Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 161617
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PDT WED APR 16 2014

.SYNOPSIS...A WARM FRONT WILL STALL OVER THE REGION TODAY FOR RAIN
AT TIMES. A COLD FRONT WILL CROSS WESTERN WASHINGTON ON THURSDAY.
DRIER WEATHER IS FORECAST ON FRIDAY WITH WEAK HIGH PRESSURE
OVERHEAD. THE NEXT FRONT WILL ARRIVE LATER SATURDAY.

&&

.SHORT TERM...MOISTURE WILL CONTINUE TO STREAM OVER THE AREA FROM
THE WEST TODAY WITH WARM ADVECTION PROVIDING SOME LIFT AND GIVING
RAIN AT TIMES. THERE MAY BE A BRIEF LULL IN THE PRECIPITATION FOR
SOME AREAS THIS EVENING AHEAD OF AN APPROACHING FRONTAL SYSTEM. THIS
FRONTAL SYSTEM WILL BRING ANOTHER GOOD SHOT OF RAIN TO THE AREA
LATER TONIGHT AND THURSDAY WITH RAIN CHANGING TO SHOWERS LATE IN THE
DAY. IT WILL PROBABLY BE BREEZY MOST AREAS THURSDAY EVENING BEHIND
THE FRONT IN STRONG ONSHORE FLOW. SHOWERS WILL TAPER THURSDAY
NIGHT...MOSTLY CONFINED TO A PUGET SOUND CONVERGENCE ZONE AND OVER
THE MOUNTAINS AFTER MIDNIGHT. FRIDAY LOOKS LIKE A MAINLY DRY DAY
WITH WEAK HIGH PRESSURE IN CONTROL. SCHNEIDER

.LONG TERM...OVERALL CONFIDENCE IN THE LONG TERM PERIOD REMAINS LOW
AS THE MODELS ARE STILL NOT ALIGNED. THE GENERAL PATTERN CONSISTS OF
AN UPPER LOW OVER THE NE PAC WITH A SERIES OF FRONTS CROSSING
WESTERN WA. BUT THE EXACT TIMING OF EACH SYSTEM IS STILL UNCLEAR.
THEREFORE WILL NOT MAKE ANY WIDESPREAD CHANGES FROM THE PREVIOUS
FORECAST. 33

&&

.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.

THE NORTH FORK OF THE STILLAGUAMISH NEAR ARLINGTON IS FORECAST TO
RISE ABOUT A FOOT TODAY...THEN RISE AN ADDITIONAL FOUR FEET ON
THURSDAY WITH A CREST CLOSE TO 9 FEET. THE RIVER LEVEL WILL BEGIN
FALLING LATER THURSDAY NIGHT AND CONTINUE FALLING FRIDAY AS HIGH
PRESSURE MOVES OVER THE AREA.

TOTAL RAINFALL FOR THE SLIDE AREA THROUGH THURSDAY NIGHT WILL BE ON
THE ORDER OF TWO INCHES.

ADDITIONAL FRONTS WILL AFFECT THE SLIDE AREA LATER SATURDAY AND
MONDAY. THESE SYSTEMS ARE NOT EXPECTED TO BE ESPECIALLY WET OR
HYDROLOGICALLY SIGNIFICANT BUT THEY WILL KEEP CONDITIONS WET.

&&

.AVIATION...AN UPPER RIDGE WILL PREVAIL OVER THE REGION THRU
TONIGHT. CONTD STRONG WLY FLOW ALOFT. THE LOW LEVEL FLOW WILL REMAIN
SLY OR ONSHORE. THE AIR MASS WILL REMAIN MOIST BUT STABLE.
ANTICIPATE WIDESPREAD CIGS IN THE 1-3K FT RANGE ALONG WITH AREAS OF
VSBYS IN THE 3-5SM RANGE DUE TO RAIN AND/OR FOG. THE MTNS WILL BE
OBSCD.

KSEA...FOR THE MOST PART...EXPECT CIGS TO BE MAINLY IN THE 1500 TO
2500 FT RANGE TODAY. EXPECT OCNL VFR CIGS /AOB 4K FT/ DURING THE
DAY. WINDS WILL BE SLY 8-13 KNOTS.

&&

.MARINE...ONSHORE OR SOUTHERLY FLOW WILL PREVAIL ACROSS THE AREA
THROUGH TONIGHT. EXPECT A COLD FRONT TO MOVE ACROSS THE REGION ON
THU. HIGH PRES ALONG THE WASHINGTON COAST AND LOWER PRES E OF THE
CASCADES WILL RESULT IN LIGHT ONSHORE OR WESTERLY FLOW ON FRI.

&&

.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...NONE.

&&

$$

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