Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 191025
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
325 AM PDT SAT APR 19 2014

.SYNOPSIS...A COLD FRONT WILL MOVE THROUGH THE AREA THIS AFTERNOON.
SHOWERS WILL FOLLOW THE FRONT TONIGHT THEN TAPER OFF EARLY SUNDAY
MORNING. THE NEXT APPROACHING FRONT WILL STALL OFF THE COAST ON
SUNDAY WITH JUST A CHANCE OF RAIN ALONG THE NORTH COAST. THE FRONT
WILL CONTINUE TO HAVE A HARD TIME MOVING EAST SUNDAY NIGHT INTO
MONDAY BEFORE MOVING THROUGH THE AREA MONDAY NIGHT. THE WEATHER WILL
REMAIN COOL AND UNSETTLED THROUGH THROUGH THE END OF NEXT WEEK.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS THE COLD FRONT OFFSHORE NEAR
129W AT 10Z/3AM. MID LEVEL CLOUD DECK OUT AHEAD OF THE FRONT IS
ALREADY SPREADING OVER WESTERN WASHINGTON. LANGLEY HILL DOPPLER
RADAR PICKING UP RAIN NEAR CAPE FLATTERY. OBSERVATIONS FROM KUIL NOT
REPORTING ANY RAIN YET. TEMPERATURES AT 3 AM WERE IN THE MID 30S TO
MID 40S.

RAIN OUT AHEAD OF THE FRONT SPREADING INLAND THIS MORNING WITH THE
LEADING EDGE OF THE PRECIPITATION MOVING INTO THE CASCADES BY NOON.
FRONT MOVING THROUGH THE AREA THIS AFTERNOON MAKING FOR A WET START
TO THE WEEKEND ACROSS WESTERN WASHINGTON. WITH ALL OF THE CLOUD
COVER AND PRECIPITATION HIGH TEMPERATURES IN THE 50S TODAY.

UPPER LEVEL TROUGH MOVING INLAND QUICKLY BEHIND THE FRONT LATE THIS
AFTERNOON AND THIS EVENING KEEPING SHOWERS IN THE FORECAST. PUGET
SOUND CONVERGENCE ZONE FORMING IN THE EVENING. WITH THE FLOW IN THE
LOWER LEVEL REMAINING SOUTHWESTERLY EXPECT THE CONVERGENCE ZONE TO
STAY IN SNOHOMISH AND SKAGIT COUNTIES INTO THE EARLY MORNING HOURS.
FOR THE REMAINDER OF THE AREA SHOWER ACTIVITY DECREASING OVERNIGHT
WITH A TRANSITORY UPPER LEVEL RIDGE JUST OFF THE COAST BY 12Z/5AM.
LOW TEMPERATURE WILL MOSTLY BE IN THE LOWER TO MID 40S.

SOME CHANGES TO THE FORECAST ON SUNDAY AS THE NEXT APPROACHING FRONT
STALLS OFF THE COAST DUE TO A DEEP UPPER LEVEL TROUGH DIGGING BACK
OUT BETWEEN 140-150W. FRONT NOT FAR ENOUGH TO THE WEST TO TAKE THE
CHANCE POPS OUT OF THE NORTH COAST AND THERE STILL COULD BE SOME
LINGERING CONVERGENCE ZONE SHOWERS IN THE NORTH CASCADES BUT OUTSIDE
OF THOSE AREAS HAVE GONE WITH A DRY FORECAST FOR SUNDAY. WITH THE
FRONT JUST OFFSHORE PLENTY OF MID LEVEL CLOUDS SO WILL WORD THE
FORECAST JUST PARTLY SUNNY FOR SUNDAY. WITH THE FRONT STALLING LOOK
FOR TEMPERATURES ON SUNDAY TO BE ABOUT 5 DEGREES WARMER VERSUS
SATURDAY...MID 50S TO MID 60S.

FRONT CONTINUING TO TO BECOME MORE NORTH SOUTH ORIENTED SUNDAY
NIGHT WITH THE DEEP UPPER LEVEL TROUGH MOVING EAST A BIT. THIS WILL
CONFINE THE THREAT OF RAIN TO THE NORTH COAST SUNDAY NIGHT. LOWS
WILL BE IN THE 40S.

FRONT CONTINUING TO STALL OFF THE COAST MONDAY WITH THE FLOW ALOFT
BECOMING MORE SOUTHERLY. AIR MASS BECOMING SOMEWHAT UNSTABLE IN THE
AFTERNOON ESPECIALLY OVER THE CASCADES SO EVEN THROUGH THE FRONT IS
STILL OFFSHORE WILL HAVE TO INCLUDE A CHANCE OF SHOWERS IN THE
FORECAST FOR THE ENTIRE AREA. HIGH TEMPERATURES ON MONDAY ARE A
LITTLE TRICKY WITH THE POSSIBLE CONVECTION IN THE AFTERNOON COMBINED
WITH THE FRONT JUST OFFSHORE. FOR NOW HAVE GONE PRETTY MUCH WITH
PERSISTENCE FOR THE HIGHS ON MONDAY...MID 50S TO MID 60S AGAIN.

