SFOAFDMTR (05/14/13 0445)

FXUS66 KMTR 141149
AFDMTR

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

.DISCUSSION...AS OF 4:17 AM PDT TUESDAY...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 4:45 AM PDT TUESDAY...MARINE LAYER HAD MIXED OUT
LAST NIGHT BUT IS STARTING TO REFORM. STRATUS IS INCREASING ALONG
THE COAST WITH AREAS OF STRATUS SPREADING ACROSS THE CITY OF SAN
FRANCISCO INTO THE EAST BAY. OAK IS IN THE STRATUS DECK WHILE SFO
IS ON THE SOUTHERN EDGE. SFO WILL HAVE IN AND OUT MVFR CIGS
THROUGH 17Z.

VICINITY OF KSFO...OCCASIONAL MVFR CIGS THROUGH 16-17Z. WEST WIND
GUSTS TO 25 KNOTS AFTER 20Z.

KSFO BRIDGE APPROACH...MVFR CIGS NEAR SFO THROUGH 16-17Z. THE
SOUTHERN PART OF THE APPROACH REMAINS VFR.

MONTEREY BAY AREA TERMINALS...MVFR CIGS THROUGH 18-19Z.

&&

.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: RWW
AVIATION/MARINE: W PI

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