Gale Warning 25, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
420 PM PDT MON MAR 30 2009

.SYNOPSIS...RAIN WILL INCREASE ACROSS WESTERN WASHINGTON OVERNIGHT
AS A COLD FRONT APPROACHES FROM THE NORTHWEST. THE COLD FRONT WILL
PASS THROUGH THE AREA ON TUE WITH STRONG WESTERLY FLOW ENHANCING
PRECIPITATION OVER THE MOUNTAINS. HEAVY SNOW WILL CONTINUE ACROSS
THE CASCADES THROUGH TUESDAY NIGHT. ANOTHER FRONTAL SYSTEM WILL
AFFECT THE REGION WEDNESDAY INTO EARLY THURSDAY FOR MORE WET WEATHER
AND COOL TEMPERATURES. DRIER WEATHER IS EXPECTED BY FRIDAY AS AN
UPPER LEVEL RIDGE BUILDS OVER THE REGION.

&&

.SHORT TERM...RAIN WILL INCREASE ACROSS WESTERN WASHINGTON TONIGHT
AS A COLD FRONT APPROACHES FROM THE NW. IN FACT KATX RADAR ALREADY
PICKING UP ON LIGHT ECHOES ACROSS THE NORTH INTERIOR...WITH LIGHT
RAIN REPORTED ALONG THE NORTH COAST AS WELL. ZOOMING OUT...A LOOK
AT THE IR SATELLITE SHOWS A FAIRLY DECENT MOISTURE SWATH WITH THIS
SYSTEM...WITH A PLUME STRETCHING BACK PAST 140W. MODELS REALLY RAMP
UP THE PRECIP TUE MORNING AS THE COLD FRONT PASSES THROUGH THE
REGION. PRECIPITATION WILL BE ENHANCED ACROSS THE MOUNTAINS WITH
STRONG OROGRAPHIC FLOW...WINDS AT 850 MB ON THE ORDER OF 40 KT AS A
NWLY JET NOSES IN. SNOW LEVELS WILL REMAIN NEAR 2000-2500 FT WITH
ANOTHER ROUND OF HEAVY SNOW EXPECTED...ESPECIALLY FOR THE WEST
SLOPES OF THE CASCADES. SHOWERS WILL BE MAINLY CONFINED TO THE
CASCADES DURING THE EVENING HOURS...BUT WILL NEED TO WATCH FOR A
DEVELOPING PUGET SOUND CONVERGENCE ZONE WHICH WILL CREATE LOCALLY
HEAVY SHOWERS BETWEEN STEVENS AND SNOQUALMIE. WILL CONVERT THE
WINTER STORM WATCH OVER TO A WINTER STORM WARNING FOR THE N AND
CENTRAL CASCADES...WITH LESSER SNOW AMOUNTS EXPECTED FOR THE
OLYMPICS.

AFTER A VERY BRIEF BREAK IN THE WEATHER LATE TUE NIGHT...WILL SEE
RAIN INCREASING ONCE AGAIN ACROSS THE PAC NW ON WED AS ANOTHER WARM
FRONT APPROACHES THE REGION. POPS WILL REMAIN NEAR CATEGORICAL AS
THIS SYSTEM ALSO LOOKS PRETTY JUICY ON SATELLITE. THE COLD FRONT AND
TRAILING UPPER LEVEL TROUGH WILL KEEP THE AREA COOL...MOIST AND
UNSTABLE THROUGH THU. 33

.LONG TERM...AFTER AN ACTIVE FIRST HALF OF THE WEEK...THE LATER HALF
IS LOOKING MUCH DRIER AS AN UPPER LEVEL RIDGE BUILDS OVER THE
REGION. COULD ACTUALLY SEE TEMPERATURES REACHING BACK TO OUR
SEASONAL NORMS WITH HIGHS IN THE LOW TO MID 50S.

WILL SIDE WITH THE WEAKER AND SLOWER ECMWF SOLUTION OVER THE WEEKEND
AS THE MODELS DEVELOP A DEEP AND ELONGATED UPPER LEVEL TROUGH
OFFSHORE. AS A RESULT...DECREASED POPS ACROSS THE BOARD WITH SOME
PARTLY SUNNY TO MOSTLY SUNNY SKIES POSSIBLE. 33

