Small Craft Advisory 914, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 PM PST SUN FEB 5 2012

.SYNOPSIS...AN UPPER RIDGE WILL KEEP THE WEATHER DRY THROUGH
TUESDAY. OFFSHORE FLOW WILL PRODUCE LOCALLY GUSTY WINDS NEAR THE
MOUNTAINS THROUGH TUESDAY...WHILE WIND PROTECTED AREAS WILL
EXPERIENCE STAGNANT CONDITIONS AND PATCHY MORNING FOG. RAIN IS
POSSIBLE STARTING TUESDAY NIGHT OR WEDNESDAY AS THE FIRST IN A
SERIES OF WEAK FRONTS MOVES INLAND.

&&

.SHORT TERM...AN UPPER LEVEL RIDGE WILL REMAIN OVER THE PACIFIC
NORTHWEST THROUGH WEDNESDAY...WEAKENING A BIT TUESDAY AND WEDNESDAY.
A FRONT WILL APPROACH FROM THE WEST MONDAY AND TUESDAY...BRINGING
SOME CLOUDS BUT NO RAIN AS IT WEAKENS OFFSHORE. THE MAIN IMPACT WILL
BE TO STRENGTHEN THE LOW LEVEL OFFSHORE FLOW. WINDS NEAR THE
CASCADES FOOTHILLS WILL INCREASE MONDAY...PEAKING MONDAY NIGHT
BEFORE EASING ON TUESDAY. A WIND ADVISORY WILL BE ISSUED FOR THIS.
THE OFFSHORE FLOW SHOULD HELP WARM HIGHS ABOVE NORMAL AGAIN MONDAY.
GUIDANCE HAS HIGHS NEAR NORMAL. THE FORECAST IS FOR HIGHS TO BE
SEVERAL DEGREES ABOVE NORMAL MOST AREAS. HIGHS ARE EXPECTED TO LOWER
A FEW DEGREES TUESDAY AS THE OFFSHORE FLOW AND UPPER RIDGE WEAKEN
BUT STILL BE A LITTLE ABOVE NORMAL. THE SOUTH INTERIOR WILL CONTINUE
TO SEE PATCHY NIGHT AND MORNING FOG WITH LIGHTER WINDS AND STAGNANT
CONDITIONS THROUGH AT LEAST MONDAY....POSSIBLY INTO TUESDAY. A VERY
WEAK FRONT WILL BRING A CHANCE OF RAIN WEDNESDAY. THE GFS IS
BASICALLY DRY BUT THE ECMWF HAS A GOOD BIT OF RAIN. THE FORECAST IS
A MIDDLE GROUND COMPROMISE BETWEEN THE TWO...PERHAPS WEIGHTED A BIT
MORE TOWARDS THE DRIER GFS GIVEN RECENT MODEL TRENDS. SCHNEIDER

.LONG TERM...BOTH THE GFS AND ECMWF SHOW THE UPPER RIDGE REBUILDING
OVER THE AREA ON THURSDAY. CONFIDENCE WAS HIGH ENOUGH THAT ALL
MENTION OF PRECIPITATION FOR THURSDAY WAS REMOVED FROM THE FORECAST
EXCEPT AT THE COAST. CONFIDENCE IN THE DETAILS AFTER THAT IS NOT AS
HIGH. THE GFS IS FAIRLY DRY UNTIL ABOUT SUNDAY. THE ECMWF IS QUITE A
BIT WETTER. NEITHER MODEL IS SHOWING MUCH RUN TO RUN CONTINUITY. FOR
NOW THE FORECAST IS FOR A BROAD-BRUSH CHANCE OF RAIN FRIDAY AND
SATURDAY THEN RAIN LIKELY ON SUNDAY. SCHNEIDER

