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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KMTR 040549
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
949 PM PST TUE MAR 3 2015

.SYNOPSIS...FORECAST REMAINS ON TRACK WITH A BUILDING RIDGE OF
HIGH PRESSURE ALONG THE WEST COAST WHICH WILL RESULT IN DRY
WEATHER CONDITIONS AND A SLIGHT WARMING TREND THROUGH THE WEEKEND.

&&

.DISCUSSION...AS OF 8:51 PM PST TUESDAY...MOSTLY CLEAR SKIES ARE
BEING REPORTED ACROSS THE FORECAST AREA THIS EVENING AS HIGH
PRESSURE BEGINS TO BUILD OVER COASTAL CALIFORNIA. DEW POINT
DEPRESSIONS ARE RUNNING BETWEEN 3 TO 4 DEGREES CELSIUS AT MOST
LOCATIONS WHICH WHEN COMBINED WITH THE CLEAR SKIES SUGGESTS A
POSSIBILITY OF LATE NIGHT EARLY MORNING FOG. HOWEVER...FORECAST
MODELS ARE SUGGESTING LIGHT OFFSHORE WINDS TONIGHT WHICH SHOULD
MIX THE ATMOSPHERE ENOUGH TO PREVENT WIDESPREAD FOG FROM FORMING.

THE 0000Z GFS40 AND 1200Z ECMWF HAVE INITIALIZED WELL WITH THE
CURRENT SYNOPTIC PATTERN AND REMAIN IN GOOD AGREEMENT THROUGH THE
WEEKEND. BOTH MODELS BUILD AN UPPER LEVEL RIDGE OVER THE WEST
COAST WHICH IS EXPECTED TO REMAIN IN PLACE THROUGH AT LEAST
SUNDAY. GENERALLY SPEAKING THE MODELS ARE FORECASTING LIGHT
OFFSHORE WINDS AT THE SURFACE THROUGH MUCH OF THE WEEKEND. THE
EXCEPTION TO THIS STATEMENT WILL BE THE AFTERNOON SEA
BREEZE...WHICH WILL BE GUSTY AT TIMES. THE OFFSHORE FLOW WILL
FURTHER PROMOTE WARM DAY TIME TEMPERATURES. ON THE FLIP SIDE THE
OFFSHORE WINDS WILL LIMIT THE OCEAN`S INFLUENCE ON SURFACE
TEMPERATURES SO EXPECT CLEAR CHILLY NIGHTS TO PREVAIL THROUGH AT
LEAST SATURDAY. THE CURRENT FORECAST PACKAGE HANDLES THIS SCENARIO
WELL. THEREFORE...NO UP DATES ARE NEEDED AT THIS TIME.

.DISCUSSION...AS OF 02:24 PM PST TUESDAY...A MID/UPPER LEVEL RIDGE
OFF OF THE WEST COAST WILL SLOWLY STRENGTHEN AND BUILD INLAND
THROUGH LATE WEEK AS THE LONG-WAVE TROUGH AXIS OVER SOUTHERN
CALIFORNIA SHIFTS EASTWARD. AS A RESULT...850 MB TEMPERATURES ARE
FORECAST TO WARM ABOVE 10 DEGREES C AND BRING SURFACE TEMPERATURES
INTO THE 70S FOR MOST LOCATIONS BY THURSDAY. THESE WARM AND DRY
CONDITIONS ARE THEN FORECAST TO PERSIST THROUGH THE UPCOMING
WEEKEND AND LIKELY INTO EARLY NEXT WEEK AS THE RIDGE REMAINS
PARKED OVER MUCH OF THE REGION. WITH WEAK OFFSHORE FLOW POSSIBLE
OVER INLAND AREAS THIS WEEKEND...A FEW SPOTS MAY EVEN REACH OR
EXCEED THE 80 DEGREE MARK. WITH LIMITED MOISTURE IN THE BOUNDARY
LAYER...DO NOT EXPECT MUCH IN THE WAY OF STRATUS DURING THE LATE
NIGHT/EARLY MORNING HOURS THROUGH EARLY NEXT WEEK.

