Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 031710
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 AM PST WED FEB 3 2016

.SYNOPSIS...A FRONT JUST OFF THE COAST WILL BRING RAIN AND
MOUNTAIN SNOW TO WESTERN WASHINGTON THROUGH TONIGHT. SHOWERS WILL
FOLLOW THE FRONT THURSDAY AND TAPER OFF THURSDAY NIGHT. A STRONGER
FRONTAL SYSTEM WILL MOVE THROUGH FRIDAY AND FRIDAY NIGHT FOR RAINY
WINDY WEATHER. SHOWERS WILL LINGER SATURDAY...AND A STRONG UPPER
RIDGE SHOULD BRING DRY MILD WEATHER SUNDAY THROUGH TUESDAY.

&&

.SHORT TERM...A SMALL UPPER RIDGE IS OVER THE PACIFIC NORTHWEST
THIS MORNING. AN INCOMING FRONTAL SYSTEM JUST OFFSHORE...AND THE
LEADING EDGE OF RAIN JUST REACHED THE WASHINGTON COAST IN THE
LAST HOUR. ELSEWHERE SKIES ARE CLOUDY ACROSS WESTERN WASHINGTON
WITH 8 AM TEMPERATURES IN THE UPPER 30S TO MID 40S.

THE UPPER RIDGE WILL MOVE ACROSS EASTERN WASHINGTON TODAY...AND
THE FRONTAL SYSTEM WILL MOVE INTO OUR FORECAST AREA WITH
PRECIPITATION SPREADING TO THE CASCADE CREST THIS AFTERNOON. THE
COLD FRONT WILL CROSS THE AREA THIS EVENING...FOLLOWED QUICKLY BY
THE UPPER TROUGH. THE FRONT WILL BRING BREEZY TO WINDY CONDITIONS
TO THE NORTH INTERIOR AND COAST.

FORECAST PRECIPITATION AMOUNTS HAVE CHANGED LITTLE WITH GENERALLY
UP TO A HALF INCH FOR THE INTERIOR LOWLANDS...A HALF INCH TO AN
INCH AT THE COAST...AND A HALF INCH TO ONE AND A HALF INCHES
COMMON IN THE MOUNTAINS. THE SNOW LEVEL WILL BE 1500 TO 2500 FT
TODAY AND RISE TO AROUND 3000 FT TONIGHT...REMAINING AT OR BELOW
HIGHWAY PASS LEVELS FOR THE DURATION OF THE EVENT. A WINTER
WEATHER ADVISORY REMAINS IN EFFECT THROUGH THURSDAY MORNING FOR
THE LIKELIHOOD OF 6 TO 16 INCHES OF SNOW.

AN UPPER RIDGE WILL START BUILDING INTO THE PACIFIC NORTHWEST
THURSDAY. SCATTERED SHOWERS WILL CONTINUE THOUGH -- INITIALLY DUE
TO MOIST ONSHORE LOW LEVEL FLOW AND SHALLOW INSTABILITY...AND THEN
FROM THE SOUTHERN END OF A WEAK WARM FRONT MOVING INTO COASTAL
BRITISH COLUMBIA. THERE SHOULD BE SOME BRIEF DRYING THURSDAY NIGHT
AS THE RIDGE BUILDS FURTHER.

A STRONGER...WARMER...AND WETTER FRONTAL SYSTEM WILL MOVE THROUGH
THE FORECAST AREA FRIDAY AND FRIDAY NIGHT. THE GFS AND ECMWF HAVE
COME INTO BETTER AGREEMENT ON THE TIMING OF THIS SYSTEM. IT WILL
BRING WINDY CONDITIONS AGAIN TO THE COAST AND NORTH INTERIOR --
MORE LIKELY IN THE ADVISORY WIND RANGE AND ISOLATED HIGH WIND
REPORTS IN THE NORTH INTERIOR ARE POSSIBLE.

