Heavy Freezing Spray Warning 6, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
520 AM AKST WED JAN 11 2012

.ANALYSIS AND UPPER LEVELS...
A LOOK AT THE MORNING WEATHER MAP REVEALS A LONGWAVE TROUGH
CONTINUING OVER THE BERING SEA...WITH A RIDGE OVER THE WEST COAST OF
BRITISH COLUMBIA AND THE ALASKA PANHANDLE. THE NET EFFECT OF THESE
TWO FEATURES IS SOUTHWESTERLY FLOW BRINGING AMPLE MOISTURE INTO
MAINLAND ALASKA. THE STRONG FRONT THAT IMPACTED SOUTHCENTRAL
YESTERDAY HAS MOVED OFF INTO THE INTERIOR...MEANWHILE A SLOW-MOVING
BAND OF MODERATE SNOW IS LOCATED OVER SOUTHWEST ALASKA WHERE SNOW
ADVISORIES ARE IN EFFECT. FURTHER WEST...A REINFORCING SHOT OF
BITTERLY COLD ARCTIC AIR IS MARCHING EASTWARD THROUGH THE EASTERN
BERING. THIS COLD AIR IS MOVING TO THE EAST IN RESPONSE TO A STRONG
SURFACE HIGH PRESSURE CURRENTLY BUILDING INTO THE CENTRAL BERING.

.MODEL DISCUSSION...
MODELS ARE IN OVERALL EXCELLENT AGREEMENT THIS MORNING ON BOTH THE
LARGE-SCALE WEATHER FEATURES AND SOME OF THE MORE SIGNIFICANT
SMALL-SCALE FEATURES. THIS AGREEMENT IS ESPECIALLY SURPRISING DUE TO
THE FACT THAT THE LONGWAVE PATTERN WILL BE UNDERGOING A TRANSITION
OVER THE NEXT FEW DAYS. THE NEW PATTERN WILL FEATURE HIGH PRESSURE
OVER THE EASTERN BERING WITH DRY NORTHERLY FLOW OVER MAINLAND ALASKA.
THE NAM IS THE OVERALL FAVORED MODEL DUE TO ITS SUPERIOR HANDLING OF
COMPLEX TERRAIN ACROSS SOUTHCENTRAL ALASKA.

.SHORT TERM FORECAST...
SOUTHCENTRAL...PRIMARY FORECAST CHALLENGE WILL BE THE EVOLUTION THE
BAND OF MODERATE SNOW MOVING INTO THE AREA FROM SOUTHWEST ALASKA. IT
IS NOW LOOKING LIKELY THAT MUCH OF SOUTHCENTRAL...INCLUDING
ANCHORAGE...WILL GET A FINAL SIGNIFICANT ACCUMULATION OF SNOW BEFORE
THE PATTERN BECOMES SUNNY AND DRY FOR A PROLONGED PERIOD STARTING
THIS WEEKEND. MODELS ARE IN GOOD AGREEMENT THAT THE TROUGH OVER THE
EASTERN BERING WILL GRADUALLY BECOME NEGATIVELY TILTED AND DIG INTO
THE WESTERN GULF BEFORE CLOSING OFF INTO AN UPPER LOW THURSDAY
AFTERNOON. THIS WILL BRING AN AREA OF BROAD UPWARD MOTION/LIFT TO THE
REGION STARTING THIS EVENING. THE KEY INGREDIENT THAT WILL MAKE THIS
EVENT SO SIGNIFICANT IS THE SURFACE LOW CURRENTLY SOUTH OF KODIAK
ISLAND. THIS LOW MOVES UP INTO PRINCE WILLIAM SOUND BY THIS
EVENING...STALLS...AND SLOWLY DRIFTS BACK TO THE SOUTH AS THE UPPER
LOW DEVELOPS ON THURSDAY. THIS WILL PROVIDE A SOURCE OF MOISTURE TO
THE ATMOSPHERE THAT SHOULD RESULT IN A LONG-DURATION EVENT OF
MODERATE SNOW FROM THE KENAI PENINSULA TO THE ANCHORAGE AREA AND UP
THROUGH THE SUSITNA VALLEY.

