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000
FXUS66 KMTR 171039
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
339 AM PDT FRI MAY 17 2013

.DISCUSSION...AS OF 3:38 AM PDT FRIDAY...AN UPPER LEVEL TROUGH
CURRENTLY MOVING ACROSS THE DISTRICT HAS SCOURED OUT MOST OF THE
LOW CLOUDS ACROSS THE REGION. PATCHY CLOUDS REMAIN ANCHORED OVER
THE HILLS OF THE EAST BAY...SANTA CRUZ MOUNTAINS AND NORTHERN
MONTEREY AND SAN BENITO COUNTIES AS A RESULT OF LOW LEVEL
MOISTURE LEFT OVER FROM THE SCATTERED LIGHT RAIN THAT FELL ACROSS
THE AREA THURSDAY. LOW CLOUDS MAY EXPAND IN COVERAGE LATER THIS
MORNING BUT ARE EXPECTED TO CLEAR BY MIDDAY MAKING WAY FOR MOSTLY
CLEAR SKIES.

TEMPERATURES ARE FORECAST TO RUN SLIGHTLY BELOW NORMAL TODAY AS
A COOLER AIRMASS SETTLES IN OVER THE REGION AND COOL MARINE AIR
FILTERS IN AS A RESULT OF A MODERATE ONSHORE GRADIENT. WARMER
TEMPERATURES ARE FORECAST SATURDAY AS HIGH PRESSURE BUILDS AT THE
SURFACE AND ALOFT. THE GRADUAL WARMING TREND IS EXPECTED TO
PERSIST THROUGH MONDAY. SLIGHTLY ABOVE NORMAL TEMPERATURES ARE IN
STORE SUNDAY AND MONDAY WITH TEMPERATURES EXPECTED TO PEAK ON
MONDAY.

THE MARINE LAYER IS EXPECTED TO REESTABLISH ITSELF LATE TONIGHT
INTO SATURDAY WITH A DEPTH OF AROUND 1500 FEET OR LESS. HIGH
PRESSURE OVER THE REGION WILL LIKELY KEEP THE MARINE LAYER
RELATIVELY SHALLOW INTO EARLY NEXT WEEK.

MODELS INDICATE THE HIGH OVER THE EASTERN PACIFIC WILL RIDGE
ACROSS THE PACIFIC NORTHWEST AND INTO THE GREAT BASIN ON SUNDAY
CAUSING WINDS TO TURN NORTHERLY WITH A SLIGHT OFFSHORE COMPONENT.
AT THE SAME TIME A SHORTWAVE TROUGH SLIDING IN ALOFT OVER THE GREAT
BASIN WILL CAUSE WINDS TO STRENGTHEN ESPECIALLY OVER THE HILLS OF
THE NORTH AND EAST BAY. 925 MB WINDS SHOW WINDS AROUND 25 TO 30
KTS SUNDAY EVENING INTO MONDAY.

AS TEMPERATURES WARM SUNDAY INTO MONDAY AND DRY NORTHERLY WINDS
STRENGTHEN FIRE WEATHER CONCERNS WILL INCREASE. RED FLAG WARNINGS
ARE NOT EXPECTED AT THIS TIME DUE TO THE SHORT DURATION AND
STRENGTH OF THE WIND EVENT. HOWEVER CONDITIONS WILL NEED TO BE
MONITORED CLOSELY.

ON THE BRIGHT SIDE...SKIES SHOULD CLEAR NICELY MONDAY MAKING WAY
FOR A BEAUTIFULLY SUNNY DAY WITH TEMPERATURES WELL ABOVE NORMAL.
TEMPERATURES WILL RISE INTO THE 70S ALONG THE COAST WITH 80S TO
LOWER 90S INLAND. WARMEST INLAND LOCATIONS WILL SEE TEMPS RISE
INTO THE UPPER 90S WITH A FEW SITES POSSIBLY REACHING THE CENTURY
MARK.

BUT AS THEY SAY ALL GOOD THINGS MUST COME TO AND END AND SO SHALL
THIS WARMING TREND. MODELS SHOW AN UPPER LEVEL TROUGH MOVING IN
FROM THE NORTH BRINGING IN A SIGNIFICANTLY COOLER AIRMASS WHICH IS
EXPECTED TO COOL TEMPERATURES ACROSS THE REGION. TEMPERATURES WILL
SEE THE GREATEST DROP DURING THE SECOND HALF OF THE WEEK AS THE
LOW SLIDES SOUTH ACROSS THE FORECAST AREA. THE NORTH BAY MAY SEE
PRECIP FROM THIS SYSTEM HOWEVER WILL CONTINUE TO WATCH TO SEE HOW
THIS SYSTEM DEVELOPS BEFORE NAILING DOWN THE TIMING OR COVERAGE.

&&

.AVIATION...AS OF 10:55 PM PDT THURSDAY...INTERESTING EVOLUTION TO
COASTAL STRATUS THIS EVENING AS STARTED TO COME IN EARLY...THEN
CLEARED BACK TO NEAR COAST...AND NOW REDEVELOPING AND MORE
ROBUSTLY BEGINNING TO EXPAND INLAND. CIGS CURRENTLY EXIST AT BOTH MRY
BAY TERMINALS AND KSFO...AND ARE EXPECTED TO DEVELOP AT REMAINING
TERMINALS WITHIN THE NEXT COUPLE OF HOURS. CONTINUE TO EXPECT LOW
CLOUD COVERAGE TO BE WIDESPREAD BY MORNING...BUT NEW 00Z NAM MODEL
MOS GUIDANCE AND KSFO BUFR SOUNDING SUGGEST CLEARING ON FRIDAY A
BIT EARLIER THAN PREVIOUS THINKING AND HAVE MADE SOME
CORRESPONDING ADJUSTMENTS TO THE TAFS.

VICINITY OF KSFO...EXPECT MVFR CIGS TO CONTINUE THROUGH THE NIGHT
AND INTO FRIDAY MORNING. HAVE MOVED UP CLEARING TIME ON FRIDAY A
BIT FROM PREVIOUS TAF...BUT CONFIDENCE IS LOW. ONSHORE FLOW LOOKS
TO REDEVELOP FRIDAY AFTERNOON SIMILAR TO TODAY.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...IFR CIGS AT KMRY EXPECTED TO CONTINUE
THROUGH THE NIGHT...WITH SOME POSSIBILITY OF LOWERING TO LIFR.
KSNS MVFR CIGS WILL SIMILARLY CONTINUE...WITH CHANCE OF LOWERING TO
IFR. CURRENT INDICATIONS ARE THAT CLEARING ON FRIDAY WILL OCCUR
AROUND MIDDAY...A BIT EARLIER AT KSNS THAN KMRY...BUT COULD BE
DELAYED INTO THE EARLY AFTERNOON AT THE LATTER.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT REYES TO PIGEON PT 0-10 NM FROM 3 PM
             SCA...PT ARENA TO PIGEON PT 10-60 NM FROM 3 PM
             SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM FROM 3 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...PT ARENA TO PT REYES 0-10 NM FROM 9 AM
             SCA...SF BAY FROM 1 PM

&&

$$

PUBLIC FORECAST: CW
AVIATION/MARINE: BLIER

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