Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 250418
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
920 PM PDT FRI OCT 24 2014

.SYNOPSIS...RAIN WILL SPREAD FROM SOUTH TO NORTH TONIGHT. A FILLING
LOW PRESSURE CENTER WILL MOVE ACROSS THE AREA SATURDAY NIGHT...
BRINGING RAIN AND LOCALLY WINDY CONDITIONS. SUNDAY AND MONDAY WILL
BE SHOWERY. WET AND BREEZY WEATHER ARE LIKELY AT TIMES NEXT WEEK.

&&

.SHORT TERM...A WARM FRONT WILL LIFT NORTH THROUGH THE REGION
TONIGHT. RAIN HAS ALREADY SPREAD AS FAR NORTH AS NORTHERN PUGET
SOUND AND SHOULD FILL IN OVER THE REMAINDER OF THE NORTHWEST
INTERIOR IN THE NEXT FEW HOURS. MESO MODELS SHOW A FAIRLY DISTINCT
BACK EDGE TO THE RAINS LATER TONIGHT AND IT LOOKS LIKE THE SOUTH
INTERIOR WILL SEE RAIN ENDING SOMETIME IN THE EARLY MORNING HOURS OR
EVEN LATE THIS EVENING. THERE SHOULD ALSO BE SOME GUSTY EAST WINDS
OVER THE EAST PUGET SOUND LOWLANDS THROUGH SATURDAY MORNING WITH
INCREASING EASTERLY GRADIENTS AHEAD OF THE FRONTAL SYSTEM.

A COLD FRONT WILL MOVE ONSHORE ON SATURDAY. AREAS WHERE RAIN TAPERS
LATER TONIGHT OR EARLY SATURDAY MORNING SHOULD SEE RAIN REDEVELOP
DURING THE DAY. THE CURRENT CHANCE OF RAIN FORECAST FOR PARTS OF THE
INTERIOR ON SATURDAY MIGHT BE TOO OPTIMISTIC.

A FILLING SURFACE LOW WILL MOVE ONSHORE NEAR THE CENTRAL WASHINGTON
COAST IN THE AFTERNOON AND TRACK NORTHEAST ACROSS WESTERN WASHINGTON
DURING THE EVENING. BREEZY TO WINDY SOUTH TO WEST WINDS ARE LIKELY
BEHIND THE LOW IN THE EVENING. THIS LOOKS LIKE A BLUSTERY PATTERN
FOR THE SEATTLE AREA.

SHOWERS WILL LINGER INTO SUNDAY BEHIND THE FRONT BUT THE TREND
SHOULD BE FOR DECREASING PRECIPITATION AS WEAK HIGH PRESSURE ALOFT
BUILDS IN. IT LOOKS FAIRLY DRY MOST AREAS BY SUNDAY NIGHT BUT
PRECIPITATION CHANCES WILL BE INCREASING AGAIN ON MONDAY AS ANOTHER
FRONTAL SYSTEM APPROACHES FROM THE WEST. SCHNEIDER

.LONG TERM...PREVIOUS DISCUSSION...MODELS AGREE THE NEXT SYSTEM WILL
BE NEARING THE COAST MONDAY NIGHT. THERE IS A DEEP LOW ASSOCIATED
WITH THIS SYSTEM THAT IS FORECAST TO CROSS NORTHERN VANCOUVER ISLAND
TUESDAY. SOUTHEAST GRADIENTS WILL BE STRONG ACROSS WESTERN
WASHINGTON BUT WITH THIS PATTERN THERE IS USUALLY NO HIGH WIND.
AFTER RAIN TUESDAY...SHOWERS FOLLOW ON WEDNESDAY AND THURSDAY.
ANOTHER SYSTEM MAY ARRIVE AROUND NEXT FRIDAY. TEMPERATURES NEXT WEEK
WILL BE NEAR SEASONAL NORMS WITH HIGHS IN THE 50S AND LOWS IN THE
40S. BURKE

&&

.HYDROLOGY...THE SKOKOMISH RIVER WILL RISE AGAIN IN RESPONSE TO
HEAVY RAIN TONIGHT AND SATURDAY. SINCE IT IS STILL RUNNING HIGH FROM
THE PREVIOUS EVENT...IT IS POSSIBLE THE RIVER WILL GET CLOSE TO
FLOOD STAGE ON SATURDAY. FOR NOW THE FORECAST TAKES THE STAGE AT
POTLATCH TO BETWEEN 15.5 AND 16 FEET. FLOOD STAGE IS 16.5 FEET. ON
OTHER RIVERS FLOODING IS UNLIKELY OVER THE NEXT 7 DAYS.