SOUTHWEST...BAND OF MODERATE SNOW CURRENTLY EAST OF A LINE FROM
SLEETMUTE TO DILLINGHAM MOVES SLOWLY EASTWARD TODAY...WITH CLEARING
SKIES BEHIND. ANOTHER ROUND OF EXTREMELY COLD AIR IS MOVING INTO THE
KUSKOKWIM DELTA AND WILL SPREAD TO THE REST OF THE SOUTHWEST MAINLAND
THROUGHOUT THE DAY. WITH WINDS EXPECTED TO BE AROUND 15 MPH...EXPECT
WIDESPREAD DANGEROUS WIND CHILLS THROUGH FRIDAY...ESPECIALLY OVER THE
DELTA.

BERING...HIGH BUILDING INTO THE EASTERN HALF OF THE BERING SEA WILL
SET UP SHOP FOR THE BETTER PART OF THE NEXT WEEK...BRINGING
SEASONABLY COOL CONDITIONS AND GENERALLY BENIGN WEATHER. THIS
BUILDING HIGH PRESSURE IS HELPING GENERATE HURRICANE FORCE WINDS
ACROSS PARTS OF THE ALASKA PENINSULA THIS MORNING. THESE SHOULD BE
SHORT-LIVED AS THE HIGH CENTER MOVES EASTWARD THIS MORNING. WAY OUT
WEST...A VERY STRONG LOW WILL DEVELOP THIS AFTERNOON SOUTH OF THE
KAMCHATKA PENINSULA OF RUSSIA AND RAPIDLY DEEPEN TO THE UPPER 930 MB
RANGE. WHILE THE LOW STAYS WELL OUT OF THE ALASKAN DOMAIN...A
SIGNIFICANT FRONT WILL IMPACT THE WESTERN AND CENTRAL ALEUTIANS
THURSDAY AND THURSDAY EVENING. WINDS WILL APPROACH 70 MPH...WITH
GROWING LIKELIHOOD OF HURRICANE FORCE CONDITIONS. FOR NOW WILL ISSUE
A HIGH WIND WATCH FOR THE WESTERN ALEUTIAN ISLANDS.

.LONG TERM FORECAST...
AS MENTIONED ABOVE...A PATTERN CHANGE IS UNDERWAY ACROSS THE ALASKA
DOMAIN. THE NEW PATTERN WILL BE IN PLACE BY THIS WEEKEND AND WILL
FEATURE SUNNY AND DRY CONDITIONS ACROSS MAINLAND ALASKA...WITH ACTIVE
WEATHER CONFINED TO THE WESTERN BERING SEA REGION. LIKELY SIGNIFICANT
FEATURES OF THIS NEW WEATHER PATTERN WILL BE STRONG NORTHERLY WINDS
IN THE USUAL FAVORED COASTAL AREAS OF SOUTHCENTRAL SUCH AS THOMPSON
PASS AND THE MATANUSKA VALLEY. WHILE THIS PATTERN WILL BE COLD FOR
MAINLAND ALASKA...IT SHOULD NOT BE THE BITTER COLD WE HAVE SEEN IN
RECENT WEEKS. NEVERTHELESS...THE PERSISTENT WIND IN MANY AREAS WILL
KEEP THE CHILL OF WINTER NEARBY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 181
         HIGH WIND WATCH 191
         WIND CHILL ADVISORY 155
         SNOW ADVISORY 101 121 145 152 161
MARINE...HURRICANE FORCE 175 176
         STORM 130 172
         GALE 132 138 150 155 160 165 170
         HEAVY FREEZING SPRAY 121 130 132 138 140 150 155 165 179
FIRE WEATHER...NONE

AMD JAN 12