Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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067
FXUS66 KSEW 021133
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PST TUE FEB 2 2016

.SYNOPSIS...A WEAK FRONT OFFSHORE TODAY WILL DISSIPATE AS IT MOVES
INLAND TONIGHT. ANOTHER STRONGER FRONT WILL THROUGH WESTERN
WASHINGTON WEDNESDAY AND WEDNESDAY NIGHT BRINGING RAIN AND MOUNTAIN
SNOW. LIGHT RAIN PRODUCED BY A WARM FRONT WILL REACH THE AREA
THURSDAY. THE ASSOCIATED STRONG COLD FRONT WILL BRING ANOTHER ROUND
OF RAIN AND MOUNTAIN SNOW TO THE AREA FRIDAY. DRIER WEATHER MAY
DEVELOP LATER IN THE WEEKEND AS HIGH PRESSURE BUILDS OVER THE REGION.

&&

.SHORT TERM...THE LONG WAVE TROUGH PATTERN HAS SHIFTED EWD BUT THE
PAC NW REMAINS ON THE BACK SIDE UNDER NW FLOW ALOFT. A WEAK
EMBEDDED SHORT WAVE WITH A NEGATIVE TILT SURFACE FRONT IS SPREADING
MAINLY MID AND HIGH LEVEL CLOUDS INTO PARTS OF WRN WA THIS MORNING.
THIS WILL HELP INHIBIT WIDESPREAD FOG...BUT PATCHY FOG FORMATION IS
STILL LIKELY AROUND THE MORE PRONE LOCATIONS LIKE THE SW
INTERIOR/FAR S PUGET SOUND. MODELS INDICATE THAT THE NEXT SYSTEM OUT
NEAR 150 W WILL HELP KICK THE DISSIPATING FRONT OFFSHORE INTO WRN WA
TONIGHT WITH JUST A CHANCE OF RAIN...EXCEPT LIKELY W OF PUGET SOUND
TOWARD THE COAST. QPF AMOUNTS WILL BE QUITE LIGHT AND SPOTTY WITH
LITTLE OR NO SNOW ACCUMULATION IN THE MOUNTAINS.

MODELS INDICATE THE NEXT STRONGER FRONT WITH SIGNIFICANTLY MORE
MOISTURE WILL SPREAD RAIN INTO WRN WA WEDNESDAY. THIS WILL BE A
PROGRESSIVE SYSTEM WITH THE SURFACE FRONT SWEEPING ACROSS INTERIOR
WRN WA BY WEDNESDAY EVENING. A QUARTER TO A HALF INCH OF RAIN IS
LIKELY BEFORE THE TRANSITION OVER TO SHOWERS WEDNESDAY NIGHT.
PRECIPITATION WILL FALL AS SNOW IN THE MOUNTAINS...INCLUDING THE
PASSES WITH A SNOW LEVEL RANGING FROM 2000 TO 2500 FEET. THE WRF-GFS
PRODUCES ABOUT 4 TO 8 INCHES OF SNOW...AND LOCALLY NEAR A FOOT ON
THE VOLCANOS BY THURSDAY MORNING. AN ADVISORY WILL PROBABLY BE
NEEDED FOR THIS SYSTEM BUT AMOUNTS LOOK SHORT OF WARNING CRITERIA AT
THIS POINT.

HIGHER PRESSURE ALOFT TRIES TO BUILD OVER THE AREA THURSDAY
AFTERNOON WITH SHOWERS DECREASING. SOME MODELS LIFT A WARM FRONTAL
WAVE OVER THE RIDGE THURSDAY AFTERNOON...BRUSHING WRN WA WITH SOME
RAIN. WILL MAINTAIN CHANCE POPS IN THE FORECAST FOR NOW. IT WILL BE
A BIT MILDER AS THIS WARM FRONT MOVES BY WITH HIGHS POSSIBLY IN THE
LOW 50S IN SPOTS.