BRIEF PERIODS OF MODERATE TO HEAVY PRECIPITATION ARE LIKELY
FRIDAY AFTERNOON AND EVENING...ESPECIALLY ON SOUTHWEST FACING
SLOPES OF THE MOUNTAINS WITH 850 MB WINDS AROUND 60 KT AND THE
SNOW LEVEL REACHING 5000 TO 6000 FT. TOTAL PRECIPITATION WILL
PROBABLY BE 0.25 TO 0.75 INCH FOR THE INTERIOR LOWLANDS...WITH 0.5
TO 1.5 INCHES AT THE COAST...AND 1 TO 2.5 INCHES IN THE MOUNTAINS.
THE SNOW LEVEL WILL FALL TO 2500 TO 3000 FT LATE FRIDAY NIGHT.
MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE EARLY MORNING
FORECAST DISCUSSION -- THE GFS/ECMWF MAINTAIN STRONGER NW FLOW
OVER WRN WA INTO SATURDAY BUT WANING THROUGH THE DAY. SNOW IN THE
MOUNTAINS AND SHOWERS OVER THE LOWLANDS SHOULD DECREASE. IT COULD
BE DRY OVER THE LOWLANDS BY AFTERNOON DEPENDING ON HOW QUICKLY THE
RIDGE STARTS TO BUILD BUT THIS REMAINS UNCERTAIN. MODELS DO AGREE
THAT THE UPPER RIDGE AMPLIFIES AND BUILDS OVER THE REGION
SUNDAY...PERSISTING THROUGH TUESDAY OF NEXT WEEK. THIS WOULD GIVE
A PERIOD OF MILD OFFSHORE FLOW WITH SUNSHINE AND POSSIBLY
TEMPERATURES REACHING THE UPPER 50S.

&&

.AVIATION...COLD FRONTAL PASSAGE EXPECTED ALONG THE COAST AROUND
00Z...THEN OVER THE INTERIOR AROUND 02Z. UNTIL FROPA...RAIN WILL
INCREASE WITH VSBYS SLOWLY COMING DOWN...BUT AN EASTERLY COMPONENT
TO SFC WIND WILL KEEP CIGS AOA 030 FOR I-5 CORRIDOR TAF SITES.
FOLLOWING FROPA...SW WINDS WILL BRING IN LOW-LEVEL MOISTURE FROM
THE PACIFIC...CAUSING CIGS TO FALL. HOWEVER...RAIN WILL LIGHTEN
UP...SO SFC VSBYS WILL IMPROVE.

KSEA...COLD FRONTAL PASSAGE (FROPA) EXPECTED AROUND 02Z...OR 6
PM. RAIN WILL STEADILY PICK UP THIS AFTN IN ADVANCE OF THE
FRONT...WITH A PERIOD OF VSBYS BELOW 6SM IN THE 2-3 HOURS BEFORE
FROPA. CIGS WILL STEADILY COME DOWN AS WELL...BUT THEY SHOULD
REMAIN AOA 030 UNTIL FROPA. AFTER FROPA...RAIN WILL TAPER
OFF...AND SFC VSBY WILL IMPROVE...BUT MOISTER AIR NEAR THE SFC
WILL ARRIVE FROM THE PACIFIC...SO CIGS WILL DROP TO NEAR 020 SOON
AFTER FROPA. SE WIND TIL FROPA...SHIFTING OUT OF THE SW DURING
FROPA. WINDS AT 050 PEAK NEAR 45 KT OUT OF THE SW AROUND 00Z-
02Z...WHILE WINDS AT 020 PEAK NEAR 35 KNOTS DURING THE SAME TIME
BEFORE THE FROPA.HANER

&&

.MARINE...A COLD FRONT WILL MOVE FROM WEST TO EAST ACROSS THE
WATERS DURING THE AFTERNOON AND EARLY EVENING. STRONG E-SE
GRADIENTS PRECEDE THE FRONT...WITH GALES EXPECTED FOR THE SE-WIND
PRONE COAST AND EAST ENTRANCE ZONES. THE FRONT WILL ARRIVE AT THE
COASTLINE AROUND 4 PM...THEN CROSS THE INLAND WATERS AROUND 6 PM.
FOLLOWING THE FRONT...A FEW HOURS OF SMALL CRAFT WESTERLY WINDS
ARE EXPECTED IN THE CENTRAL AND EASTERN STRAIT. ENOUGH SW GRADIENT
WILL OCCUR FOR SOME SMALL CRAFT WINDS IN PUGET SOUND AND THE
NORTHERN INLAND WATERS. LIGHTER WINDS ARE EXPECTED THURSDAY AS A
WEAK RIDGE OF HIGH PRES MOVES ACROSS THE AREA.

