FXUS66 KMTR 261234
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
408 AM PST SAT DEC 26 2009

.DISCUSSION...AS OF 3:50 AM PST SATURDAY...CLOUDS ARE INCREASING
ACROSS THE DISTRICT AS A COLD FRONT APPROACHES THE COAST. HOWEVER...
THIS COLD FRONT IS STRETCHING AS IT BUMPS UP AGAINST THE RIDGE ALONG
THE COAST. AMSU IMAGERY IS INDC ABOUT ONE INCH OF TPW WITH THIS
FRONT. A VORT MAX IS CENTERED NEAR 40/137. THIS VORT IS QUITE
CONVECTIVE WITH SEVERAL LIGHTNING STRIKES NOTED BY THE EXPERIMENTAL
LONG RANGE LIGHTNING DETECTION SYSTEM. AMSU RAINRATES WITH THIS VORT
ARE AS MUCH AS .3 INCHES/HR. TEMPS THIS MORNING ARE IN THE 30S AND
40S...SEVERAL DEGREES WARMER THAN YESTERDAY MORNING...DUE TO THE
INCREASING CLOUD COVER.

AS THE FRONT MOVES TO THE COAST IT WILL CONTINUE TO WEAKEN. LIGHT
RAIN WILL MOVE TO THE DISTRICT BY AFTERNOON...RADAR IS INDC PLENTY OF
ELEVATED ECHOES OFF THE COAST...MOST LIKELY CLOUDS. ADDITIONALLY...
THE 00Z OAKLAND RAOB WAS QUITE DRY WITH ONLY 0.30 INCHES OF PW.
RAINFALL IS EXPECTED TO BE LIGHT WITH THIS FRONT. AS THE ASSOCIATED
TROUGH MOVES OVER THE COAST THE RAIN WILL BECOME MORE SHOWERY IN
NATURE. EVEN THOUGH THE MODIFIED SOUNDING FOR MONTEREY THIS EVENING
IS INDC A LI OF -0.5...WITH THE CONTINUED MODEL INCONSISTENCY AND
WITH THE VORT WEAKENING AND SPLITTING HAVE DECIDED NOT TO MENTION
THUNDER IN THE FCST. SHOWERS WILL DECREASE MONDAY AND MONDAY NIGHT
AS THE TROUGH SHIFTS TO THE EAST.

HAVE DECIDED NOT TO MAKE ANY MAJOR CHANGES TO THE EXTENDED DUE TO
CONTINUED MODEL INCONSISTENCY. IN GENERAL...A RIDGE WILL DEVELOP
JUST EAST OF 130W. SHORTWAVES WILL BE EJECTING FROM THE PARENT
TROUGH ALONG 150W AND WILL BE RIDING ALONG THE RIDGE BEFORE
DROPPING SE INTO THE CENTRAL PART OF THE COUNTRY. THIS WILL BRING A
CHANCE/SLIGHT CHANCE OF SHOWERS OFF AND ON FOR MAINLY THE NORTH BAY
FROM TUESDAY THROUGH NEW YEARS DAY. IT WON'T BE A WASHOUT THIS
UPCOMING WEEK...JUST UNSETTLED. THIS PATTERN IS NOT CONDUCIVE TO
ALOT OF RAIN FOR THE DISTRICT.

&&

.AVIATION...AS OF 4:30 AM SATURDAY...THE DAY AFTER CHRISTMAS...
SOUTHERLY FLOW WILL INCREASE DURING THE MORNING AS A FRONTAL
SYSTEM APPROACHES THE AREA. CURRENTLY HIGH CLOUDS OVER THE AREA
BUT EXPECT LOWER CEILINGS OF AROUND 5000 FEET INTO THE AREA AFTER
20S. SHOWERS WITH CEILINGS DOWN TO 3500 FEET WILL MOVE INTO THE NORTH
BAY AROUND 21Z AND SPREAD SOUTH TO THE MRY BAY AREA DURING THE
AFTERNOON. SOUTHEAST WINDS WILL PEAK AROUND 10 KT LATE AFTERNOON
THROUGH EARLY EVENING.

VICINITY OF KSFO...VFR CONDITIONS WITH HIGH CIRRUS CLOUDS
THROUGH THE MORNING. A CHANGE IS EXPECTED AFTER 20Z WITH LOWER
5000 FOOT CEILINGS MOVING OVER THE AIRPORT. SHOWERS WILL MOVE IN
AFTER 23Z WITH CEILINGS LOWERING TO AROUND 3500 FEET. SOUTHEAST
WINDS WILL BE 5 KT OR LESS THROUGH THE MORNING THEN INCREASE TO
8-10 KT IN THE AFTERNOON.

KSFO BRIDGE APPROACH...SAME AS KSFO.

MRY BAY AREA TERMINALS...VFR CONDITIONS WITH HIGH CIRRUS CLOUDS
THROUGH THE MORNING. A CHANGE IS EXPECTED AFTER 22Z WITH
LOWER 5000 FOOT CEILINGS MOVING INTO THE MRY BAY AREA. SCATTERED
SHOWERS WILL MOVE INTO THE AREA AFTER 00Z WITH CEILINGS LOWERING
TO AROUND 3000 FEET. LIGHT SOUTHEAST WINDS THROUGH THE DAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
   .TDY...SCA...PT ARENA TO PIGEON PT 10-60 NM STARTING 10 AM.
       ...SCA...PT ARENA TO PT REYES 0-10 NM STARTING THIS AFTERNOON.

$$

PUBLIC FORECAST: MHS
AVIATION/MARINE: W PI

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO