Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 031954
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1254 PM PDT TUE MAY 3 2016

.SYNOPSIS....HIGH CLOUDS WILL PUSH INTO THE AREA TODAY AS A SYSTEM
APPROACHES FROM THE PACIFIC. THIS WILL BRING COOLER TEMPERATURES
TO THE AREA BEGINNING WEDNESDAY ALONG WITH A POSSIBILITY OF
SHOWERS AND A RISK OF AFTERNOON THUNDERSTORMS...THESE CONDITIONS
ARE EXPECTED TO PERSIST INTO THE WEEKEND.

&&

.DISCUSSION...AS OF 1:00 PM PDT TUESDAY...MIX OF SUN AND CLOUDS
ACROSS OUR CWA TODAY WITH TEMPERATURES NEAR OR JUST A BIT COOLER
THAN YESTERDAY AT THIS TIME. HIGH CLOUDS MOVING THROUGH ARE IN
ADVANCE OF A PACIFIC SYSTEM ASSOCIATED WITH A LONGWAVE TROF THAT
WILL SLOWLY ADVANCE TO THE COAST. AT THE SAME TIME A CUT-OFF LOW
WILL FORM NEAR THE BASE OF THE TROF AND BE POSITIONED NEAR OUR
WATERS STARTING THURSDAY.

CUT-OFF LOWS OFTEN TO LEAD TO CHALLENGING FORECASTS AND THE
UPCOMING ONE IS NOT AN EXCEPTION TO THE RULE. LEADING EDGE OF
SHOWERS WILL MOVE TO WESTERN AND NORTHERN PARTS OF OUR AOR EARLY
TOMORROW AND THEN ACROSS OUR ENTIRE REGION LATE IN THE DAY. AS THE
LOW FORMS AND MOVES INLAND SOME TIME ON FRIDAY, CONVECTIVE
ACTIVITY SHOULD BE ON THE INCREASE. MORE UNSTABLE AIR WILL ALSO
COINCIDE WITH THE LOW LEADING TO A FEW THUNDERSTORMS ALONG WITH A
FEW CELLS LIKELY TO HAVE SMALL HAIL. THE LOW WILL MOVE TO THE FOUR
CORNERS REGION LATE ON SATURDAY WITH SHOWERS FORECAST TO END THAT
EVENING.

ALTHOUGH THERE WILL BE A CHANCE OF RAIN EACH DAY, AMOUNTS WILL BE
VERY LIGHT. IN FACT, RAINFALL TOTALS FROM THE CNRFC THROUGH THE
WEEKEND INDICATE LESS THAN 1/4" FOR MOST URBAN LOCATIONS. HIGHER
ELEVATIONS COULD LOCALLY SEE UP TO 1/2". ALL AREAS WILL SEE
COOLER TEMPERATURES WITH HIGHS IN THE UPPER 50S TO NEAR 70
EXPECTED TOMORROW THROUGH FRIDAY. THIS WOULD TRANSLATE TO A DROP
OF UP TO 20 DEGREES COMPARED TO THE HEAT LAST SUNDAY.

LONGER RANGE OUTLOOK FOR NEXT WEEK FAVORS A RIDGE RETURNING WITH
WARMER THAN NORMAL TEMPERATURES AND DRIER THAN NORMAL CONDITIONS.

&&

.AVIATION...AS OF 10:50 AM PDT TUESDAY...A COLD FRONTAL CLOUD
SHIELD IS OBSCURING THE STRATUS LAYER ON SATELLITE IMAGERY THIS
MORNING. SURFACE OBSERVATIONS HAVE REPORTED THE IFR/MVFR STRATUS
DECK HAS RETREATED EVERYWHERE EXCEPT FOR THE COAST (NEAR KHAF) AS
THE UPPER TROUGH APPROACHES. EARLIER THAN EXPECTED RETURN TO VFR
CIGS CAN BE ATTRIBUTED TO MIXING INDUCED BY APPROACHING SYSTEM.
BORDERLINE IFR/MVFR CIGS ARE EXPECTED TO RETURN THIS EVENING WITH
900-1200 FT CIGS FOR THE SAN FRANCISCO BAY AREA AND 400-800 FT CIGS
POSSIBLE FOR THE MONTEREY BAY AREA. WINDS GENERALLY LIGHT AND
ONSHORE TODAY NO GREATER THAN 15 KT.

VICINITY OF KSFO...VFR TODAY WITH A BKN-OVC DECK AOB 10000 FT.
ONSHORE WINDS UP TO 15 KT THROUGH THE AFTERNOON. BORDERLINE
MVFR/IFR CIGS RETURN AFTER 08Z WED. MED CONFIDENCE.

SFO BRIDGE APPROACH...SAME AS KSFO.

MONTEREY BAY TERMINALS...VFR THROUGH MIDDAY THEN COASTAL STRATUS
WILL ATTEMPT TO PUSH INLAND AS EARLY AS 00Z WED. MODELS INDICATING
RETURN TIME OF CIGS AT TERMINALS WILL RANGE FROM 01-08Z WED...
WITH MUCH EARLIER RETURN FOR KMRY AND KWVI AND A LATER RETURN FOR
INLAND SITES SUCH AS KSNS. ONSHORE WINDS UP TO 10KT .

&&

.MARINE...AS OF 12:31 PM PDT TUESDAY...LIGHT TO MODERATE NORTHERLY
WINDS PERSIST THROUGH MIDWEEK AS AN UPPER TROUGH DESCENDS INTO THE
REGION. WINDS AND SEAS STEADILY INCREASE AFTER MIDWEEK AS THE
UPPER LOW SHIFTS INLAND. THE UPPER LOW WILL ALSO BRING A SLIGHT
CHANCE OF THUNDERSTORMS TO THE COASTAL WATERS ON FRIDAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...SF BAY FROM 1 PM

&&

$$

PUBLIC FORECAST: BELL
AVIATION: DRP
MARINE: DRP


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