Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 230401
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT TUE APR 22 2014

.SYNOPSIS...A COLD FRONT WILL BRING SHOWERS TONIGHT. A WARM FRONT
WILL SPREAD RAIN INTO WESTERN WASHINGTON WEDNESDAY AFTERNOON THROUGH
WEDNESDAY NIGHT. A SECOND COLD FRONT WILL THEN SHIFT INLAND THURSDAY
MORNING. AN UPPER LEVEL TROUGH WILL CROSS THE REGION ON FRIDAY FOR
SCATTERED SHOWERS. A THIRD FRONTAL SYSTEM WILL BRING RAIN TO THE
AREA THIS WEEKEND.

&&

.SHORT TERM...SHOWERS WILL BE NUMEROUS THIS EVENING AS AN UPPER
SHORT WAVE MOVES ONSHORE. THEY WILL PROBABLY TAPER A BIT AFTER
MIDNIGHT AS THE UPPER LEVEL DISTURBANCE MOVES EAST OF THE AREA.

AFTER A BIT OF A BREAK FOR THE FIRST PART OF WEDNESDAY...RAIN WILL
INCREASE FROM THE SOUTHWEST LATE IN THE DAY AS A WARM FRONT MOVES
INTO THE AREA. THE WARM FRONT/COLD FRONT COMBO WILL MOVE ONSHORE
WEDNESDAY NIGHT/THURSDAY MORNING FOR A PERIOD OF RAIN ALL AREAS.

THURSDAY WILL SEE SHOWERS BEHIND THE FRONT WITH MOIST AND SOMEWHAT
UNSTABLE SOUTHWEST FLOW ALOFT. SOUTHERLY SURFACE GRADIENTS WILL BE
PRETTY STRONG BEHIND THE FRONT FOR SOME BREEZY WINDS.

AN UPPER TROUGH WILL SETTLE OVER THE PACIFIC NORTHWEST ON FRIDAY FOR
A CONTINUED CHANCE OF SHOWERS. MOST OF THE FLOW ALOFT WILL BE FAR TO
THE SOUTH AND SHOWERS WILL BE SPOTTY AND NOT TOO ORGANIZED. THERE
SHOULD BE A DECENT AMOUNT OF SUNSHINE IN BETWEEN SHOWERS. SCHNEIDER

.LONG TERM...PREVIOUS DISCUSSION...AN UPPER LEVEL TROUGH OVER THE
PAC NW WILL LEAD TO A FEW MORE SHOWERS ACROSS WESTERN WA ON
SATURDAY. OUR NEXT FRONTAL SYSTEM WILL THEN MOVE INLAND SATURDAY
NIGHT FOR A WETTER PERIOD OF WEATHER. ONSHORE FLOW WILL CONTINUE ON
SUNDAY WITH ZONAL FLOW ALOFT - SHOWERS WILL MAINLY AFFECT THE COAST
AND IN THE MOUNTAINS.

ANOTHER PAC FRONTAL SYSTEM WILL CROSS THE REGION MON OR MON NIGHT.
AN UPPER LEVEL RIDGE WILL BUILD OVER THE PAC NW ON TUE FOR DRIER AND
WARMER WEATHER. 33

&&

.HYDROLOGY...RIVER FLOODING REMAINS 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.

A FRONT WEDNESDAY NIGHT THROUGH THURSDAY COULD GIVE 1.00 INCH OF
RAIN. IF THIS OCCURS...THE NORTH FORK OF THE STILLAGUAMISH RIVER IN
THE SLIDE AREA WILL SEE MORE SIGNIFICANT RISES THAN WHAT ARE
CURRENTLY INDICATED IN THE RIVER FORECASTS.

AT 8 PM...THE NORTH FORK OF THE STILLAGUAMISH NEAR ARLINGTON WAS AT
4.7 FT...OR 2880 CFS. THE NORTH FORK OF THE STILLAGUAMISH RIVER NEAR
OSO WAS AT 216.7 FT AT 2050 CFS. THE POOL EAST OF THE SLIDE WAS
282.7 FT AT 6 PM THIS EVENING.

&&

.AVIATION...AN UPPER LEVEL AND SURFACE TROUGH WILL MOVE THROUGH WRN
WA TONIGHT. THERE WILL BE A BREAK BETWEEN SYSTEMS WEDNESDAY
MORNING...THEN ANOTHER TROUGH ARRIVES WEDNESDAY AFTERNOON AND
WEDNESDAY NIGHT. MODERATE SW FLOW ALOFT. MOIST AND SOMEWHAT UNSTABLE
THROUGH WEDNESDAY. SHOWERS...DECREASING LATE TONIGHT...INCREASING
WEDNESDAY AFTERNOON. A MIX OF VFR AND 2-4K FT MVFR CEILINGS.
WEDNESDAY SHOULD HAVE MOSTLY VFR CONDITIONS.

KSEA...CIGS VARIABLE BUT GENERALLY VFR...EXCEPT 2-3K FT CIGS WITH
SHOWERS THROUGH 12. GUSTY SOUTHWEST WINDS 8-12 KT...EASING TO 4-8 KT
AFTER MIDNIGHT.

&&

.MARINE...A SURFACE TROUGH WILL SLOWLY MOVE THROUGH THE WATERS
TONIGHT. HAVE EXTENDED THE SMALL CRAFT ADVISORY THROUGH 5 AM PDT AND
INCLUDES ALL WATERS EXCEPT THE CENTRAL STRAIT. WINDS SHOULD EASE
WEDNESDAY MORNING...THEN INCREASE LATE WEDNESDAY AFTERNOON EVENING
AHEAD OF THE NEXT SYSTEM ARRIVING THURSDAY. THIS ONE LOOKS STRONGER
SO SMALL CRAFT ADVISORY STRENGTH WINDS ARE LIKELY OVER MOST WATERS.
ANOTHER FRONT WILL ARRIVE ABOUT SATURDAY. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNING REMAINS IN EFFECT FOR THE NORTH FORK OF THE
     STILLAGUAMISH RIVER EAST OF THE SR 530 LANDSLIDE.

PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT CENTRAL STRAIT.

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML   (ALL LOWERCASE)








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