&&

.HYDROLOGY...NO FLOODING IS EXPECTED IN THE FORECAST AREA DURING THE
NEXT 7 DAYS. SCHNEIDER

&&

.AVIATION...A STRONG UPPER LEVEL RIDGE WILL REMAIN OVER THE PACIFIC
NORTHWEST THROUGH MONDAY...KEEPING THE AIR MASS GENERALLY DRY AND
STABLE. A SURFACE RIDGE OVER THE NORTHERN ROCKIES WILL MAINTAIN DRY
LOW LEVEL EASTERLY OFFSHORE FLOW ACROSS W WA. THE ONLY CLOUD COVER
EXPECTED OVER THE AREA INTO EARLY MONDAY MORNING IS SCT-BKN CIRRUS.
THERE WILL BE PATCHY MORNING FOG OVER THE S PUGET SOUND AND SW
INTERIOR 10Z-16Z MONDAY. EASTERLY LOW LEVEL FLOW WILL INCREASE ON
MONDAY AND MAY BE STRONG ENOUGH TO PRODUCE LOW LEVEL TURBULENCE OVER
AND IMMEDIATELY W OF THE CASCADES.

KSEA...JUST SCT-BKN CIRRUS TONIGHT. SURFACE WINDS WILL REMAIN
NORTHERLY 4-8 KT THE REMAINDER OF THIS AFTERNOON...THEN BECOME MORE
NE THIS EVENING. KAM

&&

.MARINE...A SURFACE RIDGE OVER THE NORTHERN ROCKIES COMBINED WITH
LOWER PRESSURE OFFSHORE WILL MAINTAIN EASTERLY OFFSHORE FLOW OVER W
WA THROUGH MOST OF THIS WEEK.

ANOTHER FRONTAL SYSTEM WILL SLOWLY APPROACH THE AREA LATE TONIGHT
THROUGH TUESDAY CAUSING A GRADUAL INCREASE IN OFFSHORE FLOW.
PRESSURE GRADIENTS SHOULD BE STRONG ENOUGH THROUGH THE STRAIT TO
PRODUCE GALE FORCE EASTERLIES AT THE WEST ENTRANCE LATE TONIGHT.
WILL KEEP A SCA GOING FOR THE W ENTRANCE AND THE ADJOINING COASTAL
ZONE PZZ150 UNTIL 12Z THEN REPLACE THAT WITH A GALE WARNING THAT
WILL RUN THROUGH MONDAY NIGHT. MESOSCALE MODELS ON SHOW MARGINAL SCA
E-SE WINDS OVER PARTS OF THE REMAINING COASTAL WATERS ON MONDAY...SO
WILL GO AHEAD AND ISSUE A SCA TO COVER THIS.

PRESSURE GRADIENTS SHOULD START WEAKENING TUESDAY AS THE RAPIDLY
WEAKENING FRONT NEARS THE COASTAL WATERS. HOWEVER THE FRONT MAY
STILL END UP REACHING THE COAST IN A VERY WEAKENED STATE LATE
TUESDAY. GFS SHOWS ANOTHER WEAK FRONT MOVING EAST ACROSS THE AREA ON
WEDNESDAY. BOTH THE GFS/ECMWF MOVE A STRONGER SYSTEM NORTHWARD
OFFSHORE ALONG 135W LATE IN THE WEEK. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...AIR STAGNATION ADVISORY TACOMA AND VICINITY...HOOD CANAL
     AREA...SOUTHWEST INTERIOR...AND LOWER CHEHALIS VALLEY THROUGH
     MONDAY AFTERNOON.
    .WIND ADVISORY EAST PUGET SOUND LOWLANDS MONDAY MORNING THROUGH
      TUESDAY MORNING.

PZ...SMALL CRAFT ADVISORY TONIGHT WEST ENTRANCE JUAN DE FUCA AND
     PZZ150.
    .GALE WARNING MONDAY AND MONDAY NIGHT WEST ENTRANCE JUAN DE
     FUCA AND PZZ150.
    .SMALL CRAFT ADVISORY OUTER COASTAL WATERS MONDAY.

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.