000
FXUS66 KMTR 221137
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
437 AM PDT WED MAY 22 2013

.DISCUSSION...AS OF 3:16 AM PDT WEDNESDAY...COOL DRY AIR CONTINUES TO
FILTER INTO THE REGION OVERNIGHT...AS AN UPPER LEVEL LOW PRESSURE
SYSTEM REMAINS STALLED OVER THE PACIFIC NORTHWEST COAST.
TEMPERATURES COOLED INTO THE MID 40S TO LOW 50S SO FAR...AND ARE
FORECAST TO FALL ANOTHER 5 DEGREES IN THE NEXT FEW HOURS...WITH
READINGS MAINLY IN THE 40S. OTHERWISE...MODERATE NORTHWEST WINDS
CONTINUED ACROSS THE REGION WELL INTO THE OVERNIGHT HOURS...AS
SURFACE HIGH PRESSURE DOMINATED THE EASTERN PACIFIC...WITH A
SURFACE LOW OVER SOUTHERN NEVADA. WIND GUSTS OVER 20 MPH WERE
COMMON THROUGH THE AREA AND ARE FORECAST TO SLOWLY SUBSIDE INTO
THE EARLY MORNING HOURS.

THE UPPER LOW OVER THE PACIFIC NORTHWEST WILL DOMINATE THE WEATHER
PATTERN THROUGH THE END OF THE WORK WEEK...WITH DAYTIME HIGH
TEMPERATURES REACHING THE 60S ALONG THE COAST...AND NEAR 70
INLAND. THESE TEMPERATURES ARE AROUND 5 DEGREES BELOW NORMAL FOR
THE MIDDLE OF MAY. GUSTY NORTH TO NORTHWEST WINDS WILL ALSO BE
PRESENT ACROSS THE REGION EACH AFTERNOON INTO THE EVENING HOURS.
ONE OF THE MORE DIFFICULT PARTS OF THE FORECAST INTO THE WEEKEND
WILL BE THE POSSIBILITY OF LOW CLOUDS ALONG THE COAST. THE SHORT
TERM MODELS INDICATE THAT BOUNDARY LAYER RH VALUES INCREASE ALONG
THE COAST OVER THE NEXT 24 HOURS...HOWEVER...NUMERICAL GUIDANCE
INDICATES THE COAST WILL REMAIN CLEAR. WITH THE LACK OF A MARINE
LAYER...DECIDED TO KEEP OUT ANY MENTION OF LOW CLOUDS ALONG THE
COAST. IF LOW CLOUDS DO FORM...THEY WILL LIKELY BE VERY PATCHY IN
NATURE.

NO MAJOR CHANGES IN THE WEATHER PATTERN UNTIL THE FIRST PART OF
NEXT WEEK. THE UPPER LOW OFF THE PACIFIC NORTHWEST COAST IS FORCED
EAST INTO THE GREAT BASIN MONDAY INTO TUESDAY AS A MORE POWERFUL
STORM IN THE GULF OF ALASKA MOVES SLOWLY SOUTHEAST TOWARD THE
REGION. BOTH THE GFS AND ECMWF ARE IN GOOD AGREEMENT ABOUT CHANCES
OF PRECIPITATION AND TIMING OF RAIN ADDING CONFIDENCE TO THE
FORECAST. THE MEDIUM RANGE MODELS INDICATE THE RAIN WILL QUICKLY
SPREAD FROM NORTH TO SOUTH ALONG THE COAST MONDAY INTO TUESDAY.
THE GREATEST CHANCE FOR RAIN WILL REMAIN OVER THE NORTH BAY. WE
WILL CONTINUE TO MONITOR THE CHANCES FOR RAIN CLOSELY INTO THE
WEEKEND AND PROVIDE MORE SPECIFIC INFORMATION REGARDING TIMING AND
AMOUNT OF RAIN AS THE EVENT NEARS.

OTHERWISE...THE CLIMATE PREDICTION CENTERS 8 TO 14 DAY OUTLOOK
(VALID FROM MAY 29TH THROUGH JUNE 4TH) CALL FOR BELOW NORMAL
TEMPERATURES!

&&

.AVIATION...AS OF 4:37 AM PDT WEDNESDAY...MAINLY CLEAR SKIES WILL
PERSIST THROUGH THE FORECAST PERIOD AS A TIGHT GRADIENTS MAINTAIN
STRONG WINDS ACROSS THE REGION. GUSTY WINDS WILL EASE A BIT THIS
MORNING THEN STRENGTHEN ONCE AGAIN BY THE AFTERNOON.

VICINITY OF KSFO...VFR. STRONG AND GUSTY WEST WINDS SUSTAINED AT
AROUND 15 TO 25 KT WITH GUSTS AS HIGH AS 30 KT EXPECTED THROUGH
THE MORNING HOURS. WINDS WILL STRENGTHEN TO AROUND 30 KT WITH
GUSTS TO 40 KT AFTER 20Z. AN AIRPORT WEATHER WARNING FOR WINDS
WILL BE EFFECT FROM 20Z (1 PM PDT) THIS AFTERNOON TO 04Z (9 PM
PDT) THIS EVENING.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR. MODERATE AND LOCALLY GUSTY
WEST WINDS WILL CONTINUE THROUGH THE FORECAST PERIOD. STRONGEST
WINDS EXPECTED THIS AFTERNOON.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PIGEON PT TO PT PINOS 0-10 NM
             GLW...PT ARENA TO PIGEON PT 10-60 NM
             GLW...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             GLW...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM
             SCA...PT ARENA TO PT REYES 0-10 NM
             SCA...PT REYES TO PIGEON PT 0-10 NM
             SCA...ROUGH BAR ADVISORY FOR SF BAR

&&

$$

PUBLIC FORECAST: RILEY
AVIATION/MARINE: CW

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