Heavy Freezing Spray Warning 73, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST TUE FEB 28 2012

.ANALYSIS AND UPPER LEVELS...

WEAK STATIONARY LOW REMAINS ACROSS THE NORTH CENTRAL GULF OF
ALASKA...AND WILL REMAIN THERE AND WEAKEN THROUGH WEDNESDAY. DIGGING
UPPER LEVEL LOW OVER SOUTHWEST ALASKA DIGGING SOUTH AND EAST
SUPPORTED BY A POWERFUL UPPER LEVEL NORTHWESTERLY JET STREAK OVER THE
BRISTOL BAY REGION. VERY COLD TEMPERATURES AND STRONG WINDS ARE
SUPPORTING WIND CHILL ADVISORY CRITERIA OVER PARTS OF SOUTHWEST
ALASKA THIS MORNING.

OVER SOUTHCENTRAL...THE INTERACTION OF THESE TWO PRINCIPAL UPPER
LEVEL LOWS IS KEEPING AN AREA OF DEFORMATION OVER PARTS OF
SOUTHCENTRAL ALASKA FROM THE KENAI PENINSULA NORTH AND WEST TO THE
SOUTHWESTERN SUSITNA VALLEY. THIS ALSO INCLUDES
ANCHORAGE...ESPECIALLY THE FAR WESTERN SIDE OF TOWN...WHERE LIGHT
SNOW HAS BEEN CONTINUOUS ALL NIGHT WITH ONLY MINOR ACCUMULATIONS.

OUT IN THE BERING...THE BIG STORY IS THE POWERFUL WINDS ASSOCIATED
WITH LOW PRESSURE OVER THE WESTERN BERING SEA AND ITS ASSOCIATED
FRONT. WINDS ARE MAXING OUT AT LOW END HURRICANE FORCE CURRENTLY. THE
LOW ASSOCIATED WITH THIS FRONT WILL MOVE NORTH AND THEN WEST TOWARDS
EASTERN RUSSIA OVER THE NEXT 24 HOURS...WHILE ITS ASSOCIATED FRONT
WILL LOSE ITS UPPER LEVEL SUPPORT AND WEAKEN OVER THE CENTRAL
BERING...PRIBILOFS ISLANDS...AND SOUTHERN ALASKA PENINSULA OVER THE
NEXT 24 HOURS.

.MODEL DISCUSSION...

MODELS ARE IN GREAT AGREEMENT IN THE SHORT TERM. A BLEND OF MODELS
WAS EMPLOYED DEPENDING ON WHICH MODEL WAS THOUGHT TO BE BEST HANDLING
A PARTICULAR WEATHER PARAMETER.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

MAIN AREA OF CONCERN IS THE WEAK AREA OF DEFORMATION OVER THE COOK
INLET REGION AND THE KENAI PENINSULA. THIS HAS BEEN A PERSISTENT
FEATURE FOR SOME TIME...AND GIVEN THE MODEL AGREEMENT WILL LIKELY
CONTINUE TO PESTER THE REGION INTO WEDNESDAY. THE GULF UPPER LEVEL
LOW WILL LIKELY DISSIPATE BY WEDNESDAY WHILE THE LOW OVER SOUTHWEST
ALASKA WILL CUT OFF AND REMAIN NEARLY STATIONARY OR DRIFT EASTWARD
INTO THE COOK INLET REGION WEDNESDAY INTO WEDNESDAY NIGHT. WILL
CONTINUE TO RELY A LOT ON PERSISTENCE AND ADVERTISE CHANCE TO
CATEGORICAL SNOW PROBABILITIES FOR THE COOK INLET REGION AND PRINCE
WILLIAM SOUND FOR THE NEXT 12 TO 36 HOURS...WITH ACCUMULATIONS
REMAINING MINOR.

SOUTHWEST ALASKA...

PERSISTENT UPPER LEVEL RIDGING ALOFT OVER THE CENTRAL AND EASTERN
BERING SEA AND A NEARLY STATIONARY UPPER LEVEL LOW OVER THE CHIGMIT
MOUNTAINS WILL CONTINUE TO BE ACCOMPANIED BY A STRONG NORTHWESTERLY
JET STREAK OVER THE BRISTOL BAY REGION. THIS WILL CONTINUE TO HELP
POOL A VERY COLD AIR MASS OVER SOUTHWEST ALASKA...WITH WIND CHILLS
APPROACHING 30 BELOW TO 40 BELOW WITH STRONG WINDS IN EXPOSED LOCALES
THIS MORNING. SKIES WILL REMAIN MOSTLY CLEAR INLAND THROUGH MID
WEEK...AND WINDY ESPECIALLY THROUGH OUTFLOW CHANNELS ALONG THE
CHIGMIT MOUNTAINS OF THE ALEUTIAN RANGE.

BERING SEA/ALEUTIANS...

HURRICANE FORCE WINDS WILL ACCOMPANY LOW PRESSURE OVER THE WESTERN
BERING THROUGH THIS AFTERNOON BEFORE THAT LOW MOVES NORTH AND THEN
WEST TOWARDS EASTERN RUSSIA TONIGHT. BLIZZARD WARNING FOR THE
PRIBILOFS WILL BE ALLOWED TO CONTINUE WITH THE MORNING PACKAGE...AS
WINDS ARE ALREADY AT BLIZZARD CRITERIA. MAIN LIMITING FACTOR MAY BE
SNOW ACCUMULATIONS...AS THEY WILL BE MINOR. THIS FRONT WILL CONTINUE
TO WEAKEN THROUGH TONIGHT AS IT ENCOUNTERS STRONG RESISTANCE WITH
RIDGING HOLDING FIRM OVER THE EASTERN BERING...BUT IT TOO WILL WEAKEN
ALONG WITH THE FRONT. NEW LOW PRESSURE SYSTEM DEVELOPS TONIGHT AND
MOVES RAPIDLY TOWARDS THE CENTRAL ALEUTIANS WITH A LARGE AREA OF
STORM FORE WINDS LATE TONIGHT...THEN SLIDES EAST ACROSS THE ISLAND
CHAIN HEADED FOR THE GULF THROUGH THURSDAY NIGHT INTO FRIDAY.

.LONG TERM FORECAST...

ACTIVE WEATHER PATTERN WILL REMAIN ON TAP LATE THIS WEEK THROUGH
EARLY NEXT WEEK...WITH LOW PRESSURE SYSTEMS IN THE GULF AND OUT IN
THE VICINITY OF THE ALEUTIANS FOR MOST OF THIS PERIOD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...195
MARINE...GALES...132 138 150 170 171 175 185 179 414
         STORMS...130 172 176 412 413
         HURRICANE FORCE...411
         HVY FRZG SPRY...121 130 132 138 140 150 179 412 414
FIRE WEATHER...NONE.

29/CC FEB 12