Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 281058
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST SUN DEC 28 2014

.SYNOPSIS...AN UPPER TROUGH WILL BRING A CHANCE OF SHOWERS TODAY.
HIGH PRESSURE BUILDING OVER BRITISH COLUMBIA WILL PUSH MODIFIED
ARCTIC AIR SOUTH TONIGHT. A FEW SNOW SHOWERS ARE POSSIBLE TONIGHT AS
THE COLDER AIR MOVES IN. MOSTLY SUNNY AND COLD WEATHER WILL PREVAIL
AFTER THAT THROUGH THE MIDDLE OF NEXT WEEK WITH HIGH PRESSURE IN
CONTROL.

&&

.SHORT TERM...SCATTERED SHOWERS...MAINLY OVER THE MOUNTAINS AND IN A
PUGET SOUND CONVERGENCE ZONE NORTH OF SEATTLE...WILL CONTINUE TODAY
IN THE WAKE OF A COLD FRONT. WITH NORTHWEST FLOW ALOFT...THE
CONVERGENCE ZONE WILL PROBABLY SLOWLY SAG SOUTH INTO THE METRO AREA
THEN FALL APART. THE WINTER STORM WARNINGS AND ADVISORIES FOR THE
CASCADES WILL BE ALLOWED TO EXPIRE AT 6 AM THIS MORNING AS
PRECIPITATION RATES LET UP.

A MODIFIED ARCTIC FRONT WILL PUSH SOUTH INTO WESTERN WASHINGTON
TONIGHT AS STRONG HIGH PRESSURE MOVES INTO INTERIOR BRITISH
COLUMBIA. THE LOW LEVELS WILL BECOME COLD ENOUGH FOR PRECIPITATION
TO CHANGE OVER TO SNOW TONIGHT FOR MOST OF THE LOWLANDS. AT THIS
POINT...PRECIPITATION TONIGHT IS FORECAST TO BE SPOTTY AND SHOWERY
AND SNOW ACCUMULATIONS...IF ANY...ARE NOT EXPECTED TO BE SIGNIFICANT.

DRIER AIR FROM THE NORTH WILL BRING AN END TO ANY SHOWERS OVER THE
AREA ON MONDAY. FRASER OUTFLOW WILL PEAK AND WIND ADVISORY NORTHEAST
WINDS ARE LIKELY FOR THE NORTHWEST INTERIOR. HIGHS WILL STRUGGLE TO
REACH 40 MONDAY AND LOWS WILL FALL INTO THE 20S MONDAY NIGHT UNDER
MOSTLY CLEAR SKIES WITH TEENS POSSIBLE IN A FEW COLDER SPOTS.
TUESDAY WILL BE ANOTHER COLD AND MOSTLY SUNNY DAY WITH HIGHS MOSTLY
IN THE MID TO UPPER 30S AND ANOTHER COLD NIGHT TUESDAY NIGHT.
SCHNEIDER

.LONG TERM...AN UPPER RIDGE WILL BE OVER THE AREA ON WEDNESDAY FOR A
DRY BUT COOL DAY. THE RIDGE WILL BEGIN TO WEAKEN ON THURSDAY AS
SHORT WAVE ENERGY COMES OVER THE TOP BUT IT LOOKS LIKE ANOTHER DRY
DAY...PROBABLY WITH A FEW MORE CLOUDS. TEMPERATURES SHOULD ALSO
BEGIN TO MODERATE ON THURSDAY. A WEATHER SYSTEM IN THE NORTHWEST
FLOW ALOFT WILL SAG SOUTH OVER THE AREA ON FRIDAY FOR A CHANCE OF
RAIN. SNOW LEVELS WILL STILL BE LOW AND IT IS NOT OUT OF THE
QUESTION THAT THERE COULD BE SOME LOWLAND SNOW...ESPECIALLY OVER THE
NORTH INTERIOR. SCHNEIDER

&&

.HYDROLOGY...FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS.