&&

.AVIATION...NORTHWESTERLY FLOW ALOFT WILL PERSIST THROUGH AT LEAST
MID WEEK. THE FIRST IN A SERIES OF PACIFIC FRONTAL SYSTEMS HAS BEGUN
TO AFFECT WESTERN WASHINGTON AS A WARM FRONT BRUSHES THE REGION FROM
THE NORTHWEST TONIGHT. ABUNDANT MOISTURE AND LIGHT RAIN ALONG WITH
THE WARM FRONT WILL CONTINUE TO SPREAD INLAND AND SOUTH TONIGHT.
CEILINGS OVER MOST LOCATIONS IN WESTERN WASHINGTON HAVE BEEN
HOVERING JUST ABOVE MVFR LEVELS THROUGH THE AFTERNOON...EXPECT
CEILINGS TO LOWER TO MVFR AND LOCAL IFR BY LATE EVENING WITH THE
INCREASING LOW LEVEL MOISTURE AND PRECIPITATION. LOW LEVEL FLOW WILL
STRENGTHEN WITH THE TRAILING COLD FRONT TUESDAY...REMAINING
SOUTHERLY FOR THE CENTRAL AND SOUTH SOUND...NORTHWESTERLY FOR THE
NORTH SOUND AND INTERIOR...AND STRONGLY ONSHORE FOR THE COAST AND
STRAIT. OVERALL CONDITIONS  SHOULD IMPROVE MOST AREAS TUESDAY
AFTERNOON TO VFR...WITH LINGERING MVFR CONDITIONS NEAR REMAINING
SHOWERS.

KSEA...SOUTHWEST WIND 8-12 KT. CIGS LOWERING TO NEAR 2000 FEET WITH
LIGHT RAIN BY 06Z.

&&

.MARINE...THE FIRST IN A SERIES OF PACIFIC FRONTAL SYSTEMS HAS BEGUN
TO AFFECT THE COASTAL WATERS AS A WARM FRONT BRUSHES THE REGION FROM
THE NORTHWEST. ABUNDANT MOISTURE AND LIGHT RAIN ALONG WITH THIS WARM
FRONT WILL CONTINUE TO SPREAD INTO THE INTERIOR WATERS OVERNIGHT.
SMALL CRAFT CRITERIA SOUTHWESTERLY WINDS WILL PREVAIL ALONG COAST
AND WEST ENTRANCE AHEAD OF THE TRAILING COLD FRONT. ONSHORE FLOW
WILL STRENGTHEN WITH THE COLD FRONT TUESDAY...BRINGING VERY STRONG
WINDS TO ALL WATERS...ESPECIALLY THE CENTRAL AND EAST
STRAIT...NORTHERN INTERIOR AND ADMIRALTY INLET WATERS. STRONG 850 MB
WINDS COUPLED WITH THE STRONG ONSHORE GRADIENTS LEND SUPPORT THE
IDEA THAT WINDS WILL BE CLOSE TO GALE...ACCORDINGLY A GALE WATCH HAS
BEEN ISSUED FOR THE CENTRAL AND EAST STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET FOR TUESDAY. A SMALL CRAFT ADVISORY HAS
BEEN ISSUED ALL OTHER WATERS THROUGH TUESDAY EVENING. WINDS SHOULD
DIMINISH BY LATE TUESDAY NIGHT AND INTO WEDNESDAY MORNING.

A SECOND AND SIMILAR FRONTAL SYSTEM WILL AFFECT THE REGION WEDNESDAY
AND THURSDAY. MODELS STICKING WITH TIMING THE WARM FRONT FOR THE
COAST WEDNESDAY MORNING...FOLLOWED BY THE COLD FRONT LATE WEDNESDAY
NIGHT. THIS SYSTEM WILL BRING ANOTHER BOUT OF SMALL CRAFT ADVISORY
WINDS OVER THE FORECAST AREA...AND POSSIBLY GALE FORCE WINDS. IN
ADDITION SIGNIFICANT WESTERLY SWELL 14 TO 16 FT ARE EXPECTED TO MOVE
INTO THE AREA LATER THURSDAY THROUGH FRIDAY.

&&

.AVALANCHE...THE NEXT STRONG FRONTAL SYSTEM SHOULD ALSO CROSS THE
OLYMPICS AND CASCADES TUESDAY MORNING. STRONG NORTHWEST FLOW
ALOFT...OROGRAPHIC AND CONVERGENCE EFFECTS SHOULD CONTINUE TO
ENHANCE SNOWFALL FOLLOWING THE FRONT IN THE OLYMPICS AND CASCADES ON
TUESDAY. THIS SHOULD LEAD TO A SIGNIFICANTLY INCREASING AVALANCHE
DANGER TUESDAY. AN AVALANCHE WATCH IS CURRENTLY IN EFFECT FOR
TUESDAY. PLEASE VISIT WWW.NWAC.US FOR DETAILS. FERBER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING CASCADES.
     WINTER WEATHER ADVISORY OLYMPICS.
     AVALANCHE WATCH CASCADES AND OLYMPICS.

PZ...GALE WATCH FOR THE CENTRAL AND EAST STRAIT...NORTHERN INLAND
     WATERS...AND ADMIRALTY INLET TUESDAY MORNING THROUGH
     TUESDAY NIGHT.
     SMALL CRAFT ADVISORY FOR THE CENTRAL AND EAST STRAIT TONIGHT.
     SMALL CRAFT ADVISORY FOR THE COASTAL WATERS AND WEST ENTRANCE
       STRAIT OF JUAN DE FUCA NOON TODAY THROUGH TUESDAY NIGHT.
     SMALL CRAFT ADVISORY PUGET SOUND AND HOOD CANAL TUESDAY THROUGH
       TUESDAY NIGHT.

WWW.WEATHER.GOV/SEATTLE