Blizzard in Alaska, December 15 to 17, 2009

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKST TUE DEC 15 2009

.MODEL DISCUSSION...MODELS ARE SETTLING DOWN AND SEEM TO HAVE A GOOD
HANDLE ON THE OVERALL PATTERN. THE BIGGEST DIFFERENCE IN MODELS IS IN
THE WAY THE GFS AND NAM ARE DEPICTING THE LOW AS IT MOVES FROM PRINCE
WILLIAM SOUND AND TO THE NORTH ON WEDNESDAY. THE GFS IS BRINGING THE
LOW INTO THE COPPER RIVER BASIN WEDNESDAY NIGHT AND HAS A RESIDUAL
TROUGH EXTENDING OUT OF IT AND BACK OVER THE SOUND AND EASTERN KENAI
PENINSULA. THE NAM TAKES THE SAME TRACK WITH THE MAIN LOW BUT THEN
DEVELOPS A SECONDARY LOW IN THAT TROUGH BETWEEN KENAI AND HOMER
WEDNESDAY NIGHT. THIS SECONDARY LOW IS LIKELY TO BE A KEY IN THE SNOW
FORECASTS IN NOT ONLY THE COOK INLET REGION BUT OVER A LARGER PART OF
SOUTH CENTRAL ALASKA. THE STRONG COLD ADVECTION WITH THIS SYSTEM
MAKES THIS DEVELOPMENT SEEM FAIRLY LIKELY.

.ANALYSIS AND UPPER LEVELS...THE MAINLAND PART OF THE STATE IS UNDER
THE INFLUENCE OF A LONG WAVE TROUGH WITH AN UPPER LEVEL LOW CENTERED
OVER THE BROOKS RANGE. THIS UPPER LOW WILL MOVE SLOWLY SOUTHWARD
UNTIL IT IS OVER NORTHERN COOK INLET THURSDAY. A WEAK UPPER LEVEL
RIDGE OVER THE CENTRAL BERING SEA WILL BREAK DOWN AS THE WEEK
PROGRESSES.
THE SURFACE PATTERN HAS A LOW IN THE SOUTHERN PART OF PRINCE WILLIAM
SOUND AND ANOTHER LOW A FEW HUNDRED SOUTH OF IT IN THE GULF OF
ALASKA. THE LOW IN THE GULF WILL MOVE NORTHWARD AND MERGE WITH THE
OTHER LOW IN THE SOUND WEDNESDAY.

.SHORT TERM FORECAST...THERE IS LOTS OF WEATHER...ESPECIALLY
SNOW...EXPECTED EAST OF THE ALASKA RANGE TODAY THROUGH WEDNESDAY. THE
UPPER LEVEL FLOW IS BRINGING MOISTURE STRAIGHT INTO PRINCE WILLIAM
SOUND AND THERE SHOULD BE CONTINUOUS SNOW IN THE VALDEZ AND CORDOVA
AREAS THROUGH WEDNESDAY NIGHT. THE THERMAL PACKING IN THE COOK INLET
AREA IS CONDUCIVE FOR PERIODS OF SNOW TO PERSIST THROUGH WEDNESDAY
AFTERNOON. WINDS WILL BRING BLOWING SNOW TO THOMPSON PASS WHERE A
BLIZZARD WARNING WILL BE IN EFFECT INTO WEDNESDAY. WINDS WILL ALSO
DROP WIND CHILLS THROUGH THE ALASKA RANGE PASSES AND BRING HEAVY
FREEZING SPRAY INTO THE KODIAK AREA AND AROUND THE ALASKA PENINSULA
AND SOUTHWEST ALASKA COAST.
WEST OF THE ALASKA RANGE...WIND CHILLS BEING THE BIGGEST CONCERN WITH
INCREASING WINDS AND COLD AIR ADVECTION TONIGHT THROUGH WEDNESDAY
NIGHT. WIND CHILL ADVISORIES FOR 40 BELOW ZERO READINGS REMAIN IN
EFFECT IN THE BRISTOL BAY AREA...THE KUSKOKWIM DELTA...AND PARTS OF
THE LOWER KUSKOKWIM VALLEY.

.LONG TERM FORECAST...THE COLD AIR OVER THE MAINLAND PART OF THE
STATE WILL LINGER THROUGH MOST OF THE WEEK. AN INTENSE LOW IS
EXPECTED TO DEVELOP SOUTHWEST OF THE ALEUTIANS AND MOVE INTO THE
WESTERN AND CENTRAL ALEUTIANS THURSDAY NIGHT INTO FRIDAY. THIS LOW
WILL BRING A BIT OF WARM AIR WITH IT AND BEGIN TO DISPLACE THE COLDER
AIR OVER THE STATE AS THE LOW MOVES EASTWARD OVER THE WEEKEND. THERE
IS THE POSSIBILITY OF RAIN MAKING IT INTO BRISTOL BAY AND THE GULF
COAST BY LATE IN THE WEEKEND. THERE IS ALSO THE POSSIBILITY OF A
CHINOOK IN SOUTH CENTRAL EARLY NEXT WEEK IF THIS FORECAST PATTERN
PERSISTS...BUT IT IS STILL TOO EARLY TO BE CERTAIN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD 131.
MARINE...GALE 132 138 150
   STORM 130
   HEAVY FREEZING SPRAY 130 132 138 140 141 150 160 165 179 180 185
FIRE WEATHER...NONE.

DEC 09