Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 261624
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PDT SUN OCT 26 2014

.SYNOPSIS...A COOL UPPER LEVEL TROUGH WILL MOVE THROUGH WESTERN
WASHINGTON TODAY...BRING SHOWERS TO THE LOWLANDS AND SNOW TO HIGHER
ELEVATIONS IN THE MOUNTAINS. A WET WEATHER SYSTEM WILL ARRIVE MONDAY
NIGHT AND TUESDAY. THIS SYSTEM COULD BRING SIGNIFICANT RAIN TO
THE AREA WITH THE REMAINS OF HURRICANE ANA EMBEDDED IN THE SYSTEM.
ADDITIONAL WEATHER SYSTEMS WILL ARRIVE LATER IN THE WEEK.

&&

.SHORT TERM...RADAR SHOWS SCATTERED SHOWERS OVER MOST OF THE AREA
AND A MORE ORGANIZED SHOWER BAND MOVING ONTO THE COAST. SHOWERS WILL
BE MOST LIKELY IN THE MOUNTAINS TODAY AND WITH THE COOL AIR MASS IN
PLACE A LOT OF THIS PRECIPITATION WILL BE SNOW. HAVE ISSUED A WINTER
STORM WARNING FOR THE MOUNTAINS ABOVE 3500 FEET TODAY. AS THIS IS
THE FIRST EVENT OF THE SEASON THE CRITERIA FOR A WINTER STORM ARE
LOWER...JUST 4 INCHES. WEBCAMS THIS MORNING SHOW AROUND THAT MUCH AT
PARADISE AND WHITE PASS...WITH SNOQUALMIE AND STEVENS PASSES SHOWING
RAIN ON THE ROADWAYS.

MONDAY WILL BE MOSTLY DRY WITH RAIN DEVELOPING ON THE COAST IN THE
AFTERNOON. THE NEXT SYSTEM WILL MOVE THROUGH WESTERN WASHINGTON
MONDAY NIGHT AND TUESDAY. MODELS SHOW IT HAS SOME TROPICAL MOISTURE
FROM FORMER HURRICANE ANA SO RAINFALL AMOUNTS COULD BE HEAVY...
ESPECIALLY ON THE COAST AND OLYMPICS. IT WILL PROBABLY BE WINDY ON
THE COAST AND OVER THE NORTH INTERIOR AS THIS SYSTEM MOVES INLAND.
TEMPERATURES OVER THE NEXT THREE DAYS WILL BE NEAR SEASONAL NORMS
WITH HIGHS IN THE MID AND UPPER 50S AND LOWS IN THE 40S. BURKE

.LONG TERM...PREVIOUS DISCUSSION...EXTENDED MODELS IN FAIRLY GOOD
AGREEMENT THIS MORNING. SHOWERS DECREASING ON WEDNESDAY WITH A WEAK
RIDGE OF HIGH PRESSURE BUILDING OVER THE AREA. THE GFS IS A LITTLE
STRONGER WITH THE RIDGE LEADING TO LESS SHOWER ACTIVITY VERSUS THE
ECMWF BUT EVEN WITH THE DRIER GFS SOLUTION WILL HAVE TO KEEP CHANCE
POPS IN THE FORECAST. BOTH THE GFS AND ECMWF SHOW A DEEP TROUGH
DEVELOPING OFF THE WEST COAST FOR THURSDAY AND FRIDAY WITH MOIST
SOUTHWESTERLY FLOW ALOFT OVER WESTERN WASHINGTON. THE TROUGH
OFFSHORE WILL BE DIGGING SOUTH WITH BRINGS UP THE CHANCE THAT ONE OF
THE SYSTEMS SPINNING OUT OF THE TROUGH COULD GET STALLED OVER
WESTERN WASHINGTON. TIMING THESE FEATURES AT THIS POINT WOULD BE
TOUGH BUT THE 00Z RUN SOLUTIONS INDICATE AT LEAST LIKELY POPS ARE
WARRANTED FOR THURSDAY AND FRIDAY AND HAVE GONE AHEAD AND MADE THESE
CHANGES. UPPER LEVEL TROUGH MOVING INLAND FRIDAY NIGHT AND SATURDAY
FOR A CHANCE OF SHOWERS AT THAT TIME. FELTON

