FXUS66 KMTR 250006
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
400 PM PST THU DEC 24 2009

.DISCUSSION...AS OF 2:00 PM PST THURSDAY...SKIES ARE SUNNY ACROSS THE
DISTRICT WITH TEMPS IN THE 50S AND 60S. WITH A RIDGE OVER THE WEST
COAST EXPECT DRY WEATHER THROUGH FRIDAY. THERE COULD BE SOME FOG
TONIGHT IN THE VALLEYS AS DEW PTS ARE AS MUCH AS 12 DEGREES HIGHER
(IN CONCORD). OVERNIGHT TEMPS TONIGHT SHOULD BE SIMILAR TO LAST NIGHT
AND DAYTIME HIGHS ON CHRISTMAS WILL BE SIMILAR TO TODAY.

MODELS CONTINUE TO HAVE A DIFFICULT TIME FOR THE WEEKEND AND THE
UPCOMING WEEK. MODELS HAVE A SHORTWAVE EJECTING FROM THE MAIN GULF OF
ALASKA LOW...AND MOVING IT TO THE COAST. THIS SHORTWAVE THEN SHEARS
INTO TWO PIECES...WITH THE 12Z MODELS MOVING THE STRONGEST PIECE
MOVING SOUTH OFF THE COAST AND INTO SOCAL. THE 18Z GFS FOLLOWS THIS
TREND...WHEREAS THE 18Z NAM12 NOW KEEPS A MORE INTACT SHORTWAVE. WITH
THE STRONG RIDGE OVER THE COAST HAVE TENDED TO GO WITH THE WEAKER
GFS/ECMWF SOLUTION IN SHEARING APART THE SHORTWAVE...LEAVING ONLY A
CHANCE OF RAIN FOR THE DISTRICT SAT AFTN THROUGH SUNDAY. ANY RAINFALL
SHOULD BE LIGHT.

NEXT WEEK LOOKS GENERALLY UNSETTLED. THERE COULD BE A CHANCE OF
SHOWERS EACH DAY...BUT IT SHOULD NOT BE A WASHOUT. ADDITIONALLY...ANY
RAINFALL WILL BE LIGHT. ON MONDAY ANOTHER SPLITTING SHORTWAVE DIVES
INTO THE DESERT SW. BY TUESDAY A WEAK SHORTWAVE WILL RIDE INTO
NORTHERN AND CENTRAL CALIFORNIA. WEDNESDAY COULD BE THE DRIEST OF THE
DAYS AS A WEAK RIDGE MOVES BACK OVER THE COAST. ANOTHER SHORTWAVE
MOVES TO THE PACIFIC NW AND NORTHERN CA COAST ON THURSDAY FOR ANOTHER
CHANCE OF SHOWERS...WITH THE DISTRICT BEING ON THE SOUTHERN END OF
THE PRECIPITATION. GFS ENSEMBLES CONTINUE TO SHOW A WIDE VARIETY OF
SOLUTIONS...WITH MOST SHOWING A NW FLOW WITH A RIDGE OFF THE COAST...
NOT A BIG RAIN PRODUCING PATTERN FOR THE DISTRICT.

&&

.AVIATION...AS OF 4:00 PM THURSDAY...

HIGH PRESSURE OVER THE GREAT BASIN WILL MAINTAIN LIGHT OFFSHORE
FLOW AND A DRY LOW LEVEL AIR MASS OVER THE DISTRICT TONIGHT AND
FRIDAY. WITH THE EXCEPTION OF KSTS...VFR CONDITIONS ARE EXPECTED TO
PREVAIL AT ALL TERMINALS THROUGH CHRISTMAS DAY. AT KSTS...FOG
OR FREEZING FOG IS EXPECTED TO REDEVELOP LATE THIS EVENING AND
PERSIST INTO THE MORNING.

VICINITY OF KSFO...VFR CONDITIONS THROUGH CHRISTMAS DAY. WINDS WILL
BE GENERALLY EAST TO NORTHEAST AROUND 5 KT THROUGH FRIDAY MORNING...
AND THEN TURN WEAKLY ONSHORE AT TIMES IN THE AFTERNOON.

KSFO BRIDGE APPROACH...SAME AS KSFO.

MRY BAY AREA TERMINALS...VFR CONDITIONS THROUGH CHRISTMAS DAY.
LIGHT EASTERLY WINDS WILL SWITCH TO LIGHT NORTHWESTERLY DURING THE
AFTERNOON ON FRIDAY.

&&

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

$$

PUBLIC FORECAST: MHS
AVIATION/MARINE: LARRY/BLIER

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO