Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 201716
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU NOV 20 2014

.SYNOPSIS...WEAK LOW PRESSURE ALOFT WILL PREVAIL OVER THE REGION
TODAY FOR SCATTERED SHOWERS. THE AREA WILL BE BETWEEN SYSTEMS
TONIGHT. A STRONGER PACIFIC STORM WILL IMPACT THE REGION ON FRIDAY
FOR LOCALLY HEAVY RAIN AND GUSTY WINDS...ALONG WITH THE POTENTIAL
FOR DECENT SNOWFALL IN THE MOUNTAINS. THE WEATHER PATTERN WILL
REMAIN WET AND UNSETTLED THIS WEEKEND.

&&

.SHORT TERM...AS A COUPLE OF WEAK LOW PRESSURE SYSTEMS MOVE INLAND
TO OUR NORTH AND SOUTH...RECENT MODEL SOLUTIONS SHOW SHOWERS
LINGERING MORE TODAY AND TONIGHT THAN PREVIOUSLY THOUGHT. RIGHT NOW
THE FORECAST FOR THE LOWLANDS SHOWS TONIGHT MAINLY DRY...BUT MAY
BUMP UP THE POPS AFTER REEVALUATING LATER TODAY.

A STRONGER PACIFIC STORM WILL IMPACT THE REGION ON FRI FOR LOCALLY
HEAVY RAIN AND GUSTY WINDS IN THE FAVORED AREAS...COAST AND NORTH
INTERIOR. A WIND ADVISORY WILL LIKELY BE NEEDED FOR THESE AREAS FOR
LATE FRI MORNING THROUGH AT LEAST FRI AFTERNOON.

IT LOOKS LIKE THE CENTRAL AND NORTH CASCADES ABOVE 4000 FEET WILL
RECEIVE WINTER WEATHER ADVISORY CRITERIA SNOWFALL AMOUNTS OR AMOUNTS
IN THE 6 TO 11 INCH RANGE FRI NIGHT...ALTHOUGH IT IS POSSIBLE THAT
THE MOUNT BAKER SKI AREA COULD RECEIVE ABOUT A FOOT OF SNOW.

THE COLD FRONT WILL SWEEP ACROSS THE CWA FRI NIGHT. EXPECT THE
UPPER TROF TO MOVE ACROSS THE REGION EARLY SATURDAY. THE AIR MASS
WILL REMAIN UNSTABLE ENOUGH FOR PLENTY OF SHOWERS ON SATURDAY. IN
ADDITION...A PUGET SOUND CONVERGENCE ZONE COULD DEVELOP IN ITS
FAVORED LOCATION...NEAR THE KING/SNOHOMISH COUNTY BORDER...IN THE
WAKE OF THE COLD FRONT. JSMITH

.LONG TERM...ANOTHER LOW PRESSURE SYSTEM WILL MOVE ACROSS THE
PACIFIC NORTHWEST ON SUNDAY...THUS POPS WERE BUMPED UP TO
CATEGORICAL. MONDAY AND BEYOND...BOTH THE GFS AND ECMWF SHOW
MOISTURE BEING TRANSPORTED TO THE PACIFIC NW VIA THE JET
STREAM...HOWEVER THE GFS HAS THE MOISTURE HITTING BC AND US STAYING
DRY WITH A RIDGE PATTERN...WHEREAS THE ECMWF HAS A WETTER SOLUTION
FOR US WITH THE MOISTURE HITTING US DIRECTLY. THEREFORE MUCH
UNCERTAINTY EXISTS IN THE FORECAST FOR EARLY NEXT WEEK. JSMITH

&&

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

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH WILL REMAIN OVER W WA TODAY IN
THE WAKE OF LAST NIGHTS COLD FRONT. RESIDUAL LOW LEVEL MOISTURE WILL
KEEP CIGS BKN030-060 THROUGH TODAY...WITH SPOTTY MVFR CIGS
BKN015-030 MAINLY AROUND WEAK SHOWERS THROUGH ABOUT 00Z/5 PM. THE
AIR MASS IS MAINLY STABLE.

INCREASING W FLOW ALOFT WILL DRIVE AN APPROACHING FRONTAL
SYSTEM...ALONG 140W AT 1630Z/830 AM...ACROSS W WA FRIDAY AND FRIDAY
NIGHT. GUSTY WINDS ARE EXPECTED ALONG THE COAST AND PARTS OF THE N
INTERIOR ALONG WITH A RETURN OF MVFR CONDITIONS THROUGHOUT THE AREA.

KSEA...MAINLY VFR TODAY WITH CIGS BKN040-060. COULD SEE SOME BRIEF
CIGS BKN020-030 IF A ROGUE SHOWER CROSSES THE AREA. VISIBILITY
UNRESTRICTED. SURFACE WINDS WILL REMAIN S-SE 4-8 KT THROUGH THIS
EVENING. KAM

&&

.MARINE...THE SURFACE LOW FROM LAST NIGHTS COLD FRONT WILL REMAIN
ALONG THE B.C. COAST TODAY...MAINTAINING S FLOW ACROSS WA WATERS.
WINDS ARE ALREADY BELOW SCA LEVELS AND THE EXISTING SCA WILL BE
ALLOWED TO EXPIRE AT 10 AM.

THE NEXT FRONTAL SYSTEM OVER THE NE PACIFIC ALONG 140W AT 1630Z/830
AM WILL APPROACH THE REGION TONIGHT THE MOVE ACROSS THE AREA
FRIDAY/FRIDAY NIGHT. MODELS REMAIN FAIRLY CONSISTENT IN SHOWING
GALES OVER THE COASTAL WATERS STARTING FRIDAY AFTERNOON AND THE
USUAL SE EXPOSED AREAS OF THE NORTH INTERIOR WATERS STARTING LATE
FRIDAY AFTERNOON/FRIDAY EVENING.

WESTERLY FLOW ALOFT OVER THE NORTHEAST PACIFIC SATURDAY THROUGH
MONDAY WILL BRING SEVERAL WEAKER SURFACE TROUGHS ACROSS THE AREA.
SWELLS IN THE 15-20 FOOT RANGE ARE FORECAST TO REACH THE COAST
SUNDAY. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT CENTRAL STRAIT AND PUGET
     SOUND THIS MORNING.
     GALE WARNING COAST FRIDAY AFTERNOON AND EVENING.
     GALE WATCH EAST ENTRANCE AND NORTHERN INLAND WATERS FRIDAY
     AFTERNOON AND EVENING.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

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