&&

.HYDROLOGY...A BREAK IN THE RAIN TODAY THROUGH MONDAY WILL ALLOW THE
SKOKOMISH RIVER TO RECEDE. WILL HAVE TO KEEP AN EYE ON THE RIVER
TUESDAY WITH UP TO ANOTHER THREE INCHES OF RAIN EXPECTED ALONG THE
SOUTH SLOPES OF THE OLYMPICS MONDAY NIGHT. THERE IS A POSSIBILITY
THAT THE SKOKOMISH COULD FLOOD AGAIN TUESDAY.

ON ALL OTHER RIVERS FLOODING IS UNLIKELY OVER THE NEXT 7 DAYS. BURKE

&&

.AVIATION...AN UPPER LEVEL TROUGH OVER WESTERN WASHINGTON THIS
MORNING WILL MOVE EAST OF THE CASCADES THIS AFTERNOON...AND A WEAK
UPPER RIDGE WILL MOVE INTO THE REGION TONIGHT. NORTHWEST FLOW ALOFT
WILL PREVAIL. THE AIR MASS WILL BE MOIST AND WEAKLY UNSTABLE
TODAY...THEN GRADUALLY DRY AND STABILIZE TONIGHT. STRONG ONSHORE
FLOW THIS MORNING WILL EASE AND TURN WEAKLY OFFSHORE TONIGHT.

MAINLY VFR CONDITIONS WILL PREVAIL TODAY AND TONIGHT WITH SKY COVER
ROUGHLY SCT-BKN040 BKN080 BKN110. HOWEVER SHOWERS WILL CONTINUE...
PRODUCING LOCAL MVFR CONDITIONS. GUSTY WINDS...MAINLY IN THE PUGET
SOUND REGION...WILL GRADUALLY EASE THIS AFTERNOON.

KSEA...SOUTHWEST WIND 10-16 KT GUSTING 22 KT...EASING TO 8-14 KT
AROUND 3 PM.   MCDONNAL

&&

.MARINE...ONSHORE FLOW WILL EASE TODAY AS A SURFACE RIDGE OVER THE
OFFSHORE WATERS SHIFTS INTO WESTERN WASHINGTON. THE RIDGE WILL MOVE
EAST OF THE CASCADES TONIGHT AND MONDAY. SMALL CRAFT ADVISORY WINDS
WILL CONTINUE INTO THIS AFTERNOON OVER THE PUGET SOUND AND HOOD
CANAL...AND INTO THIS EVENING OVER THE CENTRAL STRAIT OF JUAN DE
FUCA AND EAST ENTRANCE STRAIT.

ANOTHER VIGOROUS FRONTAL SYSTEM WILL AFFECT THE COASTAL AND INLAND
WATERS OF WESTERN WASHINGTON LATE MONDAY THROUGH TUESDAY. ITS WARM
FRONT WILL PRODUCE SOUTHERLY GALES IN THE COASTAL WATERS PROBABLY
BEGINNING LATE MONDAY...AND AT THE ENTRANCES TO THE STRAIT AND
NORTHERN INLAND WATERS MONDAY EVENING. THE COLD FRONT WILL MOVE
THROUGH THE FORECAST AREA LATE MONDAY NIGHT AND TUESDAY MORNING.

A SURFACE TROUGH WILL BE OVER THE AREA TUESDAY...GIVING WAY TO WEAK
HIGH PRESSURE ON WEDNESDAY. ANOTHER PACIFIC FRONTAL SYSTEM WILL
APPROACH THE AREA ON THURSDAY.   MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WINTER STORM WARNING TODAY CASCADES AND OLYMPICS.
PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT ADMIRALTY
      INLET...NORTHERN INLAND WATERS.
      SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR.

&&

$$

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





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