Heavy Freezing Spray Warning 196, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKST THU NOV 22 2012

.ANALYSIS AND UPPER LEVELS...
THE GENERAL UPPER LEVEL PATTERN REMAINS THE SAME THIS
AFTERNOON...WITH A LONGWAVE RIDGE OVER THE BERING SEA AND AN UPPER
LEVEL TROUGH ENCOMPASSING MUCH OF MAINLAND ALASKA AS BROAD NORTHERLY
FLOW PERSISTS OVER WESTERN ALASKA AND THE EASTERN BERING BETWEEN
THESE TWO FEATURES. AS A RESULT...CALM WEATHER CONDITIONS PERSIST
OVER MUCH OF THE REGION WITH WIDESPREAD SUNNY AND COLD CONDITIONS
ACROSS THE SOUTHERN MAINLAND AND OVERCAST SKIES OVER THE BERING.
MEANWHILE...A POWERFUL VERTICALLY STACKED LOW PRESSURE SYSTEM IS
CURRENTLY ENTERING THE EASTERN GULF OF ALASKA WITH A SURFACE PRESSURE
NEAR 960 MB. THE TIGHTENING OF THE SURFACE PRESSURE GRADIENT IN
RESPONSE TO THE NORTHWARD MOVEMENT OF THIS SYSTEM WILL LEAD TO THE
DEVELOPMENT OF STRONG GAP WINDS THIS EVENING OVER FAVORED AREAS OF
SOUTHCENTRAL ALASKA.

.MODEL DISCUSSION...
MODELS CONTINUE TO BE IN GOOD AGREEMENT THROUGH THE SHORT TERM BUT
BEGIN TO DIVERGE THEREAFTER. THERE REMAINS A STRONG CONSENSUS IN THE
HANDLING OF THE SYSTEM OVER THE EASTERN GULF...DEPICTING A GRADUAL
WEAKENING TREND AS IT MOVES NORTH AND EASTWARD OVER THE NEXT TWO
DAYS...WITH THE CLOSED UPPER LOW THEN TRANSITIONING TO AN OPEN WAVE
AS IT REACHES THE SOUTHERN PANHANDLE ON SATURDAY AFTERNOON AND
EVENTUALLY DISSIPATING.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE MAIN SHORT TERM FORECAST CONCERN ACROSS SOUTHCENTRAL AK CONTINUES
TO BE THE STRONG GAP WINDS DEVELOPING THIS AFTERNOON AS THE DEEP GULF
LOW CONTINUES ITS NORTHWARD PROGRESSION. WITH A VERY COLD SURFACE AIR
MASS REMAINING IN PLACE OVER THE INTERIOR...THE PRESSURE GRADIENT
WILL CONTINUE TO TIGHTEN THIS AFTERNOON AND EVENING IN RESPONSE TO
THE APPROACHING LOW...RESULTING IN STRONG GAP WINDS DEVELOPING IN
FAVORED AREAS SUCH AS THE MATANUSKA VALLEY...WHITTIER...SEWARD...AND
PARTICULARLY VALDEZ AND THE COPPER RIVER DELTA. WINDS WILL BEGIN TO
DIMINISH TOWARDS FRIDAY MORNING AS THE GULF LOW BEGINS TO WEAKEN AND
MOVE OFF TO THE EAST...BUT WILL REMAIN GUSTY THROUGH THE DAY ON
FRIDAY. ASIDE FROM THE WIND ISSUES...CALM CONDITIONS CHARACTERIZED BY
CLEAR SKIES AND COLD TEMPERATURES WILL PERSIST ACROSS SOUTHCENTRAL AK
THROUGH THE WEEKEND.

SOUTHWEST ALASKA...
MORE OF THE SAME FOR THE SOUTHWEST MAINLAND AS CLEAR AND COLD
CONDITIONS WILL PERSIST THROUGH THE WEEKEND. BREEZY WINDS OUT OF THE
NORTH WILL CONTINUE TO SUPPORT WIND CHILL VALUES APPROACHING 30 BELOW
ZERO THROUGH FRIDAY NIGHT. THE AKPEN WILL SEE GUSTY NORTHERLY WINDS
AND PERHAPS A FEW SNOW SHOWERS INTO SATURDAY MORNING.

ALEUTIANS/BERING SEA...
A LOW PRESSURE SYSTEM OVER THE NORTHERN PACIFIC WILL BRING RAIN TO
THE WESTERN AND CENTRAL ALEUTIANS THROUGH THE DAY ON FRIDAY BEFORE
DIVING SOUTH OF THE CHAIN. AFTER A BRIEF LULL...PRECIPITATION WILL
RETURN ON SATURDAY WITH THE ARRIVAL OF THE NEXT SYSTEM INTO THE
WESTERN BERING. ACROSS THE EASTERN ALEUTIANS/BERING...GENERALLY
BENIGN WEATHER WILL PERSIST THROUGH THE WEEKEND UNDER THE INFLUENCE
OF HIGH PRESSURE.

.LONG TERM FORECAST...
AN UPPER LEVEL BLOCKING HIGH LOOKS TO PERSIST OVER THE EASTERN BERING
AND WESTERN ALASKA INTO THE EXTENDED TERM...KEEPING MUCH OF THE
SOUTHERN MAINLAND COLD AND DRY INTO THE MIDDLE OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 131 135
MARINE...STORM WARNING 127 128
         GALE WARNING 120 121 126 130 132 175 176 180
         HEAVY FREEZING SPRAY WARNING 121 127 160 165 180
FIRE WEATHER...NONE

CB NOV 12