.LONG TERM...ANOTHER STRONG FRONT WILL AFFECT THE PAC NW FRIDAY AND
FRIDAY NIGHT. TIMING IS A BIT UNCERTAIN BUT THE FRONT LOOKS WET AND
SHOULD SPREAD RAIN INTO WRN WA FRIDAY OR FRIDAY EVENING AT THE LATEST.
AGAIN...THIS WILL BE ANOTHER PROGRESSIVE SYSTEM SO THE HEAVY RAIN/MOUNTAIN
SNOW WITH THE FRONT SHOULD NOT BE TOO PROLONGED. THIS WILL HELP MINIMIZE
THE FLOOD THREAT. SEE THE HYDRO DISCUSSION FOR DETAILS.

MODELS HAVE TRENDED TOWARD A STRONGER RIDGE FOR THE WEEKEND. 00Z/06Z
RUNS OF THE GFS AND ECMWF ARE FASTER TO DEVELOP DRY CONDITIONS
SATURDAY. PREVIOUS MODEL SOLUTIONS HELD RAIN BACK OVER PAC NW
SATURDAY SO THE EXTENDED RUNS REMAIN UNSTABLE. WILL LEAVE THE
EXTENDED FORECAST ALONE FOR NOW AND LET THE NEXT SHIFT EVALUATE ALL
THE 12Z RUNS BEFORE MAKING ANY CHANGES. SUNDAY STILL LOOKS DRY AND
IF THE TRENDS HOLD...IT COULD BE A RATHER PLEASANT AND MOSTLY DRY
WEEKEND. MERCER

&&

.AVIATION...DISSIPATING FRONT OVER THE COASTAL WATERS TODAY AND
TONIGHT. NORTHWESTERLY FLOW ALOFT. AIR MASS STABLE WITH MAINLY MID AND HIGH
LEVEL MOISTURE.

KSEA...SCATTERED LAYER AROUND 5000 FEET WITH HIGH CLOUDS ABOVE. 5000
FOOT LAYER COULD GO BROKEN FOR A COUPLE HOURS THIS MORNING.
INCREASING MID LEVEL CLOUDS TONIGHT. LIGHT EAST TO SOUTHEAST WINDS
BECOMING LATE AFTERNOON. FELTON

&&

.MARINE...FRONT DISSIPATING OVER THE COASTAL WATERS TODAY AND
TONIGHT. A MUCH STRONGER FRONT WILL MOVE INTO THE COASTAL WATERS ON
WED AND PUSH INLAND WED AFTERNOON. SMALL CRAFT ADVISORY CONDITIONS
AHEAD OF THE FRONT FOR THE COASTAL WATERS MOST OF THE INLAND WATERS.
GALE FORCE WINDS ARE POSSIBLE WITH THE FRONT WEDNESDAY AFTERNOON OVER
THE COASTAL WATERS AS WELL AS THE CENTRAL AND EASTERN STRAIT OF JUAN
DE FUCA.

HIGH PRESSURE WILL BUILD OVER THE AREA ON THURSDAY. ANOTHER VIGOROUS
FRONT WILL MOVE THROUGH THE AREA ON FRIDAY. GALE FORCE WINDS ARE
POSSIBLE AGAIN WITH THIS SYSTEM OVER THE COASTAL WATERS. ANOTHER
RIDGE OF HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT ON SATURDAY.
FELTON

&&

.HYDROLOGY...STRONG FRONTS ON WEDNESDAY AND AGAIN ON FRIDAY WILL BRING
A PERIOD OF HEAVY RAIN. HOWEVER...MODELS INDICATE THIS SYSTEMS WILL MOVE
RAPIDLY ACROSS THE AREA WHICH SHOULD LIMIT ANY FLOOD POTENTIAL. THE SKOKOMISH
RIVER IS THE ONLY RIVER THAT REALLY BARES WATCHING BUT FLOODING DOES NOT
APPEAR LIKELY AT THIS TIME. OTHERWISE...FLOODING IS NOT EXPECTED OVER THE
NEXT 7 DAYS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS...EAST ENTRANCE TO THE STRAIT.
     GALE WATCH COASTAL WATERS...CENTRAL STRAIT AND EAST ENTRANCE
     WEDNESDAY AFTERNOON.

&&

$$

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