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150
FXUS66 KSEW 170416
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 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 RAIN CHANGING TO SHOWERS LATE THURSDAY. THE HIGHER
ELEVATIONS OF THE MOUNTAINS WILL GET SNOW BUT THE SNOW LEVEL WILL BE
A LITTLE TOO HIGH FOR MUCH ACCUMULATION IN THE PASSES. IT WILL BE
BREEZY THURSDAY EVENING BEHIND THE FRONT IN STRONG ONSHORE FLOW.
SHOWERS WILL TAPER OFF THURSDAY NIGHT EXCEPT IN THE PUGET SOUND
CONVERGENCE ZONE AND THE MTNS. FRIDAY LOOKS DRY PERIOD WITH WEAK
HIGH PRESSURE OVER THE AREA. A FRONT WILL BRING RAIN TO THE COAST
AROUND MIDDAY SATURDAY SPREADING INLAND IN THE AFTERNOON.

.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.

&&

.AVIATION...SOUTHWESTERLY FLOW ALOFT OVER WESTERN WASHINGTON WITH
WARM FRONT OVER THE AREA INTO THURSDAY MORNING. TRAILING COLD FRONT
REACHING THE COAST THURSDAY AFTERNOON MOVING THROUGH THE INTERIOR
LATE THURSDAY AFTERNOON.

SCATTERED TO BROKEN LAYER NEAR 1500 FEET WITH OVERCAST LAYER
3000-4000 FEET. LOCAL CEILINGS BELOW 1000 FEET AND VISIBILITIES 2 TO
4 SM IN LIGHT RAIN AND FOG. MOUNTAINS REMAINING OBSCURED.

KSEA...A LITTLE BREAK IN THE RAIN LATE THIS EVENING WITH CEILINGS
NEAR 3000 FEET. CEILINGS LOWERING DOWN TO 1000-2000 FEET OVERNIGHT
WITH VISIBILITIES 3-5 SM AT TIMES WITH THE RAIN PICKING UP AGAIN.
LITTLE CHANGE IN THE CONDITIONS THURSDAY MORNING INTO THURSDAY
AFTERNOON. SOUTHERLY WINDS 6 TO 10 KNOTS. FELTON

&&

.MARINE...ONSHORE OR SOUTHERLY FLOW WILL PREVAIL ACROSS THE AREA
TONIGHT. A COLD FRONT WILL MOVE ACROSS THE REGION ON THU WITH SMALL
CRAFT ADVISORY WINDS OVER THE COASTAL WATERS AS WELL AS ADMIRALTY
INLET...EAST ENTRANCE TO THE STRAIT AND THE NORTHERN INLAND WATERS.
SMALL CRAFT WESTERLY WINDS EXPECTED BEHIND THE FRONT IN THE STRAIT
THURSDAY NIGHT. 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.
FELTON
&&

.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 ADVISORIES ARE IN EFFECT FOR THE COASTAL WATERS...
     ADMIRALTY INLET...EAST ENTRANCE OT THE STRAIT AND NORTHERN
     INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML










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