000
FXUS66 KMTR 202141
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
241 PM PDT MON MAY 20 2013

...MUCH COOLER WITH BREEZY ONSHORE WINDS TUESDAY...

.DISCUSSION...AS OF 2:41 PM PDT MONDAY...AFTER A SUNNY AND WARM
MONDAY THE FORECAST FOCUS WILL BE ON FAIRLY DRAMATIC COOLING TREND
TUESDAY WITH CONTINUED NEAR OR BELOW NORMAL TEMPERATURES THROUGH
THE WORK WEEK.

SHORT TERM...24 HOUR TEMPERATURE TRENDS SHOW MOST LOCATIONS
RUNNING 5 TO 10 DEGREES WARMER THAN SUNDAY AFTERNOON WITH MODERATE
NORTHERLY GRADIENT AND LIGHT ONSHORE WINDS. WINDS HAVE TURNED WEST
AT THE GOLDEN GATE AND KSFO SO THE SEA-BREEZE HAS INITIATED ALONG
THE COAST AFTER THE CITY REACHED A HIGH OF 79 EARLIER THIS AFTERNOON.
WELL DEFINED CIRCULATION CAN BE SEEN ON BOTH VISIBLE AND WATER
VAPOR IMAGERY CURRENTLY NEAR 45N/130W. AS NOTED THIS MORNING THIS
LOW WILL TRUDGE TOWARDS FAR NORTHERN CALIFORNIA BY TUESDAY MORNING.
MAIN IMPACT HERE WILL BE MUCH COOLER TEMPERATURES FOR TUESDAY
AFTERNOON ALONG WITH GUSTY ONSHORE WINDS. ON AVERAGE INLAND AREAS
SHOULD COOL AT LEAST 15 DEGREES FROM MONDAY AFTERNOON TO TUESDAY
AFTERNOON WITH SOME LOCATIONS OBSERVING 20 DEGREE DROP IN AFTERNOON
HIGHS. MODEL GUIDANCE SHOWS THAT GUSTY WEST WINDS WILL REALLY
PERSIST IN THE BAY ALL DAY LONG BUT OF COURSE BE STRONGEST DURING
THE AFTERNOON AND EVENING HOURS OF TUESDAY. THE COMBINATION OF
COOL ADVECTION AND INCREASING ONSHORE PRESSURE GRADIENTS WILL
INDUCE WINDY CONDITIONS ALONG THE COAST AND IN THE HILLS. HAVE
CONSIDERED WIND ADVISORIES BUT AS A WHOLE FEEL THAT ON AVERAGE
WE`LL KEEP WIDESPREAD WIND GUSTS BELOW 45 MPH EXCEPT FOR THE MOST
WIND PRONE LOCATIONS ALONG THE COAST AND IN THE HILLS ABOVE 2000 FEET.

AFTER THE SIGNIFICANT COOLING ON TUESDAY...TEMPERATURES WILL LEVEL
OFF WEDS WITH NO BIG CHANGES. EXPECT READINGS IN THE 60S COAST AND
BAY WITH ONLY MID 70S INLAND AREAS FOR WEDS. IN GENERAL WINDS
SHOULD BE A LITTLE LIGHTER COMPARED TO TUESDAY.

THE UPPER LOW WILL LINGER OVER THE WEST COAST AND PACIFIC NW
KEEPING ANY SIGNIFICANT WARMING IN CHECK. THE 850 MB TEMPS WILL
STAY IN THE SINGLE DIGITS AT LEAST THROUGH THE END OF THE WORK
WEEK SO NO MARINE LAYER IS EXPECTED TO REFORM ALONG THE COAST. BY
THE WEEKEND 850 MB TEMPERATURES MAY MODERATE TO AROUND 10 CELSIUS
THROUGH THE MEMORIAL DAY WEEKEND. FLOW ALOFT WILL REMAIN CYCLONIC
SO NO REAL WARM WEATHER EXPECTED BUT THE WEATHER LOOKS DRY AND
PLEASANT RIGHT THROUGH THE HOLIDAY WEEKEND.


&&

.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 SEA-BREEZE
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...
     .TNGT...SCA...PT ARENA TO PIGEON PT 10-60 NM
             SCA...PT REYES TO PIGEON PT 0-10 NM FROM MIDNIGHT
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM MIDNIGHT
             SCA...PT ARENA TO PT REYES 0-10 NM FROM 6 PM
             SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM FROM 6 PM

&&

$$

PUBLIC FORECAST: RWW
AVIATION/MARINE: DYKEMA

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