Blizzard and Heavy Snow in Alaska, December 21 to 23, 2004

AREA FORECAST DISCUSSION SOUTHWEST ALASKA
500 PM AST TUE DEC 21 2004

.DISCUSSION...
ONE MAJOR STORM IS AFFECTING THE ALEUTIANS AND ALASKA PENINSULA AS
THE REMAINS OF AN UPPER LEVEL TROUGH MOVES THROUGH SOUTHWEST ALASKA
TO PRINCE WILLIAM SOUND. THE UPPER TROUGH RESULTED IN AN OVER RUNNING
SNOW EVENT ALONG THE GULF COAST REGIONS TO SOUTH CENTRAL ALASKA TO
BRISTOL BAY. WARMER AIR OVER THE ALASKA PENINSULA AND EASTERN
ALEUTIANS KEPT THE PRECIPITATION AS RAIN FOR THOSE REGIONS. THE
COMBINATION OF STRONG NORTH WIND AND LIGHT SNOW RESULTED IN MINIMAL
BLIZZARD CONDITIONS AT SAINT PAUL WHILE THE REST OF THE PRIBILOFS
REMAINED IN MORE FAVORABLE CONDITIONS. CURRENT CONDITIONS SINCE
MIDNIGHT HAVE BEEN OF POOR VISIBILITIES IN SNOW AND BLOWING SNOW, BUT
BETTER THAN MON EVENING. WE EXPECT ANOTHER SHOT OF BLIZZARD
CONDITIONS TO OCCUR AGAIN THIS EVENING AS MORE SNOW AND CONTINUED
WINDS ARE EXPECTED THROUGH THE TUE NIGHT. THE SURFACE LOW NOW SOUTH
OF ADAK IS EXPECTED TO MOVE  TO NEAR CAPE SARICHEF THIS EVENING WITH
THE PRIBILOF ISLANDS IN THE SNOW REGION OF THIS STORM BY MIDNIGHT.
THE CONTINUATION OF WARM ADVECTION INTO THE BRISTOL BAY ZONE, KODIAK
ISLAND AND THE OUTER COASTAL REGION OF SOUTHWEST PRINCE WILLIAM SOUND
SHOULD KEEP THE MAJORITY OF PRECIPITATION AS RAIN OR RAIN AND SNOW
ACROSS THESE AREAS TONIGHT. AS THE LOW AND ASSOCIATED FRONT APPROACH
THE ALASKA PENINSULA AND ALONG THE GULF COAST REGIONS EXPECT A
TIGHTENING OF THE GRADIENT TO RESULT IN STRONG EAST WINDS. THE
TYPICAL ACCELERATED FLOW THROUGH PORTAGE PASS WILL GENERATE TURNAGAIN
ARM WINDS AND WE ALSO EXPECT WINDY CONDITION ACROSS THE CHUGACH
MOUNTAINS THAT IS TYPICAL WITH THESE STORMS. ALONG WITH THE STRONG
SOUTHEAST FLOW WE EXPECT HEAVY SNOW ALONG THE ALASKA RANGE TO BEGIN
THIS EVENING AND SPREAD THROUGHOUT THE ENTIRE SUSITNA VALLEY. THE
INFLUX OF WARM AIR IS EXPECTED TO CHANGE THE SNOW OVER TO RAIN SOUTH
OF TALKEETNA WED, BUT CONTINUED MODERATE TO HEAVY SNOW IS EXPECTED
NORTH OF TALKEETNA WED.

THE MAIN QUESTION THU IS HOW FAST WILL THE SUPPORTING UPPER LEVEL
TROUGH ASSOCIATED WITH THIS STORM MOVE THROUGH SOUTH WEST AND THEN
SOUTH CENTRAL ALASKA. AT THIS POINT WE ARE FAVORING A BLEND OF THE
UKMET AND ETA OVER THE GFS. THE GFS APPEARS TO BE TO FAST IN MOVING
THIS TROUGH EAST. AS A RESULT, THE MAIN ENERGY WILL NOT REMAIN ALONG
THE NORTH GULF COAST AS THE UKMET AND ETA HAVE RESOLVED. THE ETA AND
UKMET SOLUTIONS A FAVORABLE TO A MORE SIGNIFICANT SNOW EVENT THU
FIRST ALONG THE WEST SIDE OF THE ALASKA RANGE THEN MOVING INTO SOUTH
CENTRAL ALASKA THU AFTERNOON.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING ZONE 195. HEAVY SNOW WARNING 145.
MARINE...STORM 8 13A 15. GALE 2B 3ABC 4 5AB 6AB 12A 12A1 12B 13B 14.
FIRE WEATHER...DONE.

SAM DEC 04