THE MEDIUM/LONG RANGE MODELS CONTINUE TO SHOW THE MID/UPPER LEVEL
RIDGE SHIFTING EASTWARD AND WEAKENING BY THE MIDDLE OF NEXT WEEK.
THIS PATTERN CHANGE WOULD ALLOW FOR AN UPPER LEVEL TROUGH TO IMPACT
THE PACIFIC NORTHWEST AND BRING WIDESPREAD RAINFALL TO THE SAN
FRANCISCO/MONTEREY BAY REGION WEDNESDAY INTO THURSDAY OF NEXT WEEK.
TEMPERATURES WILL ALSO COOL OVER THE REGION DURING THE LATTER HALF
OF NEXT WEEK AS A RESULT. WILL CONTINUE TO MONITOR THIS POSSIBLE
PATTERN CHANGE FOR NEXT WEEK...STAY TUNED.

&&

.AVIATION...AS OF 9:48 PM PST TUESDAY...LIGHT OFFSHORE WINDS ARE
LIKELY VERY LATE TONIGHT AND WEDNESDAY MORNING AS THE CA COASTAL
TROUGH MIGRATES TO THE COAST AND SLIGHTLY OFFSHORE. AS A RESULT
IT`S A HIGH CONFIDENCE VFR FORECAST FOR THE BAY AREA TERMINALS.

LOW CLOUD COVER IS POSSIBLE IN THE MONTEREY BAY AREA THROUGH EARLY
WEDNESDAY MORNING. SCATTERED TO BROKEN MVFR CLOUD COVER IS THE BEST
GUESS FOR TONIGHT. MVFR CIGS ARE SUPPORTED BY NON-EVIDENCE OF A
CAPPING LOW LEVEL INVERSION. IFR NOT IN THE 06Z KMRY AND KSNS TAFS
BUT COULD HAVE BRIEF WINDOW 1-2 HOURS IFR CIGS EARLY WEDNESDAY MORNING
FROM EITHER THE CLOUDS BEGINNING TO MIX A BIT ASSOCIATED WITH A
FORECASTED EDDY CIRCULATION OVER THE MONTEREY BAY PER THE WRF MODEL
OR AT THE START OF THE DAILY VERTICAL MIXING PRIOR TO CLEARING.

WEAK TO LOCALLY MODERATE ONSHORE WINDS RETURN ALL AREAS BY WEDNESDAY
AFTERNOON AS THE NAM SHOWS THE TROUGH MOVING BACK INLAND...BUT WE
COULD SEE A SIMILAR PATTERN WITH A BRIEF PERIOD OF WEAK OFFSHORE
WIND DEVELOPING ONCE AGAIN VERY LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING.

VICINITY OF KSFO...VFR. WESTERLY WINDS RETURN BY MID TO LATE WEDNESDAY
AFTERNOON. HIGH CONFIDENCE.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...24 HOUR TRENDS SHOW SLIGHTLY HIGHER
DEW-POINT TEMPERATURES. LOW CLOUD DEVELOPMENT HAS NOT GAINED MUCH
TRACTION THIS EVENING BUT NW WIND FLOW OVER THE MONTEREY BAY AND
NIGHT-TIME COOLING STILL COULD CONTRIBUTE TO LOW CLOUD DEVELOPMENT
ALONG THE MONTEREY BAY SHORELINE. THE DURATION OF THE LOW CLOUD COVER
TONIGHT IS HIGHLY DEPENDENT UPON THE CHARACTERISTICS OF THE EDDY
CIRCULATION PREDICTED TO DEVELOP OVER THE BAY BY THE WRF MODEL.
GOOD MIXING PROCESSES WEDNESDAY RAISES CHANCES FOR VFR TO RETURN DURING
THE DAY BUT LOW CLOUDS MAY NOT BE THAT FAR AWAY FROM THE TERMINALS
TOMORROW EVENING. LOW TO MODERATE CONFIDENCE FORECAST.

&&

.MARINE...AS OF 8:10 PM PST TUESDAY...HIGH PRESSURE OVER THE
EASTERN PACIFIC WILL MAINTAIN NORTHERLY WINDS OVER THE COASTAL
WATERS THROUGH MID TO LATE WEEK. LOCALLY GUSTY WINDS WILL BE
POSSIBLE NORTH OF POINT REYES...ESPECIALLY THE OUTER WATERS. SEAS
ARE EXPECTED TO BE MODERATE AND GRADUALLY DECREASE THROUGH THE
WEEK.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PT ARENA TO PT REYES 10-60 NM UNTIL 3 AM

&&

$$

PUBLIC FORECAST: LARRY
AVIATION/MARINE: CANEPA

VISIT US AT WEATHER.GOV/SANFRANCISCO

FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSBAYAREA
WWW.TWITTER.COM/NWSBAYAREA
WWW.YOUTUBE.COM/NWSBAYAREA




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.