Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 171617
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PDT FRI OCT 17 2014

.SYNOPSIS...RAIN AND LOCALLY WINDY CONDITIONS WILL SPREAD FROM THE
COAST INTO THE INTERIOR THIS AFTERNOON AND THIS EVENING AS A COLD
FRONT MOVES ACROSS THE AREA. PRECIPITATION WILL TAPER TO SHOWERS
LATE TONIGHT THEN COME TO AN END SATURDAY MORNING AS HIGH PRESSURE
BUILDS. AN UPPER LEVEL RIDGE AND OFFSHORE FLOW WILL BRING PARTLY
SUNNY AND WARMER WEATHER ON SUNDAY. A SERIES OF FRONTS WILL GIVE
PERIODS OF RAIN AND WINDY CONDITIONS AT TIMES NEXT WEEK.

&&

.SHORT TERM...RADAR AND OBSERVATIONS SHOW WIDESPREAD LIGHT RAIN OVER
WESTERN WASHINGTON THIS MORNING. HAVE ALREADY UPDATED THE GRIDS AND
ZONES FOR RAIN AT TIMES OVER THE INTERIOR. THIS RAIN WILL CONTINUE
THROUGH THE DAY INTO THE EVENING BEFORE TURNING TO SHOWERS. NOT MUCH
WIND NOTED WITH THIS SYSTEM YET OVER LAND AREAS THOUGH THE COASTAL
WATERS ARE EXPERIENCING A SOLID GALE. AS THE FRONT MOVES INLAND THIS
EVENING THERE SHOULD BE A PERIOD OF WINDY CONDITIONS ON THE COAST
AND OVER THE NORTH INTERIOR.

MODELS SHOW ONLY A LITTLE RAIN OVER THE MOUNTAINS ON SATURDAY WITH
LOWLAND AREAS MOSTLY DRY. THERE SHOULD BE AT LEAST SOME SUN IN THE
AFTERNOON AS WELL. HIGHS WILL BE IN THE 60S BOTH TODAY AND SATURDAY
BUT TOMORROW SHOULD BE A FEW DEGREES WARMER.

SUNDAY MORNING WILL ALSO HAVE SOME SUN OVER THE INTERIOR BUT ANOTHER
FRONT WILL REACH THE COAST IN THE AFTERNOON. MIGHT SEE A FEW SPOTS
NEAR 70 OVER THE INTERIOR BUT THE CLOUDY AND THEN RAINY COAST WILL
NOT GET OUT OF THE 60S. BURKE

.LONG TERM...PREVIOUS DISCUSSION...MONDAY AND TUESDAY WILL BE
SHOWERY AS THE UPPER TROUGH ASSOCIATED WITH SUNDAY NIGHTS FRONT
MOVES ACROSS THE AREA.

A BIG CHANGE TO A VERY RAINY AND WINDY PATTERN WILL TAKE PLACE
TUESDAY NIGHT AND WILL CONTINUE THROUGH MUCH OF NEXT WEEK. THE
SYSTEM CAUSING THE CHANGE IS CURRENTLY IN THE WEST PACIFIC OFF OF
KAMCHATKA. ALL GLOBAL MODELS SHOW THIS STRONG SYSTEM ENTRAINING
MOISTURE FROM THE REMNANTS OF TROPICAL STORM/HURRICANE ANA NOW
APPROACHING THE HAWAIIAN ISLANDS. GIVEN THE SOURCE OF THE AIR
MASS...TEMPERATURES AND DEWPOINT TEMPERATURES IN THE EXTENDED
FORECAST PERIOD FROM TUESDAY NIGHT THROUGH THURSDAY WERE RAISED
SEVERAL DEGREES. POPS WILL BE HIGH THROUGH THE PERIOD...AND IT WILL
LIKELY BE WINDY AT TIMES...ESPECIALLY ALONG THE COAST AND IN THE
NORTH INTERIOR. SNOW LEVELS ARE EXPECTED TO BE RATHER HIGH...8000
FEET OR HIGHER...WEDNESDAY AND THURSDAY. ALBRECHT

&&

.HYDROLOGY...PREVIOUS DISCUSSION...LOCALLY HEAVY RAINFALL ALONG THE
COAST AND ON THE WEST SLOPES OF THE OLYMPICS THIS AFTERNOON AND
EVENING WILL RESULT IN RISES ON COASTAL RIVERS. BUT FLOODING IS NOT
EXPECTED.

AFTER A PERIOD OF RELATIVELY DRY WEATHER...ANOTHER ROUND OF RAINFALL
IS EXPECTED SUNDAY NIGHT THROUGH TUESDAY. THIS RAINFALL IS NOT
EXPECTED TO BE HYDROLOGICALLY SIGNIFICANT.

