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000
FXUS66 KMTR 141735
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1035 AM PDT TUE MAY 14 2013

.DISCUSSION...AS OF 9:25 AM PDT TUESDAY...A NEARLY 6 MB NORTHERLY
GRADIENT HELPED TO KEEP MOST OF SF BAY AREA CLOUD FREE THIS
MORNING WHILE A LARGE A CHUNK OF THE MONTEREY BAY AREA REMAINS
SOCKED IN. TEMPERATURES ARE RUNNING CLOSE TO WHERE THEY WERE
YESTERDAY (ALTHOUGH SANTA ROSA IS 11 AHEAD DUE TO SUNNY CONDITIONS
-- RH VALUES DOWN AROUND 35%).

EXPECT HIGHS TODAY A FEW DEGREES COOLER THAN YESTERDAY AS THE
WESTERLY SURFACE FLOW HAS INCREASED 1 MB WHILE THE MARINE LAYER
HAS JUMPED FROM AROUND 1,200 FEET TO AROUND 2,500 FEET RIGHT NOW.
MOST COASTAL HIGHS WILL BE IN THE 60S WITH UPPER 70S TO MID 80S
FOR MOST INLAND SPOTS.

NO WEATHER HEADLINES EXPECTED FOR THE REST OF THE WORK WEEK.
TEMPERATURES WILL LOWER AS THE ZONAL FLOW SWITCHES TO A COOLER
PATTERN AS A LONGWAVE TROF MOVES OVERHEAD. WARMER WEATHER RETURNS
JUST IN TIME FOR THE WEEKEND (ESPECIALLY ON SUNDAY) AS A RIDGE OF HIGH
PRESSURE BUILDS BACK TO THE SW CONUS.

PREVIOUS DISCUSSION...MARINE LAYER IS FINALLY SHOWING SIGNS OF
DEEPENING IN RESPONSE TO UPPER TROUGH PASSING OVERHEAD. FORT ORD
PROFILER AND SAN CARLOS SODAR SHOW THE DEPTH NOW AROUND 2000 FEET.
INTERESTINGLY ENOUGH A 7 MB NORTHERLY GRADIENT RAMPED UP AROUND
00Z LAST NIGHT AND HAS MAINTAINED ITSELF. BELIEVE THAT FEATURE IS
LARGELY RESPONSIBLE FOR THE LACK OF STRATUS AS FOG PRODUCT SHOWS
NO STRATUS NORTH OF THE GOLDEN GATE AND ONLY PATCHY COVERAGE
INSIDE THE BAY THIS MORNING.

WATER VAPOR SHOWS A WELL DEFINED...ALMOST PICTURESQUE UPPER LEVEL
LOW PASSING RIGHT OVER THE BAY AREA AT THIS HOUR WITH A CLEARLY
DEFINED CIRCULATION AT UPPER LEVELS. HOWEVER...OUTSIDE OF
DEEPENING THE MARINE LAYER NOT TOO MUCH IMPACT AT THE SURFACE.
A CIRCULATION THAT WELL DEFINED ALWAYS GIVES ONE PAUSE FOR BUST
POTENTIAL BUT ALL MODELS ARE ADAMANT THAT NO PRECIP WILL DEVELOP
OVER OUR DISTRICT. HOWEVER SOME CONVECTIVE ACTIVITY WILL TRIGGER
OVER THE SOUTHERN SIERRA THIS AFTERNOON IN ASSOCIATION WITH THE
VORT MAX.

FOR THE BAY AREA...ONSHORE FLOW AND COOLING ALOFT WILL KEEP ANY
HOT WEATHER IN CHECK WITH SEASONABLE SPRING TEMPERATURES RUNNING
FROM THE 60S COAST...70S BAYSIDE AND 80S INTERIOR VALLEYS. NOT TOO
MUCH CHANGE FORECAST FOR WEDS BUT ALL THE VARIOUS MOS GUIDANCE
WANTS TO SHOW A COOLING TREND OF A FEW DEGREES FOR WEDS AFTERNOON.

BY THURSDAY A COOL TROUGH WILL MOVE INTO THE PACIFIC NORTHWEST AND
FAR NORTHERN CALIFORNIA. SHOWER CHANCES WILL SKIRT DOWN INTO
MENDOCINO COUNTY BUT NOT EXPECTING ANYTHING TO REACH THE NORTH
BAY. MUCH COOLER AIR ALOFT WILL PROMOTE MIXING OUT OF ANY MARINE
CLOUDS WITH 850 MB TEMPS DOWN TO 5 OR 6 CELSIUS...MUCH COOLER THAN
THE OCEAN SST.

THE TROUGH AXIS WILL SHIFT EAST BY FRIDAY AND THE ONSET OF A
WARMING TREND WILL ENSUE WITH SEASONABLE TEMPERATURES FORECAST SATURDAY.
IF THE ECMWF IS RIGHT A MORE PRONOUNCED WARMING TREND WILL BE FELT
BY SUNDAY AND MONDAY WITH WIDESPREAD READINGS INTO THE 80S AND
LOWER 90S WITH EVEN 70S BY THE COAST. WILL HAVE TO WATCH FOR THE
COMBINATION OF WELL ABOVE NORMAL TEMPERATURES...STRONG NORTHERLY
WINDS AND THE IMPACT ON FIRE WEATHER ACROSS MUCH OF THE STATE
AGAIN BY SUNDAY/MONDAY TIME FRAME.

&&

.AVIATION...AS OF 10:35 AM PDT TUESDAY...AS MENTIONED ABOVE THE
NORTHERLY GRADIENT IS KEEPING THE MAJOR THREE AIRPORTS VFR THIS
MORNING WITH MONTEREY BAY KEEPING CIGS IN PLACE. SOME ONSHORE FLOW
TONIGHT WILL ALLOW FOR PATCHY CIGS AROUND SAN FRANCISCO BAY AND
MORE WIDESPREAD CIGS AROUND MONTEREY BAY. KSTS WILL BE MAINLY VFR
AND THE SAME WITH KSJC. GUSTY WINDS POSSIBLE AGAIN THIS AFTERNOON
IN SAN FRANCISCO BAY.


VICINITY OF KSFO...MAINLY VFR THROUGH THE PERIOD. A FEW CIGS
POSSIBLE TONIGHT FOR KSFO...BUT BETTER CHANCE FOR KOAK. SIMILAR
SCENARIO AS THIS MORNING. GUSTS UP TO 30 KT POSSIBLE FOR KSFO THIS AFTERNOON.

KSFO BRIDGE APPROACH...SIMILAR TO SFO.

MONTEREY BAY AREA TERMINALS...MVFR CIGS THROUGH 18-19Z THEN VFR
THIS AFTERNOON. CIGS RETURN EARLY AGAIN TONIGHT.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...SF BAY FROM 1 PM
             SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 1 PM
             SCA...PT ARENA TO PT REYES 0-10 NM
             SCA...PT REYES TO PIGEON PT 0-10 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...PT ARENA TO PIGEON PT 10-60 NM
             SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM

&&

$$

PUBLIC FORECAST: BELL/RWW
AVIATION/MARINE: MM

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