Blizzard and Heavy Snow in Alaska, December 8 to 10, 2008

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
107 PM AKST MON DEC 8 2008

.SHORT TERM...SIGNIFICANT SNOW AND WIND EVENT UNFOLDING FOR THE
SE PANHANDLE WITH A BLIZZARD WARNING MULTIPLE WINTER STORM
WARNINGS HIGH WIND WARNINGS AND WIND ADVISORIES. MADE LIMITED
CHANGES TO INHERITED GRIDS WITH THE ONLY CHANGES BASED ON THE
12Z GFS MODEL.

AN ARCTIC FRONT CONTINUES TO MOVE SOUTH THROUGH THE PANHANDLE AT
THIS TIME. THE ARCTIC FRONT IS EXPECTED TO CONTINUE TO MOVE SOUTH
AS THE GRADIENT CONTINUES TO INCREASE THROUGH THE DAY. THE FRONT
IS NOW EXPECTED TO MOVE FAR ENOUGH SOUTH AND WEST TO BRING ZONE 22
INTO THE COLD AIR. AS A RESULT A WINTER STORM WARNING HAS BEEN
ISSUED FOR ZONE 22 IN ADDITION TO THE WINTER STORM WARNINGS NOW IN
PLACE FOR 17 19 20 21 AND 25. SIGNIFICANT SNOWFALL IS EXPECTED
OVER THE NORTHERN ZONES WITH 18 TO 30 INCHES EXPECTED IN THE
HAINES ZONE AND 12 TO 20 INCHES EXPECTED IN THE JUNEAU ZONE.
BLIZZARD WARNING IS IN EFFECT FOR SKAGWAY AS STRONG WINDS ARE
EXPECTED ALONG WITH HEAVY SNOW.

961MB LOW CONTINUES TO MOVE NE TOWARDS THE NORTHER GULF OF ALASKA
WHILE A TRIPLE POINT LOW DEVELOPS AND MOVES OVER SOUTHERN BARANOF
ISLAND THIS EVENING. AMPLE MOISTURE FROM LOW LATITUDES IS BEING
ADVECTED NE INTO THE DEVELOPING STORM. SOUTHERN ZONES WILL BE WET
TONIGHT AND TOMORROW AS TEMPERATURES WILL REMAIN STEADY AND THEN
START TO WARM AS THE FRONT APPROACHES THE COAST.

.LONG TERM...OVERALL 12Z MODEL CONTINUITY AND AGREEMENT REMAINS
HIGH INTO EARLY NEXT WEEK AS A DRYING TREND WILL COMMENCE ACROSS
THE PANHANDLE BY FRIDAY MORNING. THE 12Z GFS 500 MB 5 WAVE PATTERN
INDICATES A BUILDING LONG WAVE RIDGE ACROSS THE WESTERN GULF
THURSDAY EVENING AND THIS WILL ALLOW FOR THE LOW AND MID LEVEL
FLOW ACROSS THE PANHANDLE TO TURN NORTHWESTERLY AND DRIER. THE 00Z
NAEFS ENSEMBLE ALSO AGREES WITH THE BUILDING LONG WAVE RIDGE
ACROSS THE CENTRAL GULF THROUGH THIS WEEKEND. WENT WITH A 12Z
GFS/ECMWF BLEND INTO THE CURRENT GRIDS THROUGH DAY 5 AS BOTH
MODELS WERE IN GOOD AGREEMENT THIS MORNING. THIS SOLUTION DIDNT
CHANGE MUCH IN THE INHERITED GRIDS...EXCEPT FOR BRINGING IN THE
DRIER AIR 12 HOURS LATER ACROSS THE SOUTHERN PANHANDLE FRIDAY. THE
12Z GFS IS BUILDING A STRONGER SURFACE HIGH, 1052 MB, BY 12Z
SUNDAY ACROSS THE YUKON THAN THE ECMWF, BUT WITH THE STRENGTH OF
THE MID LEVEL RIDGE BUILDING ACROSS THE CENTRAL GULF AND INTO THE
NORTHERN PANHANDLE THIS WEEKEND...THIS SOLUTION IS REALISTIC.