A STRONGER FRONTAL SYSTEM WILL MOVE INTO THE COASTAL WATERS ON
FRIDAY. GALES ARE EXPECTED AHEAD OF FRIDAYS FRONT OVER THE
COASTAL WATERS AND MAY OCCUR AT THE ENTRANCES TO THE STRAIT AND IN
THE NORTHERN INLAND WATERS. OTHER WATERS WILL LIKELY SEE SMALL
CRAFT ADVISORY CONDITIONS.

SOMEWHAT ENERGETIC WAVES BEING DEVELOPED SOUTH OF A LOW WELL
OFFSHORE WILL REACH THE WASHINGTON COAST TONIGHT AND WILL CONTINUE
THROUGH THURSDAY. THESE WAVES OF 15 TO 18 FT AT 19 OR
20 SECONDS WILL LIKELY CAUSE FURTHER BEACH EROSION ON SENSITIVE
BEACHES FROM WESTPORT TO OCEAN SHORES. ANOTHER ROUND OF HIGH
WAVES... BUILDING TO AROUND 20 FEET...IS EXPECTED LATER FRIDAY
INTO FRIDAY NIGHT. THE SWELL WILL SUBSIDE ON SATURDAY. SWELL THIS
LARGE HAVE THE POTENTIAL TO CAUSE MORE BEACH EROSION PROBLEMS
ALONG THE WASHINGTON COAST ESPECIALLY IN WESTPORT AND OCEAN
SHORES. HANER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THE NEXT 7 DAYS. THE
FRONTAL SYSTEM THAT MOVES THROUGH THE AREA FRIDAY AND FRIDAY NIGHT
WILL PRODUCE 1.0 TO 2.5 INCHES OF PRECIPITATION OVER THE
OLYMPICS...MOST OF THAT FALLING IN AROUND 12 HOURS WITH THE SNOW
LEVEL AROUND 6000 FT. WE WILL NEED TO SEE HOW THE MODELS FORECAST
THIS SYSTEM OVER THE NEXT FEW DAYS...BUT AT THIS TIME EVEN THE
SKOKOMISH RIVER LOOKS UNLIKELY TO FLOOD. MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY FROM NOON TODAY TO NOON PST THURSDAY FOR
     CASCADES OF PIERCE AND LEWIS COUNTIES-CASCADES OF SNOHOMISH
     AND KING COUNTIES-CASCADES OF WHATCOM AND SKAGIT COUNTIES.

     HIGH SURF ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM PST THURSDAY
     FOR CENTRAL COAST.

PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR FROM 6 PM THIS EVENING TO 6
     PM PST THURSDAY FOR GRAYS HARBOR BAR.

     GALE WARNING UNTIL 4 PM PST THIS AFTERNOON FOR COASTAL WATERS
     FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL
     WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 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 FOR HAZARDOUS SEAS FROM 4 PM THIS AFTERNOON
     TO 6 PM PST THURSDAY FOR COASTAL WATERS FROM CAPE FLATTERY
     TO JAMES ISLAND OUT 10 NM-COASTAL WATERS FROM JAMES ISLAND
     TO POINT GRENVILLE OUT 10 NM-COASTAL WATERS FROM POINT
     GRENVILLE TO CAPE SHOALWATER OUT 10 NM.

     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM PST
     THURSDAY 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 POINT
     GRENVILLE TO CAPE SHOALWATER 10 TO 60 NM.

     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 1 AM PST THURSDAY
     FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST
     ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     GALE WARNING UNTIL 6 PM PST THIS EVENING FOR CENTRAL U.S. WATERS
     STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS STRAIT OF
     JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 1 AM PST THURSDAY FOR NORTHERN INLAND
     WATERS INCLUDING THE SAN JUAN ISLANDS.

     SMALL CRAFT ADVISORY UNTIL 6 PM PST THIS EVENING FOR ADMIRALTY
     INLET-WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 6 PM THIS EVENING
     TO 6 PM PST THURSDAY FOR WEST ENTRANCE U.S. WATERS STRAIT
     OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO NOON PST THURSDAY
     FOR PUGET SOUND AND HOOD CANAL.

&&

$$

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