000
FXUS66 KMTR 201750
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1050 AM PDT MON MAY 20 2013

...CONTINUED SUNNY AND WARM TODAY...
...MUCH COOLER WITH BREEZY ONSHORE WINDS TUESDAY...

.DISCUSSION...AS OF 9:37 AM PDT MONDAY...NO FORECAST UPDATES
PLANNED FOR THIS MORNING. SKIES ARE CLEAR ACROSS THE ENTIRE BAY
AREA THIS MORNING AND TEMPERATURES WILL QUICKLY WARM WITH 850 MB
TEMPS MEASURED AT 16 CELSIUS ON THE 12Z KOAK SOUNDING AND AS WARM
AS 20 CELSIUS AT 900 MB. THE NORTHERLY GRADIENT DOWN THE COAST IS
6 MB WITH THE LARGE SCALE OFFSHORE GRADIENT FROM THE GREAT BASIN
BACK TO THE COAST AROUND 7 MB WHILE THE LOCAL SFO-SAC IS AROUND 1
MB ONSHORE. 24 HOUR TRENDS ARE ALREADY RUNNING 3-8 DEGREES WARMER
THAN YESTERDAY AFTER NORTHERLY BOUNDARY LAYER WINDS IN THE HILLS
KEPT OVERNIGHT LOWS RELATIVELY MILD. EXPECT WARM TO HOT WEATHER
TODAY WITH 70S AT THE BEACHES...80S INTO THE BAY AND 90S FOR THE
INLAND VALLEYS.

UPPER LEVEL TROUGH OF INTEREST THAT WILL INDUCE COOLING TREND
BEGINNING TOMORROW SHOWS UP NICELY ON WATER VAPOR JUST APPROACHING
45N/130W. THIS COLD CORE LOW WILL QUICKLY DROP TOWARDS FAR
NORTHERN CALIFORNIA/OREGON BORDER BY EARLY TUESDAY MORNING. 850 MB
TEMPS WILL PLUMMET...DROPPING TO AROUND 5-6 CELSIUS ACROSS
NORTHERN SONOMA COUNTY BY TUESDAY AFTERNOON. GUSTY ONSHORE WINDS
WILL KEEP TEMPERATURES IN THE UPPER 50S AT THE BEACHES...60S
INSIDE THE BAY AND ONLY 70S FOR THE INLAND VALLEYS OF THE BAY
AREA. ONLY THE FAR SOUTHERN SALINAS VALLEY WILL HOLD ONTO HOT
WEATHER FOR TUESDAY AFTERNOON. IN ADDITION TO THE COOLING TREND
THE GUSTY ONSHORE WINDS WILL BE MOST NOTICEABLE ALONG THE COAST
AND INTO THE WIND PRONE COASTAL GAPS AS WELL AS PLACES LIKE KSFO.
MODEL GUIDANCE INDICATES THE PERIOD OF STRONGEST WINDS WILL BE
TUESDAY AFTERNOON AND EVENING WHEN GUSTS TO AROUND 40 MPH WILL BE
MOSTLY LIKELY FOR PLACES LIKE KSFO AND POINT REYES.

WINDS WILL GRADUALLY EASE INTO WEDS MORNING. HOWEVER THE MAIN
UPPER LOW WILL STAY OVER THE WEST COAST. THE COMBINATION OF
ONSHORE WINDS AND COOL TEMPS ALOFT SHOULD KEEP MARINE CLOUDS TO A
MINIMUM IF AT ALL. EXPECT SUNNY AND SEASONABLY PLEASANT WEATHER
WITH AFTERNOON HIGHS IN THE 60S ALONG THE COAST WITH 70S FOR MOST
INLAND LOCATIONS WHICH IS A FEW DEGREES BELOW NORMAL FOR THE
SECOND HALF OF MAY. ONLY THE WARMEST INTERIOR SPOTS SHOULD REACH
THE 80S DURING THE AFTERNOON HOURS LATER THIS WEEK.

NO BIG CHANGES FORECAST RIGHT INTO THE WEEKEND WITH NEAR OR
SLIGHTLY BELOW NORMAL TEMPERATURES AND CONTINUED DRY WEATHER.

&&

.AVIATION...AS OF 10:50 AM PDT MONDAY...LIGHT OFFSHORE FLOW
THROUGH MIDDAY WILL MAINTAIN VFR CONDITIONS UNDER CLEAR SKIES
THROUGH MONDAY EVENING. A LIGHT TO MODERATE AFTERNOON SEABREEZE
WILL DEVELOP...BUT MARINE LAYER CLOUDS ARE NOT EXPECTED TO FORM
UNTIL LATE MONDAY NIGHT. MVFR/IFR CIGS POSSIBLE AFTER 10Z MONDAY
NIGHT...CONTINUING UNTIL 15-16Z TUESDAY MORNING. WEST TO NORTHWEST
WINDS WILL BEGIN TO INCREASE LATE MONDAY NIGHT AND CONTINUE TO
INCREASE THROUGH TUESDAY AFTERNOON. LOCALLY STRONG AND GUSTY WINDS
EXPECTED FROM MID AFTERNOON TUESDAY THROUGH TUESDAY EVENING.

VICINITY OF KSFO...VFR CONDITIONS THROUGH AT LEAST LATE MONDAY
EVENING. WEST WINDS WILL INCREASE TO 18G23 KNOTS BY MID AFTERNOON
AND THEN GRADUALLY DECREASE DURING THE EVENING. MVFR/IFR CIGS
POSSIBLE LATE TONIGHT...BY 12Z...CONTINUING UNTIL ABOUT 16Z
TUESDAY MORNING. CONFIDENCE MODERATE. WESTERLY WINDS WILL BEGIN TO
INCREASE LATE TONIGHT AND BECOME STRONG AND GUSTY BY MID AFTERNOON
TUESDAY...25G32 KNOTS. AN AIRPORT WEATHER WARNING FOR GUSTS OF AT
LEAST 35 KNOTS MAY BE NEEDED FOR TUESDAY AFTERNOON AND EVENING.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO EXCEPT LESS LIKELY TO SEE
LOW CIGS LATE TONIGHT/TUESDAY MORNING.

MONTEREY BAY AREA TERMINALS...VFR CONDITIONS THROUGH AT LEAST LATE
MONDAY EVENING. IFR CIGS LIKELY TO FORM SOMETIME BETWEEN 10Z AND
12Z AND CONTINUE UNTIL ABOUT 16Z TUESDAY MORNING. INCREASING
WESTERLY WINDS ON TUESDAY WITH AFTERNOON GUSTS TO 25 KNOTS.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM

&&

$$

PUBLIC FORECAST: RWW
AVIATION/MARINE: DYKEMA

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