Heavy Freezing Spray Warning 220, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SUN DEC 2 2012

.ANALYSIS AND UPPER LEVELS...
THE AMPLIFIED UPPER LEVEL PATTERN CONTINUES THIS AFTERNOON WITH
PERSISTENT RIDGING OVER THE BERING SEA AND A TROUGH EXTENDING FROM
THE YUKON TERRITORY INTO THE EASTERN GULF OF ALASKA. BROAD NORTHERLY
FLOW BETWEEN THESE TWO FEATURES CONTINUES TO PROMOTE COLD AND DRY
CONDITIONS OVER MUCH OF SOUTHERN MAINLAND ALASKA. A SERIES OF
DISTURBANCES EMBEDDED IN THE NORTHERLY FLOW AS WELL AS A 120 KT UPPER
LEVEL JET DIGGING ALONG THE WESTERN PERIPHERY OF THE TROUGH ARE
SUPPORTING SNOW ALONG THE AKPEN AND RAIN OVER THE EASTERN
ALEUTIANS...WITH A FEW ADDITIONAL SNOW SHOWERS ALONG MAINLY COASTAL
PORTIONS OF THE WESTERN MAINLAND.

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD AGREEMENT WITH THE HANDLING OF OVERALL SYNOPTIC
FEATURES THROUGH THE SHORT TERM. THE BERING RIDGE WILL FINALLY BREAK
DOWN BY TUESDAY AFTERNOON AS IT IS ERODED BY AN APPROACHING UPPER LOW
FROM THE WEST. THIS WILL ALLOW THE TROUGH TO SHIFT WESTWARD OVER
MAINLAND ALASKA...WITH AN UPPER LOW DROPPING INTO THE GULF ON MONDAY
FOLLOWED BY THE DEVELOPMENT OF ANOTHER CLOSED LOW OVER THE NORTHERN
AKPEN/KODIAK ISLAND ON TUESDAY AFTERNOON. MODELS BEGIN TO DIVERGE
SIGNIFICANTLY OVER THE LATTER HALF OF THE WEEK...PARTICULARLY OVER
WESTERN PORTIONS OF THE FORECAST AREA.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
MORE OF THE SAME IS IN STORE FOR SOUTHCENTRAL AK...WITH COLD AND DRY
CONDITIONS PREVAILING THROUGH THE EARLY PART OF THE WEEK FOR MOST OF
THE AREA. THE COMBINATION OF COLD AIR IN PLACE AT THE SURFACE OVER
THE COPPER RIVER BASIN AND LOW PRESSURE IN THE GULF WILL CONTINUE TO
SUPPORT STRONG GAP WINDS THROUGH FAVORED AREAS. GUSTY WINDS COUPLED
WITH LOW RELATIVE HUMIDITY WILL CONTINUE THE POSSIBILITY OF RED
FLAG CONDITIONS IN THE MATANUSKA VALLEY THROUGH MONDAY AFTERNOON.

SOUTHWEST ALASKA...
ISOLATED SNOW SHOWERS ALONG COASTAL PORTIONS OF THE KUSKOKWIM DELTA
WILL CONTINUE TO TAPER OFF THROUGH THIS EVENING AS AN UPPER LEVEL
DISTURBANCE MOVES SOUTH OF THE AREA...LEAVING PREDOMINANTLY CLEAR AND
COLD CONDITIONS ACROSS THE SOUTHWEST MAINLAND. THE AKPEN WILL
CONTINUE TO SEE SNOW SHOWERS AND STRONG WINDS THROUGH CHANNELED
TERRAIN AS NORTHERLY FLOW PERSISTS INTO THE EARLY PART OF THE WEEK.

ALEUTIANS/BERING SEA...
A FRONT ASSOCIATED WITH A LOW PRESSURE SYSTEM MOVING TOWARD THE
KAMCHATKA PENINSULA WILL CONTINUE TO BRING RAIN TO THE WESTERN
ALEUTIANS TONIGHT...THEN SPREAD RAIN OVER THE CENTRAL ALEUTIANS ON
MONDAY AS IT MOVES EASTWARD.

.LONG TERM FORECAST...
MODELS CONTINUE TO INDICATE A PATTERN CHANGE IN THE EXTENDED TERM AS
THE BERING RIDGE BREAKS DOWN AND ALLOWS A BROAD UPPER LEVEL TROUGH TO
BECOME ESTABLISHED OVER SOUTHCENTRAL ALASKA BY THE MIDDLE OF THE
WEEK. THIS COULD BRING A RETURN OF PRECIPITATION TO THE FORECAST
LATER IN THE WEEK...PRIMARILY ALONG THE GULF COAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...STORM WARNING 130
         GALE WARNING 121 126 127 128 129 132 150 155 160 165 176
         HEAVY FREEZING SPRAY WARNING...121 126 127 129 130 138 140
                                        141 150 160
FIRE WEATHER...RED FLAG WARNING 111

CB DEC 12