Storm Warning 257, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST MON DEC 13 2010

.ANALYSIS AND UPPER LEVELS...
A STABLE WEATHER PATTERN CONTINUES ACROSS THE REGION THIS AFTERNOON.
A STRONG BLOCKING HIGH PRESSURE RIDGE REMAINS SITUATED OVER THE
CENTRAL BERING. A SMALL BUT POTENT SHORTWAVE TROUGH PROGRESSING
QUICKLY DOWN THE EASTERN SIDE OF THE RIDGE IS BRINGING SNOW SHOWERS
TO SOUTHWEST ALASKA AND CLOUDS TO THE REST OF SOUTH CENTRAL ALASKA.
AT THE SURFACE...A HIGH PRESSURE CELL IS STACKED UNDER ITS UPPER
LEVEL COUNTERPART OVER THE CENTRAL BERING. A TIGHTLY WOUND SURFACE
LOW OVER THE KUSKOKWIM DELTA IS SHOWING UP QUITE NICELY ON THE BETHEL
RADAR AS IT TRACKS QUICKLY SOUTHEASTWARD. MORE WIDESPREAD AND HEAVIER
AREAS OF SNOW ARE OCCURRING IN THE VICINITY OF THIS LOW. FINALLY...A
BROAD AND VERY WEAK REGION OF LOW PRESSURE PERSISTS IN THE GULF.

.MODEL DISCUSSION...
MODELS CONTINUE TO BE IN OVERALL GOOD AGREEMENT THROUGH THE SHORT
TERM. THE MODELS ARE COMING TOGETHER ON THE PLACEMENT OF A COLD UPPER
LEVEL ARCTIC LOW THAT BEGINS DESCENDING ACROSS THE STATE TONIGHT AND
TOMORROW...THOUGH THE UKMET STILL REMAINS AN OUTLIER. TOWARDS THIS
WEEKEND SOME DISCREPANCIES BEGIN DEVELOPING WITH REGARDS TO THE
STRUCTURE OF THE BERING HIGH...BUT OVERALL FORECAST CONFIDENCE IS
VERY GOOD THROUGH THE END OF THE WEEK. TODAY'S FORECAST USED A BLEND
OF THE NAM AND GFS.

.SHORT TERM FORECAST...THE MAJOR WEATHER ITEM OVER THE NEXT DAY IS
THE SHORT WAVE MOVING THROUGH FROM THE WEST NORTHWEST. THIS LOW WILL
BRING SOME SNOW INTO THE KUSKOKWIM VALLEY AND BRISTOL BAY REGION
THROUGH THE EVENING AND THEN INTO THE COOK INLET AREA AFTER MIDNIGHT
AND INTO THE EARLY MORNING HOURS. AFTER THIS WAVE MOVES THROUGH IS
WHEN THE PRESSURE GRADIENT WILL REALLY INCREASE AND BRING GUSTY
NORTHERLY WINDS TO MOST OF THE AREA.
EXPECT LOW WIND CHILLS OVER MUCH OF THE REGION AS WELL WITH THE COLD
AMBIENT TEMPERATURES AND GUSTY WINDS.
STRONGEST WINDS WILL LIKELY BE IN THE EASTERN PRINCE WILLIAM SOUND
REGION AND THROUGH THE COPPER RIVER DELTA. THERE IS A HIGH WIND
WARNING FOR THOSE AREAS TUESDAY AFTERNOON THROUGH WEDNESDAY
AFTERNOON. THOMPSON PASS IS LIKELY TO SEE THE WORST OF THE CONDITIONS
WITH WIND CHILLS THAT MAY APPROACH 50 BELOW ZERO DURING THE HIGH WIND
EVENT.

.LONG TERM FORECAST...COLD AIR WILL ARRIVE ACROSS ALL OF SOUTHERN
MAINLAND ALASKA BY TUESDAY. THIS WILL BEGIN A COLD, BREEZY, BUT SUNNY
WEEK FOR MOST OF THE AREA. RELATIVELY WARM AND DRY CONDITIONS WILL
CONTINUE TO PREVAIL FOR THE GENERAL BERING SEA REGION THROUGH THE
WEEK AND INTO NEXT WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 131 135.
MARINE...GALE 121 125 130 132 140 141 150 155 160 165 171 176 179
              180.
         HEAVY FREEZING SPRAY 121 140 141.
FIRE WEATHER...NONE.

KS/EZ DEC 10