Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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989
FXUS66 KSEW 071137 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
318 AM PST SUN FEB 7 2016

.SYNOPSIS...A WEAK WARM FRONT WILL CLIP THE COAST AND NORTH CASCADES
TODAY. EXPECT DRY AND MILD WEATHER MONDAY AND TUESDAY AS A STRONG
RIDGE BUILDS OVER THE PACIFIC NORTHWEST. THE RIDGE WILL SHIFT EAST
BY WEDNESDAY OPENING THE DOOR TO MORE FRONTAL SYSTEMS BEGINNING
WEDNESDAY NIGHT.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS UPPER LEVEL RIDGE BUILDING
ALONG THE COAST WITH A WARM FRONT OFFSHORE EARLY THIS MORNING.
HIGH CLOUDS SPREAD OVER WESTERN WASHINGTON OVERNIGHT BUT THERE
STILL IS A FEW HOLES IN THE CLOUD COVER AT 3 AM. WITH SOME BREAKS
IN THE HIGH CLOUD COVER FOG FORMED ALONG THE I-5 CORRIDOR BETWEEN
ABOUT TACOMA AND CHEHALIS WITH VISIBILITIES 1 MILE OR LESS.
TEMPERATURES AT 3 AM WERE IN THE MID 30S TO MID 40S.

FORECAST PROBLEM FOR THE DAY IS HOW FAST THE UPPER LEVEL RIDGE
BUILDS ALONG THE COAST. SATELLITE IMAGERY SHOWS CLOUD TOP
TEMPERATURES WARMING OFF OF THE COAST WHICH GIVES THE EDGE TO THE
BUILDING RIDGE POSITION BUT THE STRONGEST PORTION OF THE WARM
FRONT WON`T REACH THE AREA UNTIL LATER THIS MORNING. 00Z MODEL
RUNS ARE ALL VERY CONSISTENT WITH 500 MB HEIGHTS NEAR AT LEAST IN
THE UPPER 570 DMS BY 00Z MONDAY. DOPPLER RADAR STARTING TO PICK
UP SOME ECHOES IN THE LAST HOUR OFF THE COAST. WILL UP THE POPS
INTO THE LIKELY CATEGORY FOR THE NORTH COAST WITH JUST CHANCE POPS
FOR THE REMAINDER OF THE COAST AND OVER THE NORTH CASCADES. EVEN
WITH THE RIDGE BUILDING OVER THE AREA PLENTY OF MID AND HIGH
LEVEL MOISTURE SO NOT MUCH SUNSHINE IF ANY AT ALL TODAY. HIGHS
WILL BE IN THE UPPER 40S TO MID 50S WITH THE WARMER LOCATIONS NEAR
THE LEWIS/COWLITZ COUNTY LINE.

RIDGE CONTINUING TO BUILD OVER THE AREA TONIGHT PUSHING THE WARM
FRONT WELL NORTH OF THE AREA. SURFACE GRADIENTS GOING OFFSHORE
OVERNIGHT INTO MONDAY MORNING. THIS WILL HELP RESTRICT FOG
DEVELOPMENT ACROSS WESTERN WASHINGTON WITH ONLY THE USUAL FOG
PRONE AREAS LIKE THE SOUTHWEST INTERIOR FOGGING IN BY MONDAY
MORNING. EVEN THE LOCATIONS THAT DO GET SOME FOG WILL SEE SUNSHINE
BY AFTERNOON. TEMPERATURES ALOFT WARMING CONSIDERABLY ON MONDAY
WITH THE 850 MB TEMPERATURES NEAR PLUS 14C BY 00Z TUESDAY. THIS
COMBINED WITH THE LOW LEVEL OFFSHORE FLOW PATTERN WILL RESULT IN
HIGH TEMPERATURES ANYWHERE FROM 5 TO 15 DEGREES ABOVE NORMAL...IN
THE MID 50S TO MID 60S WITH THE WARMER LOCATIONS ALONG THE COAST.
RECORD HIGHS ARE POSSIBLE ALONG THE NORTH COAST AND OVER THE
NORTHWEST INTERIOR.

UPPER LEVEL RIDGE SLOWLY DRIFTING EAST MONDAY NIGHT AND TUESDAY
BUT THE LOW LEVEL OFFSHORE FLOW PATTERN CONTINUES. PERSISTENCE
LOOKS LIKE A GOOD FORECAST FOR TUESDAY WITH ANOTHER ROUND OF HIGHS
IN THE MID 50S TO MID 60S.