&&

.AVIATION...NORTHWEST FLOW ALOFT OVER THE PACIFIC NORTHWEST EARLY
THIS MORNING WILL VEER TO NORTHERLY TONIGHT AS AN UPPER LEVEL RIDGE
BUILDS INTO BRITISH COLUMBIA. AT THE SURFACE...NORTHERLY OFFSHORE
FLOW WILL DEVELOP TODAY AND INCREASE TONIGHT AS A STRONG HIGH MOVES
SOUTH THROUGH BRITISH COLUMBIA. THE AIR MASS WILL REMAIN STABLE AND
MOIST...WITH MOISTURE BECOME LIMITED TO LOWER LEVELS LATE TONIGHT.

THE PUGET SOUND CONVERGENCE ZONE...WHICH EXTENDED FROM SOUTHERN
WHIDBEY ISLAND TO AROUND STEVENS PASS AT 2 AM...WILL REMAIN NORTH OF
SEATTLE AS IT WEAKENS AND DISSIPATES THIS MORNING.

LOCALLY SUSTAINED NORTHEAST WINDS OF 25 KT WILL DEVELOP LATE TONIGHT
IN THE NORTH INTERIOR...ESPECIALLY NEAR THE MOUTH OF THE FRASER
RIVER.

SHOWERS AND MVFR CONDITIONS CONTINUE IN THE CONVERGENCE ZONE...WITH
SCATTERED SHOWERS ELSEWHERE MAINLY ALONG THE COAST AND WEST SLOPES
OF THE MOUNTAINS. THE CASCADES WILL REMAIN GENERALLY OBSCURED
THROUGH THIS EVENING.

KSEA...SOUTH WIND 4-8 KT...BECOMING NORTHEAST 6-12 KT LATE TODAY AND
TONIGHT. COLDER AIR WILL MOVE INTO THE PUGET SOUND REGION LATE
TONIGHT AS SHOWERS ARE GENERALLY ENDING. SNOW IS UNLIKELY AT KSEA
BUT CANNOT BE RULED OUT ENTIRELY.   MCDONNAL

&&

.MARINE...STRONG HIGH PRESSURE WILL BEGIN MOVING SOUTH THROUGH
BRITISH COLUMBIA TODAY...WHILE A WEAK LOW TRACKS SOUTH ALONG THE
PACIFIC NORTHWEST COAST. AS A RESULT NORTHERLY OFFSHORE FLOW WILL
DEVELOP...THEN INCREASE TONIGHT AND MONDAY...PROBABLY REACHING ITS
PEAK LATE MONDAY OR MONDAY EVENING. A GALE WATCH IS IN EFFECT FOR
THE NORTHERN INLAND WATERS...THE CENTRAL AND WESTERN STRAIT OF JUAN
DE FUCA...AND THE NORTHERN COASTAL WATERS. SMALL CRAFT ADVISORY
WINDS ARE LIKELY ALL OTHER ZONES.

NORTHWEST SWELL OF 12 TO 15 FT THIS MORNING WILL SUBSIDE LATE TODAY
AND TONIGHT.

OFFSHORE FLOW WILL WEAKEN TUESDAY...WITH WINDS OF 20 KT OR LESS
WEDNESDAY AND THURSDAY.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WINTER STORM WARNING CASCADES FROM SNOHOMISH COUNTY THROUGH
     LEWIS COUNTY THROUGH 6 AM.
     WINTER WEATHER ADVISORY WHATCOM-SKAGIT CASCADES THROUGH 6 AM.

PZ...SMALL CRAFT ADVISORY COASTAL WATERS THROUGH TONIGHT.
     SMALL CRAFT ADVISORY WEST ENTRANCE STRAIT TODAY FOR HAZARDOUS
       SEAS.
     SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR
       THROUGH THIS EVENING.
     GALE WATCH NORTHERN INLAND WATERS...CENTRAL AND WESTERN STRAIT
       OF JUAN DE FUCA...NORTHERN COASTAL WATERS.

&&

$$

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








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