NEAR HANDOFF WITH SHORT TERM SURFACE RIDGING WILL BE BUILDING
NORTHWARD ACROSS THE PANHANDLE WITH WARMER SURFACE AIR. SO EXPECT
ALL RAIN ACROSS THE PANHANDLE WITH THE SNOW LEVEL RISING TO AROUND
1000 FEET NEAR SKAGWAY. THE 960 MB LOW EAST OF KODIAK TUESDAY
MORNING WILL BE FILLING AND WEAKENING AS IT MOVES NORTHWARD. THIS
STRONG LOW AND ASSOCIATED MID LEVEL TROUGH WILL INDUCE A LEE
TROUGH AND SURFACE LOW IN THE YUKON BY LATE TUESDAY INTO
WEDNESDAY. THE SOUTHERLY SURFACE PRESSURE GRADIENT INDUCED BY THE
STRENGTHENING LEE TROUGH WILL HELP WIND ADVY GUSTS TO COMMENCE OUT
OF THE SOUTHWEST NEAR SKAGWAY FROM TUESDAY EVENING THROUGH THE DAY
ON WEDNESDAY. ALSO WITH THE STRONG SOUTHERLY SURFACE PRESSURE
GRADIENT EXPECT SOUTHWESTERLY WIND GUSTS TO 35 KNOTS FROM CROSS
SOUND ACROSS THE EASTERN GULF TUESDAY NIGHT. ATTM MODELS ARE FLIP
FLOPPING ON THE STRENGTH A WEAK SURFACE LOW ADVECTING EASTWARD
ACROSS THE GULF WEDNESDAY EVENING AND THEN ACROSS THE PANHANDLE ON
THE DAY THURSDAY. BY WEDNESDAY EVENING THERE WILL AGAIN BE
SUFFICIENT COLD AIR ACROSS THE NORTHERN AND CENTRAL PANHANDLE FOR
SNOWFALL...BUT WITH THE SURFACE LOW PASSING ACROSS THE SOUTHERN
PANHANDLE EXPECTING SNOWFALL AMOUNTS TO BE LIGHT ATTM. IF THE
SURFACE LOW DOES ADVECT FURTHER NORTH WILL HAVE TO WATCH FOR MID
LEVEL DEFORMATION ZONE FORMATION AND HEAVIER SNOWFALL POTENTIAL.
AFTER THIS SURFACE LOW ADVECTS EASTWARD INTO BRITISH COLUMBIA
THURSDAY EVENING THE DRIER NORTHWESTERLY FLOW WILL BEGIN ACROSS
NORTHERN PANHANDLE AND MOVE SOUTHWARD THROUGH THE DAY ON FRIDAY.

FORECAST CONFIDENCE IS HIGH THROUGH SUNDAY WITH THE COMMENCING
DRYING TREND. EXPECT TEMPERATURES AND PRECIP BELOW NORMAL ACROSS
THE ENTIRE PANHANDLE FROM THURSDAY INTO EARLY NEXT WEEK WITH
TEMPERATURES POSSIBLY DROPPING TO NEAR 5 F ACROSS THE NORTHERN
PANHANDLE THIS WEEKEND WITH NORTHERLY WINDS. WILL HAVE TO WATCH
CROSS BARRIER FLOW LATE IN THE WEEKEND FOR POSSIBLE STRONG WINDS
OUT OF INTERIOR PASSES AND A TAKU WIND EVENT NEAR DOWNTOWN JUNEAU.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 9 PM THIS EVENING TO 3 AM AKST TUESDAY FOR
     AKZ024-026.
         HIGH WIND WARNING FROM 9 PM THIS EVENING TO 3 AM AKST TUESDAY
     FOR AKZ023-027-028.
         WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM AKST TUESDAY
     FOR AKZ017-019-020-025.
         WINTER STORM WARNING FROM 6 PM THIS EVENING TO 12 PM AKST
     TUESDAY FOR AKZ021-022.
         WIND ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR AKZ018.
         BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO 6 PM AKST TUESDAY FOR
     AKZ018.
         WIND ADVISORY UNTIL 3 AM AKST TUESDAY FOR AKZ017.
MARINE...STORM WARNING FOR PKZ036-041>043-051-052.
         GALE WARNING FOR PKZ011>013-021-022-031>035.

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CCC/PSS