WHAT IS LEFT OF THE FRONT MOVING INLAND MONDAY NIGHT WITH THE UPPER
LEVEL TROUGH OFFSHORE MOVING EAST OF 130W BY 12Z/5AM. WITH THE FRONT
WEAKENING HAVE GONE WITH SHOWERS AS THE PRECIPITATION TYPE. FELTON

.LONG TERM...EXTENDED MODELS ARE IN GOOD AGREEMENT WITH THE COOL
UPPER LEVEL TROUGH MOVING THROUGH ON TUESDAY. MODEL SOLUTION DIVERGE
ON WEDNESDAY WITH THE GFS TRYING TO DRY THINGS OUT WHILE THE
CANADIAN AND ECMWF CONTINUE THE CHANCE FOR SHOWERS. GOOD AGREEMENT
AGAIN ON THURSDAY WITH AN ORGANIZED FRONT MOVING THROUGH THE AREA
WITH AN UPPER LEVEL TROUGH OFFSHORE ON FRIDAY. CURRENT FORECAST HAS
CHANCE POPS THROUGH THE PERIOD EXCEPT ON THURSDAY WHERE LIKELY POPS
ARE IN THE FORECAST. SINCE THE ECMWF AND CANADIAN STILL HAVE
PRECIPITATION OVER THE AREA ON WEDNESDAY WILL STAY REFRAIN FROM
DRYING OUT WEDNESDAY AND STAY WITH THE CURRENT EXTENDED FORECAST.
FELTON

&&

.HYDROLOGY...RIVER FLOODING IS UNLIKELY FOR THE NEXT 7 DAYS.

THE EXCEPTION IS THE NORTH FORK OF THE STILLAGUAMISH RIVER EAST OF
THE SR 530 LANDSLIDE NEAR OSO WHERE A FLOOD WARNING REMAINS IN
EFFECT UNTIL FURTHER NOTICE. FLOODING CONTINUES FOR THIS RIVER AS A
RESULT OF WATER POOLED BEHIND THE DEBRIS DAM THAT PARTIALLY BLOCKS
THE RIVER.

AT 215 AM...THE NORTH FORK OF THE STILLAGUAMISH NEAR ARLINGTON IS AT
4.9 FT...OR 3240 CFS AND IS FALLING. IT IS EXPECTED TO FALL TO
AROUND 4.4 FT THIS AFTERNOON THEN RISE BACK UP TO AROUND 5.3 FEET
MIDDAY SUNDAY BEFORE RESUMING A FALL BACK DOWN TO AROUND 4 FT EARLY
NEXT WEEK. SIMILAR TRENDS ARE EXPECTED ON THE NORTH FORK OF THE
STILLAGUAMISH NEAR OSO AND AT THE SR 530 SLIDE POOL TO THE EAST OF
THE LANDSLIDE.  FELTON

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL MOVE THROUGH WRN WA THIS
AFTERNOON AND EVENING. THE ASSOCIATED SURFACE FRONT REACHES THE
COAST BY LATE MORNING...THEN PUSHES THROUGH INTERIOR WRN WA MIDDAY
TO EARLY AFTERNOON. MODERATE SW FLOW ALOFT. STABLE CONDITIONS.
BECOMING MOIST AT ALL LEVELS. RAIN ALONG THE COAST THIS
MORNING...SPREADING INLAND BY MIDDAY. CIGS ACROSS THE INTERIOR WILL
LOWER TO 3-5K FT AS RAIN DEVELOPS LATE THIS MORNING OR EARLY
AFTERNOON AHEAD OF THE FRONT. THE FRONT WILL PUSH THROUGH PUGET
SOUND ROUGHLY 20Z (1PM).

KSEA...SCT-BKN MID/HIGH CLOUDS EARLY...THEN CIGS 3-5K FT DEVELOPING
BY MID TO LATE MORNING. NE OR VARIABLE WINDS TO 5 KT...THEN SE 5-10
KT AFTER 12Z...BECOMING SW 10-15 W/ GUSTS TO 22 KT AFTER 20Z. RAIN
DEVELOPING BY MIDDAY. DTM

&&

.MARINE...A COLD FRONT MOVING INTO THE COASTAL WATERS THIS MORNING
WILL PUSH ACROSS THE INLAND WATERS MIDDAY TO EARLY AFTERNOON. SMALL
CRAFT ADVISORY WINDS ARE EXPECTED OVER ALL WATERS. HIGH PRESSURE
WILL REBUILD ON SUNDAY. A WEAKER SYSTEM WILL ARRIVE LATER MONDAY OR
MONDAY NIGHT.

A LARGE SWELL TRAIN WILL ARRIVE ALONG THE WASHINGTON COAST THIS
EVENING AND CONTINUE INTO SUNDAY. LARGE WAVES UP TO 15 FEET WILL
IMPACT THIS COAST BY THIS EVENING...BUILDING TO 16 TO 19 FEET LATER
TONIGHT INTO SUNDAY MORNING. A HIGH SURF ADVISORY IS IN EFFECT FOR
THE COAST FROM THIS EVENING THROUGH SUNDAY. THIS IS A RAZOR CLAM DIG
WEEKEND FOR TWIN HARBORS...COPALIS AND MOCLIPS BEACHES. EXTREME
CAUTION SHOULD BE EXERCISED AS WAVES WILL LIKELY RACE FURTHER UP THE
BEACH THAN NORMAL.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNING REMAINS IN EFFECT FOR THE NORTH FORK OF THE
     STILLAGUAMISH RIVER EAST OF THE SR 530 LANDSLIDE.
     HIGH SURF ADVISORY NORTH AND CENTRAL COAST THIS EVENING THROUGH
     SUNDAY AFTERNOON.

PZ...SMALL CRAFT ADVISORY ALL WATERS THROUGH THIS EVENING.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT.


&&

$$

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