&&

.AVIATION...MOIST SOUTHWEST FLOW ALOFT WILL CONTINUE OVER W WA AS A
WARM FRONT MOVES N ACROSS W WA THROUGH 12Z. CIGS ARE EXPECTED TO
LOWER TO MVFR LEVELS...WITH SPOTTY IFR CONDITIONS...AS THE RAIN
MOISTENS THE LOWER AIR MASS. A COLD FRONT WILL MOVE INLAND ACROSS W
WA SATURDAY MORNING. THE MAIN UPPER LEVEL AND SURFACE LOW WILL
FOLLOW SATURDAY AFTERNOON AND NIGHT. MVFR CIGS ARE EXPECTED TO
PREDOMINATE THROUGH SATURDAY NIGHT.

KSEA...WARM FRONT RAIN HAS REACHED KSEA AND CIGS WILL GRADUALLY
LOWER AS THE RAIN MOISTENS THE LOWER AIR MASS. CIGS WILL REMAIN VFR
THROUGH 07Z AND SHOULD LOWER TO MVFR LEVELS AFTER 12Z. CONDITIONS
WILL LIKELY DETERIORATE TO LOW-END MVFR AND PERHAPS OCCASIONAL IFR
IN RAIN AND FOG SATURDAY MORNING. SURFACE WINDS WILL BE N-NE 4-10KT
THROUGH 12Z. A SHIFT TO S WINDS WILL PROBABLY OCCUR AROUND 15Z OR
SO. KAM

&&

.MARINE...A WARM FRONT WILL MOVE NORTH ACROSS THE AREA TONIGHT. THE
VARIOUS MODELS HAVE NOT BEEN IN COMPLETE AGREEMENT WITH THE
EVOLUTION OF THIS SYSTEM INCLUDING THE STRUCTURE AND TRACK OF THE
SURFACE LOW OR LOWS. THEY HAVE LEANED TOWARD A SOLUTION THAT MOST OF
THE MESOSCALE MODELS HAVE AND WHICH IS SIMILAR TO 12Z ECMWF. THIS
BRINGS ABOUT A 994 MB SURFACE LOW NE ACROSS THE COASTAL WATERS ON
SATURDAY. THIS LOW IS ASSOCIATED WITH THE TRAILING COLD FRONT. NEW
00Z NAM AND HRRR INDICATE AREAS OF GALE FORCE WINDS SPREADING N
ACROSS THE SOUTHERN FOUR COASTAL ZONES LATE TONIGHT...THEN
CONTINUING OFF AND ON THROUGH EARLY SATURDAY AFTERNOON. THE 00Z NAM
AND 12Z ECMWF THEN BRING A SECOND SURFACE LOW ASSOCIATED WITH MAIN
UPPER LEVEL LOW NE ACROSS ASTORIA AROUND 00Z SUNDAY/5 PM SATURDAY
THEN CONTINUING N-NE TOWARD EITHER N CENTRAL WA OR THE N INTERIOR
EARLY SATURDAY EVENING. THIS TRACK HAS THE POTENTIAL FOR SCA OR
BETTER WINDS OVER THE INTERIOR WATERS. CONFIDENCE IS LOW HERE BASED
ON THE UNCERTAIN TRACK OF THE SECOND LOW.

HIGH PRESSURE WILL BUILD OVER THE REGION SUNDAY AND BEGIN TO MOVE
EAST OF THE AREA MONDAY. ANOTHER VIGOROUS FRONTAL SYSTEM WILL AFFECT
THE AREA MONDAY NIGHT AND TUESDAY.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY FOR THE EAST PUGET SOUND LOWLANDS TONIGHT THROUGH
     SATURDAY MORNING.
     WIND ADVISORY FOR BELLEVUE AND VICINITY TONIGHT.
PZ...GALE WARNING SOUTHERN FOUR COASTAL ZONES.
     SMALL CRAFT ADVISORY NORTHERN TWO COASTAL ZONES AND WEST
      ENTRANCE OF THE STRAIT.

&&

$$

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








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