
MORNING...PARTICULARLY IN THE NORTH BAY VALLEYS.

NOT MUCH CHANGE IS EXPECTED IN OUR WEATHER THROUGH THE REMAINDER
OF THE WORK WEEK AS A HIGH AMPLITUDE UPPER RIDGE REMAINS IN PLACE
ALONG THE WEST COAST OF NORTH AMERICA.

THE MODELS ARE IN GENERAL AGREEMENT REGARDING THE DEVELOPMENT OF A
WET PATTERN BY THE MIDDLE OF NEXT WEEK. THE UPPER RIDGE IS FORECAST
TO AMPLIFY NORTHWARD INTO ALASKA BY SUNDAY. MEANWHILE...MOISTURE AND
ENERGY FROM WESTERN PACIFIC TYPHOON NIDA WILL BECOME ENTRAINED IN
THE WESTERLIES...STRENGTHENING AND EXTENDING THE EAST ASIAN JET
ACROSS THE PACIFIC...AND PROVIDING ENOUGH POWER TO UNDERCUT THE
RIDGE AND SEND A SIGNIFICANT AMOUNT OF MOISTURE INTO CALIFORNIA.
HOWEVER...THERE IS DISAGREEMENT ON HOW SOON THE UNDERCUTTING WILL
OCCUR. THE 12Z ECMWF DEVELOPS A MAJOR PRECIP EVENT ACROSS NEARLY THE
ENTIRE STATE OF CALIFORNIA FROM LATE SUNDAY THROUGH MONDAY. THE 00Z
GFS..ON THE OTHER HAND...HOLDS OFF WITH THE INITIAL SALVO OF RAIN AND
WIND UNTIL THE MIDDLE OF NEXT WEEK...WITH MORE RAIN FORECAST TO
QUICKLY FOLLOW. THE MESSAGE AT THIS POINT IS THIS: CONFIDENCE IS HIGH
REGARDING THE UPCOMING MAJOR PATTERN CHANGE AND THE POTENTIAL FOR AN
EXTENDED PERIOD OF WET WEATHER. BUT THE TIMING REMAINS UNCERTAIN...
ESPECIALLY FOR THE INITIAL EVENT. FOR PLANNING PURPOSES...POTENTIALLY
HEAVY RAINFALL AND STRONG WINDS MAY ARRIVE AS EARLY AS SUNDAY
NIGHT...OR AS LATE AS THE MIDDLE OF NEXT WEEK. AND...WET AND BLUSTERY
WEATHER WILL LIKELY PERSIST OFF AND ON FOR SEVERAL DAYS ONCE IT
STARTS. HAZARDOUS WEATHER OUTLOOKS/SPECIAL WEATHER STATEMENTS WILL BE
ISSUED ONCE THERE IS A CLEARER IDEA ON THE TIMING.

&&

.AVIATION...AS OF 8:55 PM PST MONDAY...HIGH PRESSURE OVER THE REGION
WILL MAINTAIN MOSTLY CLEAR SKIES AND LIGHT OFFSHORE FLOW OVER THE
TERMINALS THROUGH THE NEXT 30 HOURS. EXPECT PATCHY GROUND FOG TO
DEVELOP LATE TONIGHT AFTER 10Z NEAR KSTS.

VICINITY OF KSFO...VFR CONDITIONS WITH CLEAR SKIES AND LIGHT
AND VARIABLE WINDS EXPECTED THROUGH TUESDAY.

KSFO BRIDGE APPROACH...SAME AS KSFO.

MRY BAY AREA TERMINALS...VFR CONDITIONS UNDER CLEAR SKIES EXPECTED
THROUGH TUESDAY. LIGHT EAST WINDS EXPECTED TO CONTINUE THROUGH THE
NIGHT.

&&

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

$$

PUBLIC FORECAST: DYKEMA
AVIATION/MARINE: CW

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO