Heavy Snow in Alaska, December 22 to 26, 2012

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST SAT DEC 22 2012

.MODEL DISCUSSION...
MOST OF THE MODELS WERE IN GOOD AGREEMENT EARLY ON HOWEVER LATE IN
THE SHORT TERM THE NAM QUICKLY BECAME AN OUTLIER WITH THE LOW FORMING
IN THE WESTERN GULF. IT HAD THE LOW MOVING MUCH FASTER WEST THAN THE
OTHER MODELS. MOVING OUT INTO THE MID RANGE THE GLOBAL MODELS WERE
HANDLING THINGS WELL BUT STARTED TO DRIFT IN THE LONG RANGE.
CONFIDENCE QUICKLY DROPPED IN THE LONG TERM AS THE MODELS FELL OUT OF
SYNC.

.ANALYSIS AND UPPER LEVELS...
WEAKENING HIGH PRESSURE RESTS OVER THE NORTHERN PART OF THE STATE
WITH RIDGING EXTENDING DOWN ALONG THE WEST COAST AND OVER THE ALASKA
PENINSULA. AN UPPER LEVEL LOW SITS TO THE EAST OF THIS RIDGING IN THE
GULF AND IS BRINGING AN AREA OF INSTABILITY WESTWARD ACROSS THE
SOUTHCENTRAL. A RAPIDLY DIMINISHING FRONT REMAINS OVER THE EASTERN
BERING TO THE WEST OF THE RIDGE. FURTHER WEST HIGH PRESSURE IS
BUILDING INTO THE CENTRAL BERING.

.SHORT TERM FORECAST...
SOUTHCENTRAL...MOST OF THE SOUTHCENTRAL IS UNDER THE EFFECTS OF THE
HIGH PRESSURE AND WILL CONTINUE TO BE COLD AND DRY. SOME AREAS
FURTHER TO THE SOUTH WILL SEE IMPACT BY A LOW THAT IS FORMING JUST
EAST OF KODIAK ISLAND. THIS LOW WILL GRADUALLY MOVE SOUTH OF KODIAK
WHERE IT WILL REST UNTIL MONDAY NIGHT WHEN IT DIMINISHES AND PUSHES
OFF TO THE NORTH. THE LOW WILL ALSO BRING SNOW TO PLACES IN KODIAK
AND SOUTHERN AND EASTERN KENAI PENINSULA.

SOUTHWEST ALASKA...HIGH PRESSURE WILL BE THE DOMINANT FEATURE FOR THE
AREA THROUGHOUT THE DAY KEEPING SKIES CLEAR AND TEMPERATURES COLD.
TODAY A LOW WILL FORM NEAR KODIAK ISLAND THAT WILL START TO BRING
CLOUD COVER AND THE POTENTIAL FOR SNOW TO AREAS FURTHER SOUTH
OVERNIGHT. THAT LOW WILL THEN MOVE INTO THE EASTERN BERING ON MONDAY
WHICH WILL BRING LIGHT SNOW TO MANY AREAS IN SOUTHWEST ALASKA.

BERING SEA AND ALEUTIAN ISLANDS...THE DIMINISHING FRONT OVER THE
EASTERN ALEUTIANS AND ALASKA PENINSULA IS BRINGING SNOW TO THESE
AREAS AS WELL BUT WILL BE SHORT LIVED AS THE FRONT WILL DISSIPATE
THIS AFTERNOON. HIGH PRESSURE WILL BE BUILDING INTO THE BERING THAT
WILL REMAIN FOR MOST OF SUNDAY UNTIL A NEW SYSTEM APPROACHES THE
WESTERN ALEUTIANS SUNDAY. THE ASSOCIATED FRONT WILL MAKE IT TO THE
WESTERN ALEUTIANS BY SUNDAY EVENING AND TO THE CENTRAL ALEUTIANS BY
MONDAY MORNING.

.LONG TERM FORECAST...
EVEN THOUGH OVERALL CONFIDENCE IS LOW IN THE MODELS IN THE LONG TERM
THERE IS SOME CONSENSUS OF A DEEP LOW MOVING INTO THE ALEUTIANS
SOMETIME TUESDAY NIGHT OR MONDAY MORNING. THIS LOW WILL EVENTUALLY
TRACK INTO THE EASTERN BERING AND BRING STRONGER WINDS AND PRECIP TO
AREAS THROUGHOUT THE ALEUTIANS AND SOUTHWEST ALASKA. THE ASSOCIATED
FRONT IS EXPECTED TO IMPACT AREAS OF THE SOUTHCENTRAL WEDNESDAY INTO
THURSDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALES...127 120 130 138 140 165 170 176
         HEAVY FREEZING SPRAY...126 127 128 121 130 140 141 150 160
                                165 185
FIRE WEATHER...NONE

DWK DEC 12