GLOBAL MODELS AND THEIR ENSEMBLES ARE STRONGLY SUGGESTING THAT AN
ATMOSPHERIC RIVER EVENT WILL SET UP SOMEWHERE BETWEEN NW WASHINGTON
(CANADIAN AND ECMWF MODELS) AND CENTRAL OREGON (GFS) WEDNESDAY
THROUGH FRIDAY OF NEXT WEEK...AND SEVERAL INCHES OF RAIN CAN BE
EXPECTED IN A 24 HOUR PERIOD WHEREVER THE PATTERN SETS UP. THE FIRE
HOSE MAY (GFS) OR MAY NOT (CANADIAN AND ECMWF) WAVE SOUTH AND NORTH
ACROSS THE AREA DURING THIS PERIOD. THERE IS A GOOD DEAL OF
UNCERTAINTY AT THIS RANGE...BUT FLOODING IS POSSIBLE ON SOME RIVERS
ACROSS WESTERN WASHINGTON TOWARD THE MIDDLE OR END OF NEXT WEEK IF
THE CANADIAN OR ECMWF SOLUTIONS VERIFY. ALBRECHT

&&

.AVIATION...A WEAKENING COLD FRONT WILL MOVE INLAND ACROSS WESTERN
WA THIS EVNG. MODERATE TO STRONG SLY FLOW ALOFT WILL SHIFT TO SWLY
BEHIND THE FRONT AND THEN WEAKEN OVERNIGHT. THE AIR MASS WILL BE
MOIST AND STABLE. FAIRLY WIDESPREAD RAIN THIS AFTN WILL BECOME LESS
WIDESPREAD AND MORE SHOWERY THIS EVNG. EASTERLY SFC FLOW IS KEEPING
CIGS THIS MORNING UP IN THE VFR CATEGORY FOR MOST...BUT A WEAKENING
OF THE EASTERLY COMPONENT THIS EVNG WILL ALLOW CIGS TO FALL STARTING
THIS EVNG...WITH IFR CONDS PREVAILING BY SUNRISE ON SAT. DURING THE
DAY SAT...LARGE-SCALE LIFT WILL BE LARGELY ABSENT...BUT THE AIR MASS
WILL REMAIN MOIST. WOULD EXPECT A FEW MORE BREAKS IN THE CLOUDS AND
A LACK OF RAIN ON SAT...BUT BKN CIGS IN MVFR RANGES WILL PERSIST AT
MANY WRN WA LOCALES ON SAT AFTN.

KSEA...RAIN WILL BECOME HEAVIER AND MORE WIDESPREAD THIS AFTN...BUT
DRYING EASTERLY FLOW AT THE SURFACE WILL KEEP CIGS UP IN THE 050-060
RANGE FOR MOST OF THE AFTN WITH VSBYS AOA 6SM. EASTERLY COMPONENT TO
THE SFC WIND WILL WEAKEN AFT 00Z...SO CIGS WILL HAVE THE OPPORTUNITY
TO FALL BLO 050 ARND 00Z. CIGS WILL CONTINUE TO FALL THROUGH THE
NIGHT AS WINDS ALOFT GRADUALLY VEER FROM SOUTHERLY TO
SOUTHWESTERLY...WITH CIGS POSSIBLY BELOW 010 FROM 12Z-17Z ON SAT
MORNING.    HANER

&&

.MARINE...983 MB SFC LOW NEAR THE WEST COAST OF HAIDA GWAII IS
LIFTING NORTH AND FILLING THIS MORNING. A COLD FRONT IS TRAILING
SOUTH ALONG 130W...RESULTING IN MAINLY EAST-SOUTHEAST PRESSURE
GRADIENTS OVER THE WATERS THIS MORNING. LA PUSH RECENTLY REPORTED 34
KT WIND...AND HARO STRAIT JUMPED TO 34 KT THIS PAST HOUR AS WELL.
THE TREND WILL BE TOWARD INCREASING E-SE WIND UNTIL MID-AFTERNOON.
THE COLD FRONT ALONG 130W WILL MAKE HEADWAY TOWARD THE COAST THIS
AFTN AND MOVE INLAND THIS EVNG...BUT THE FRONT WILL BE WEAKENING AND
FILLING ALONG THE WAY. AS THE FRONT MOVES INLAND THIS EVNG...
GRADIENTS WILL TRANSITION FROM MODERATE EASTERLY TO WEAKER
SOUTHEASTERLY. WINDS IN GENERAL WILL EASE THIS EVNG...AND SE
GRADIENTS DO NOT FAVOR A PUSH OF WIND INTO PUGET SOUND. COMBINED
SEAS ARE BUILDING TO OVER 15 FT OVER THE COASTAL WATERS.

SURFACE HIGH PRESSURE BUILDS OVER THE WATERS ON SAT AS THE LOW
PRESSURE SYSTEM EXITS THE REGION. THE NEXT FRONT WILL ENTER THE
COASTAL WATERS SUN AFTERNOON AND AFFECT THE AREA THROUGH MON.
ADDITIONAL FRONTS WILL AFFECT THE WATERS THE REMAINDER OF NEXT WEEK.
HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...

PZ...GALE WARNING COAST...ENTRANCES...AND NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY CENTRAL STRAIT AND ADMIRALTY INLET.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

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