Gale Warning 1089, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST MON DEC 27 2010

.ANALYSIS AND UPPER LEVELS...THE LARGE BROAD TROUGH OVER MAINLAND
ALASKA AND THE GULF OF ALASKA IS LOSING AMPLITUDE AS THE ANTICIPATED
UPPER LEVEL PATTERN CHANGE IS UNDERWAY. A VERTICALLY STACKED UPPER
LEVEL LOW EAST OF KODIAK ISLAND IS WEAKENING AND BEGINNING TO MOVE
BACK TO THE EAST. THERE IS ANOTHER WEAK UPPER LOW NEAR BRISTOL BAY
THAT IS QUICKLY WEAKENING TO AN OPEN WAVE. MEANWHILE...PERSISTENT
HIGH PRESSURE OVER THE BERING IS A DISTANT MEMORY AS A RAPIDLY
DEVELOPING CYCLONE IS MOVING INTO THE REGION FROM THE WEST. THE
ASSOCIATED FRONT IS BRINGING STRONG WINDS AND NEAR-BLIZZARD
CONDITIONS TO PARTS OF THE ALEUTIAN ISLANDS THIS MORNING.

.MODEL DISCUSSION...MODELS ARE SLOWLY COMING TO A CONSENSUS WITH THE
DETAILS OF THE DEVELOPING BERING SEA LONGWAVE TROUGH. PREVIOUS TIMING
ISSUES BETWEEN THE EC AND GFS HAVE BEEN SIGNIFICANTLY RESOLVED
TODAY...LEADING TO AN IMPROVEMENT IN FORECAST CONFIDENCE THROUGH THE
END OF THE WEEK FOR MUCH OF THE DOMAIN. AS A SECOND MAJOR SHORTWAVE
ROTATES TOWARD SOUTHCENTRAL ALASKA FOR THE START OF THE
WEEKEND...MODELS CONTINUE TO STRUGGLE ON SOME ASPECTS OF POSITION AND
INTENSITY OF THE FEATURE. THUS MODEL CONFIDENCE REMAINS SLIGHTLY
BELOW AVERAGE FOR THE MID AND LONG RANGE FORECAST. BASED ON THE
COMPLEXITY OF THE FORECAST...A COMBINATION OF MODELS WAS USED IN THE
SHORT TERM. FOR THE MID AND LONG RANGE...A COMBINATION OF HPC
GUIDANCE AND THE 00Z EUROPEAN MODEL WAS USED IN THE MORNING FORECAST
PACKAGE.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...AS LOW PRESSURE CONTINUES TO SPIN IN THE GULF
SCATTERED SNOW SHOWERS WILL CONTINUE PRIMARILY OVER COASTAL AREAS AND
KODIAK ISLAND. AS THE COMPLEX LOW IN THE GULF SLIDES EASTWARD THROUGH
THIS EVENING...MODELS ARE COMING INTO AGREEMENT NOW THAT A WEAK LOW
WILL LINGER OFF THE COAST OF THE KENAI PENINSULA. THIS WILL BE
ABSORBED INTO THE APPROACHING BERING FRONT THAT IS RACING TO THE
NORTHEAST AND WILL USHER IN A PERIOD OF PRECIPITATION TO MUCH OF THE
REGION AS WARM AIR BEGINS TO MOVE INTO THE REGION ALOFT. BEST BET
RIGHT NOW IS THAT LIGHT SNOW WILL DEVELOP EARLY WED MORNING AND
CONTINUE THROUGH MUCH OF THE DAY WEDNESDAY. SNOWFALL TOTALS SHOULD BE
LIGHT AT MOST PLACES...WITH ONLY AN INCH OR TWO EXPECTED IN THE
ANCHORAGE AREA.

THE FORECAST BECOMES MORE COMPLICATED BY THURSDAY AS THE CURRENT
BERING LOW WEAKENS AND MOVES TOWARD COOK INLET. WIDESPREAD ISENTROPIC
LIFT GIVES WAY TO MORE DYNAMIC FEATURES AS WINDS INCREASE ACROSS THE
REGION AS WELL. AT THIS TIME IT IS DIFFICULT TO KNOW IF THE CLASSIC
DOWNSLOPING PATTERN IN ANCHORAGE WILL OCCUR AS THE MAIN LOW
APPROACHES. THESE DETAILS WILL HAVE TO BE FINE-TUNED IN SUBSEQUENT
FORECAST PACKAGES.

.SOUTHWEST...PARTLY CLOUDY SKIES WILL GIVE WAY TO INCREASING CLOUDS
ON WEDNESDAY AS BERING SEA SYSTEM MOVES TOWARD THE AREA. IN THE
MEANTIME...EXTREME COLD TEMPERATURES WITH BREEZY NORTHEASTERLY WINDS
WILL CONTINUE. THIS WILL BE ESPECIALLY TRUE ACROSS THE KUSKOKWIM
DELTA WHERE WIND CHILLS ARE NEAR 35 BELOW THIS MORNING. CONDITIONS
SHOULD CONTINUE JUST BELOW ADVISORY CRITERIA THROUGH WEDNESDAY
MORNING BEFORE CLOUDS BEGIN TO MOVE INTO THE AREA AND WARM UP
TEMPERATURES.

.BERING SEA AND ALEUTIANS...STORM-FORCE WINDS AND NEAR-BLIZZARD
CONDITIONS WERE OBSERVED OVERNIGHT IN THE CENTRAL ALEUTIANS.
TEMPERATURES HAVE NO WARMED TO NEAR FREEZING...RAISING VISIBILITIES
ACROSS THE REGION. WITH CONTINUED WARM AIR ADVECTION THE THREAT OF
SIGNIFICANTLY REDUCED VISIBILITIES SHOULD BE PAST...THUS HAVE OPTED
TO CANCEL THE BLOWING SNOW ADVISORY THIS MORNING. THIS WEATHER FRONT
WILL GENERALLY PARALLEL THE ALEUTIANS AS IT SLIDES NORTHEAST OVER THE
NEXT SEVERAL DAYS. THUS THE BAROCLINIC ZONE WILL SET UP JUST NORTH OF
THE ALEUTIAN CHAIN...ALLOWING PRECIPITATION TO MIX WITH OR CHANGE TO
RAIN AT LOCATIONS FROM THE CENTRAL ALEUTIANS TO THE ALASKA PENINSULA.
MEANWHILE...EXPECT STRONG NORTHEASTERLY WINDS TO CONTINUE THROUGHOUT
THE NORTHERN AND WESTERN BERING THROUGH THURSDAY.

.LONG TERM FORECAST...WHILE CONFIDENCE IN THE UPPER LEVEL PATTERN IS
INCREASING FOR THIS WEEKEND AND BEYOND...MANY CRITICAL DETAILS OF THE
FORECAST REMAIN UNANSWERED. HOWEVER...ALL SIGNS POINT TO A WARMER AND
SNOWIER PATTERN OVER MAINLAND ALASKA AND CONTINUED COLD NORTHERLY
FLOW OVER THE BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WIND CHILL ADVISORY 131
MARINE...STORM 175 176
         GALE 170 172 179
         HEAVY FREEZING SPRAY 160 179 185
FIRE WEATHER...NONE

AMD DEC 10