.LONG TERM...EXTENDED MODELS CONTINUE TO SHOW A LACK OF
CONSISTENCY IN THE 00Z MODEL RUNS. THE GFS HAS A WEAK FRONT
REACHING THE COAST ON WEDNESDAY WHILE THE ECMWF AND CANADIAN KEEP
THIS FEATURE OFFSHORE. THE GFS HOLDS THE TRAILING COLD FRONT
OFFSHORE WEDNESDAY NIGHT WHILE THE ECMWF AND CANADIAN BRING THE
FRONT INTO WESTERN WASHINGTON. THE CANADIAN AND THE ECMWF BUILD A
WEAK RIDGE OVER WESTERN WASHINGTON ON THURSDAY WHILE THE GFS IS
FURTHER EAST WITH THIS FEATURE ALLOWING ANOTHER FRONT TO APPROACH
THE COAST. THERE IS A LITTLE BIT BETTER AGREEMENT ON FRIDAY WITH A
SYSTEM MOVING THROUGH FOLLOWED BY A TROUGH ON SATURDAY. CURRENT
FORECAST HAS THE HIGHEST POPS ON FRIDAY WITH CHANCE POPS FOR MOST
OF THE REST OF THE PERIOD. GIVEN THE MODEL INCONSISTENCIES WILL
STAY WITH THIS IDEA FOR THE MORNING FORECAST PACKAGE. FELTON

&&

.AVIATION...GENERALLY VFR TO MVFR FOR MOST TERMINALS IN WESTERN
WASHINGTON...THE EXCEPTION BEING THOSE PRONE TO FOG...SUCH AS
KOLM...WHERE VISIBILITIES ARE LIMITED AND CIGS ARE IFR OR LOWER.
THESE AREAS OF FOG LIKELY TO LINGER ON INTO MID TO LATE MORNING
HOURS BEFORE LIFTING. UPPER LEVEL WINDS REMAINING NORTHWESTERLY
THROUGH THE MORNING...TURNING WESTERLY IN THE AFTERNOON AS AN
UPPER LEVEL RIDGE CONTINUES TO MAKE ITS WAY EASTWARD.

INCOMING MOISTURE THIS AFTERNOON MAY BRING CIGS DOWN TO MVFR IN SOME
LOCATIONS. MODELS HINTING AT A THREAT FOR SOME PRECIP TO GO WITH
THOSE FALLING CIGS...BUT LOOKS INCREDIBLY SCATTERED AND QUICK MOVING
AT BEST. VCSH IS PRESENT IN MOST TAF SITES TO TAKE THIS INTO
ACCOUNT...BUT GIVEN THE QUICK MOVING/LIGHT AMOUNT NATURE OF ANY
PRECIP THAT DOES EMERGE...NOT SURE IF IT REALLY MERITS ANY
FURTHER MENTION THAN THAT. SMR

KSEA...VFR CONDITIONS WITH SOME MID AND HIGH LEVEL CLOUDS THIS
MORNING. CIGS WILL GRADUALLY COME DOWN BY THIS AFTERNOON IN RESPONSE
TO MOISTURE AND THE TAIL END OF A WARM FRONT BRUSHING BY.
CIGS OF 020-040 SHOULD BE EXPECTED FROM 18Z THIS MORNING TO ABOUT
03Z THIS EVNG...WITH CLEARING EXPECTED AFTERWARD.SMR

&&

.MARINE...HIGH PRES EAST OF THE CASCADES WILL PERSIST FOR MUCH OF
THE WEEK AHEAD. THIS WILL LEAD TO VARYING DEGREES OF OFFSHORE FLOW
THROUGH AT LEAST TUE NGT.

THE TAIL END OF A WARM FRONT WILL BRUSH THE COASTAL WATERS
TODAY...LEADING TO INCREASING E/SE WIND FOR THE COAST AND WEST
ENTRANCE. SMALL CRAFT ADVISORIES REMAIN IN PLACE THROUGH THIS
EVENING FOR THE INCREASED WINDS. WINDS ARE EXPECTED TO DIMINISH
TONIGHT. SMR

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED IN THE NEXT 7 DAYS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR COASTAL
     WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-
     COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO
     60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE
     OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
     SHOALWATER 10 TO 60 NM-COASTAL WATERS FROM POINT GRENVILLE
     TO CAPE SHOALWATER OUT 10 NM.

     SMALL CRAFT ADVISORY UNTIL 7 PM PST THIS EVENING FOR COASTAL
     WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-WEST
     ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

&&

$$

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