Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 162201
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT WED APR 16 2014

.SYNOPSIS...A FRONTAL SYSTEM WILL BRING RAIN TONIGHT AND THURSDAY.
DRIER WEATHER IS FORECAST ON FRIDAY WITH WEAK HIGH PRESSURE
OVERHEAD. ADDITIONAL FRONTS WILL ARRIVE LATER SATURDAY AND LATER
SUNDAY...KEEPING THE WEATHER GENERALLY WET. AN UPPER TROUGH WILL
BRING SHOWERY WEATHER EARLY NEXT WEEK.

&&

.SHORT TERM...A FRONTAL SYSTEM WILL MOVE ONSHORE TONIGHT AND
THURSDAY...WITH A WARM FRONT LATER TONIGHT...THEN A COLD FRONT
THURSDAY. THIS FRONTAL SYSTEM WILL BRING A GOOD SHOT OF RAIN TO THE
AREA TONIGHT AND THURSDAY WITH RAIN CHANGING TO SHOWERS LATE
THURSDAY. THE HIGHEST PARTS OF THE MOUNTAINS WILL GET SEVERAL INCHES
OF NEW SNOW BUT SNOW LEVELS WILL BE A LITTLE TOO HIGH FOR MUCH SNOW
IN THE PASSES OR  ROADS UP TO THE SKI AREAS.

IT WILL BE BREEZY MOST AREAS THURSDAY EVENING BEHIND THE FRONT IN
STRONG ONSHORE FLOW. SHOWERS WILL TAPER THURSDAY NIGHT...AND BECOME
MOSTLY CONFINED TO A PUGET SOUND CONVERGENCE ZONE AND OVER THE
MOUNTAINS AFTER MIDNIGHT. FRIDAY THROUGH SATURDAY MORNING LOOKS LIKE
A DRY PERIOD WITH WEAK HIGH PRESSURE IN CONTROL. A SECOND FRONT WILL
APPROACH FROM THE WEST ON SATURDAY...WITH RAIN REACHING THE COAST
AROUND MIDDAY...THEN SPREADING INLAND DURING THE AFTERNOON. SCHNEIDER

.LONG TERM...RAIN WILL CHANGE TO SHOWERS SATURDAY NIGHT AS A FRONT
MOVES INLAND. ANOTHER FRONT WILL REACH THE AREA LATER SUNDAY...THEN
A LARGE UPPER TROUGH WILL SETTLE OVER THE PACIFIC NORTHWEST ON
MONDAY FOR SHOWERY WEATHER. THERE IS A SUGGESTION IN THE MODELS THAT
WEAK HIGH PRESSURE ALOFT WILL BRING DRIER WEATHER IN THE MIDDLE OF
NEXT WEEK. SCHNEIDER

THERE IS A POSSIBILITY OF HIGH SURF CONDITIONS ON THE COAST LATE
SATURDAY NIGHT THROUGH SUNDAY. THE WAVE WATCH MODEL INDICATED THAT
SEAS COULD REACH 15 TO 20 FEET BY SUNDAY MORNING BEFORE SUBSIDING
SUNDAY AFTERNOON. WOULD LIKE TO SEE IF THIS TREND CONTINUES BEFORE
LATCHING ONTO THE MODEL SOLUTION. FOR NOW...HAVE CHOSEN TO SLIGHTLY
UNDERCUT GUIDANCE AND WENT WITH MARGINAL HIGH SURF CONDITIONS.

&&

.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 TONIGHT...THEN RISE AN ADDITIONAL THREE FEET ON
THURSDAY WITH A CREST JUST UNDER 9 FEET THURSDAY EVENING. THE RIVER
LEVEL WILL BEGIN FALLING THURSDAY NIGHT AND CONTINUE FALLING FRIDAY
AS HIGH PRESSURE MOVES OVER THE AREA.

AN ADDITIONAL RAINFALL FOR THE SLIDE AREA THROUGH THURSDAY NIGHT
WILL BE ON THE ORDER OF ABOUT ONE AND A HALF INCHES.

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

&&

.AVIATION...AN UPPER RIDGE OVER THE REGION WILL MOVE EAST THU
MORNING...ALLOWING AN UPPER TROF OFFSHORE TO APPROACH THE WA COAST.
STRONG WLY FLOW ALOFT WILL WEAKEN THU AFTERNOON. CONTINUED LOW LEVEL
ONSHORE OR SLY FLOW. EXPECT A COLD FRONT TO SWEEP ACROSS THE AREA
THU AFTERNOON.

CIGS ARE ANTICIPATED TO BE MAINLY IN THE 1-3K FT RANGE THRU
TONIGHT...ALTHOUGH EXPECT AREAS OF CIGS BLO 1K FT TO DEVELOP AFTER
0600 UTC. THERE WILL ALSO BE AREAS OF VSBYS IN THE 2-4SM RANGE DUE
TO RAIN AND/OR FOG. THE MTNS WILL REMAIN OBSCD.

KSEA...EXPECT CIGS TO BOUNCE BACK AND FORTH  BETWEEN MVFR AND VFR
CATEGORY THROUGH THIS EVENING. AFTER 0600 UTC...CIGS ARE EXPECTED TO
BE MAINLY IN THE 1-2K FT RANGE. ALSO...ANTICIPATE THE VSBY TO LOWER
TO 5 OR 6SM DUE TO -RA BR AFTER 0600 UTC. SLY WINDS NEAR 10 KT WILL
CONTINUE.

&&

.MARINE...ONSHORE OR SOUTHERLY FLOW WILL PREVAIL ACROSS THE AREA
THROUGH TONIGHT. A COLD FRONT WILL 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.
EXPECT A STRONG COLD OR OCCLUDED FRONT TO IMPACT THE AREA ON
SATURDAY. THERE IS A POSSIBILITY THAT WINDS COULD REACH GALE FORCE
OVER THE COASTAL WATERS AND STRAIT OF JUAN DE FUCA WITH THIS SYSTEM.

&&

.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 NEAR SHORE COASTAL WATERS...PUGET
      SOUND/HOOD CANAL...ADMIRALTY INLET...AND NORTHERN INLAND
      WATERS.

&&

$$

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