Blizzard and Heavy Snow in Alaska, December 2 to 4, 2010

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST THU DEC 2 2010

.MODEL DISCUSSION...MODELS INITIALIZED WELL ON THE STORM CENTER OVER
THE BERING SEA. MODEL FORECASTS ARE IN GENERALLY GOOD AGREEMENT. WILL
BE LEANING TOWARD THE HIGHER RESOLUTION NAM...ESPECIALLY OVER
SOUTHCENTRAL ALASKA ON THIS FORECAST PACKAGE.

.SHORT TERM FORECAST...
THE MAJOR WEATHER FEATURES AFFECTING THE FORECAST AREA ARE THE STORM
FORCE LOW CENTER OVER THE BERING SEA AND ITS ASSOCIATED FRONTAL
SYSTEM WHICH MARCHES ACROSS SW ALASKA LATE TONIGHT AND INTO
SOUTHCENTRAL ALASKA FRIDAY.

UPPER LEVELS...A WEAK TROUGH OVER THE DELTA THIS MORNING WEAKENS AS
ITS MOVES ACROSS THE MAINLAND TODAY. A LARGE LOW CENTER OVER THE
CENTRAL BERING SEA SLOWLY WEAKENS AS IT MOVES TO OVER BRISTOL BAY SAT
AFTERNOON. A STRONG SOUTHWESTERLY JET OVER ALEUTIANS AND EASTERN
BERING SEA MOVES TO OVER THE AK PEN AND SW ALASKA LATE TONIGHT. ON
FRI...THE BROAD SOUTHWESTERLY JET EXTENDS FROM SOUTH OF THE ALEUTIANS
TO OVER THE GULF OF ALASKA AND SOUTHCENTRAL ALASKA. THIS FEATURE THEN
MOVES EAST TO OVER THE SOUTHERN GULF AND SE ALASKA SAT AFTERNOON. AS
THE RIDGE BUILDS TO THE WEST A STRONG NORTHERLY JET DEVELOPS OVER THE
WEST ALEUTIANS/BERING SEA FRI...THEN MOVES TO THE EASTERN
ALEUTIANS/BERING SEA SAT.

.SURFACE...
A WEAK FRONTAL TROUGH TIED TO A WEAK UPPER TROUGH MOVES EAST ACROSS
THE MAINLAND TONIGHT. A STACKED 970S OVER THE CENTRAL BERING SEA
WEAKENS AS IT MOVES TO NEAR NUNIVAK ISLAND FRI AFTERNOON. THIS LOW
EVENTUALLY ENDS UP SOUTH OF KODIAK WITH A PRESSURE IN THE LOWER 990S
LATER SAT. THE ASSOCIATED FRONT MOVES TO OVER THE DELTA AND WESTERN
BRISTOL BAY THIS EVENING AND INTO SOUTHCENTRAL ALASKA FRI. A TRIPLE
POINT LOW IS EXPECTED TO DEVELOP NEAR KODIAK ISLAND LATE FRI MORNING.
THIS CENTER WILL WEAKEN AS IT MOVES OVER THE WESTERN KENAI PENINSULA
FRI NIGHT. THE FRONT MOVES TO THE EASTERN GULF OF ALASKA SAT.

.SOUTHCENTRAL ALASKA...
SOUTHCENTRAL WILL TRANSITION FROM GENERALLY DRY AND COLD TO VERY
WINDY AND WET STARTING FRI AND CONTINUING INTO EARLY SAT. THE STRONG
WEATHER FRONT WHICH MOVES TO THE WESTERN GULF AND ACCOMPANYING LOW
WHICH DEVELOPS NEAR KODIAK ISLAND FRI WILL PRODUCE VERY STRONG
PRESSURE GRADIENTS ACROSS SOUTHCENTRAL ALASKA ALONG WITH STORM AND
GALE FORCE WINDS OVER MARINE AREAS. STRONG WINDS COMBINED WITH SNOW
WILL PRODUCE BLIZZARD CONDITIONS ACROSS PORTIONS OF THE KENAI PEN AND
ALONG THE NORTHERN GULF FRI AND FRI NIGHT. HEAVY SNOW POTENTIAL ALSO
EXISTS FOR THE SUSITNA VALLEY AND ALONG PORTIONS OF THE NORTH GULF
COAST WITH STRONG UPSLOPE FLOW (SEE WARNING STATEMENTS FOR DETAILS ON
CURRENT WWA). CONDITIONS WILL IMPROVE ACROSS MUCH OF THE AREA WITH
THE PASSAGE OF THE SURFACE FRONT SAT MORNING.

.SW ALASKA...
WINDS ARE STARTING TO INCREASE OVER THE DELTA AND WILL SPREAD TO
BRISTOL BAY THIS EVENING. SNOW AND BLOWING SNOW IS EXPECTED TO
PROGRESS EAST ACROSS THE DELTA AND BRISTOL BAY TONIGHT PRODUCING
BLIZZARD CONDITIONS IN ZONES 155 AND 161. THERE MAY SEE SOME MIXED
RAIN AND SNOW ALONG COASTAL AREAS...BUT COLD AIR INLAND AND POCKETS
OF COLD AIR ALONG THE COASTS SHOULD HOLD IN TONIGHT. HEAVY SNOW IS
ALSO POSSIBLE OVER PORTIONS OF THE NORTHERN BRISTOL BAY ZONE WEST OF
KING SALMON TONIGHT. CONDITIONS OVER MUCH OF THE AREA WILL IMPROVE
AFTER FRONTAL PASSAGE EARLY FRI MORNING. SNOW SHOWERS WITH SOME
BRISK WINDS WILL BE THE GENERAL RULE ON FRI AND INTO SAT.

BERING SEA/ALEUTIANS/AK PEN...STRONG SOUTHERLY AND WESTERLY WINDS
WILL GIVE WAY TO STRONG WEST AND NW WINDS AND FRI AND SAT OVER MUCH
OF THE BERING SEA/ALEUTIANS. STRONG NORTHERLY WINDS ARE EXPECTED TO
SPREAD TO THE WESTERN AK PEN ON SAT AFTERNOON. RAIN AND SNOW SHOWERS
WILL BE THE GENERAL RULE OVER MUCH OF THE AREA FRI AND SAT.

.LONG TERM FORECAST...SNOW WINDING DOWN SAT S-CENTRAL AS FRONT
MOVES E AND TRIPLE POINT LOW MOVES INLAND. STRONG GUSTY N TO NW
WINDS EASTERN ALEUTIANS AND AK PEN ON BACK SIDE OF LOW SAT ALONG
WITH SNOW SHOWERS. ANOTHER WAVE ON FRONT IN NPAC WILL MOVE N SUN
AND ROLL BACK W ALONG GULF COAST AS UPPER RIDGE AMPLIFIES OVER
BC/SE AK...BRINGING RAIN AND GALES...WITH SOME SNOW POSSIBLE
INLAND OVER S-CENTRAL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 121 125 155 161
         BLIZZARD WARNING 155
         HIGH WIND WARNING 101
         BLIZZARD WATCH 131 AND 135.
         WINTER STORM WATCH HEAVY SNOW 145
MARINE...STORMS 411 413 175 176 130 132
         GALES 412 414 150 155 160 165 180 170 172 179 185
               351 352 127 128 120 125 129 138 140 141
FIRE WEATHER...NONE.

RMC DEC 10