High Wind in Alaska, December 3 to 4, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST SAT DEC 3 2011

.ANALYSIS AND UPPER LEVELS...

MASSIVE UPPER LEVEL RIDGE FROM THE EASTERN BERING TO THE CANADIAN
ROCKIES THIS MORNING WITH AN INTENSE UPPER LOW OVER THE SOUTHERN
BERING. AT THE SURFACE...A DEEPENING LOW IS OVER THE SOUTHERN BERING
WITH A RIDGE OVER THE EASTERN HALF OF MAINLAND AK AND THE GULF OF AK.
A WARM FRONT EXTENDS ZONALLY INTO THE CENTRAL GULF OF AK. A COLD
FRONT IS APPROACHING THE AKPEN AND BRISTOL BAY.

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT AS FAR AS TIMING AND SYSTEM STRENGTH ARE
CONCERNED...BUT THE UNSEASONABLE NATURE OF THE EXTREME WARM ADVECTION
AND ABUNDANT ATMOSPHERIC MOISTURE IS ADDING SEVERAL DEGREES OF
DIFFICULTY TO TEMPERATURE AND...SUBSEQUENTLY...PRECIPITATION TYPE
FORECASTS.

THE DEEP LOW IN THE SOUTHERN BERING WILL MOVE TO THE BERING STRAIT
SUN AFTERNOON. AS IT MOVES NORTH IT WILL BE SURROUNDED BY STORM AND
HURRICANE FORCE WINDS. THE WARM FRONT ASSOCIATED WITH THIS LOW WILL
MOVE INLAND ALONG THE NORTH GULF COAST AND OVER SW AK THIS
AFTERNOON...ACCOMPANIED BY WARM AIR AND PLENTY OF MOISTURE THAT WILL
STRUGGLE TO OVERCOME THE ENTRENCHED COLD AIR AT THE SURFACE. THE
FOLLOWING COLD FRONT WILL THEN DISPLACE THE WARM MOIST AIR AS IT
CROSSES THE AKPEN LATER THIS AFTERNOON...THE ALASKA RANGE TONIGHT
INTO SUN MORNING...AND THE GULF BY MON MORNING.

IN THE WAKE OF THE BERING LOW...HIGH PRESSURE WILL BUILD OVER THE
BERING THROUGH SUN NIGHT....AND THEN FOLLOW THE COLD FRONT AND BUILD
ACROSS THE EASTERN HALF OF THE FORECAST AREA THROUGH TUE.

THE NEXT NORTH PACIFIC LOW BRINGS ANOTHER FRONT INTO THE WESTERN HALF
OF THE BERING SUN NIGHT WHICH REACHES THE BRISTOL BAY COAST TUE
AFTERNOON.

THE FORECAST UTILIZES A BLEND OF NAM AND GFS IN THE SHORT TERM...AND
THEN HPC GUIDANCE IN THE EXTENDED.

.SHORT TERM FORECAST...

IN THE WEST...EXPECT RAIN AND SNOW WITH STORM AND HURRICANE FORCE
WINDS TODAY...MAINLY AROUND THE LOW. A HIGH WIND WARNING IS IN EFFECT
FOR THE PRIBILOFS TODAY AS THE LOW TRANSITS JUST WEST. SNOW SHOWERS
WILL THEN BE COMMON ACROSS THE BERING AND ALEUTIANS INTO MON...
ALTHOUGH SNOW WILL ACCOMPANY THE NEXT FRONT OVER THE WESTERN
ALEUTIANS SUN NIGHT AND THEN CHANGE TO RAIN MON INTO TUE AS THE FRONT
MOVES NORTHEAST TOWARD BRISTOL BAY.

FOR SW AK...RAIN WILL SPREAD OVER THE AREA WITH SIGNIFICANT WIND. THE
KUSKOKWIM DELTA WILL HAVE BLIZZARD CONDITIONS NORTHWEST OF BETHEL
THIS MORNING UNTIL CHANGING OVER TO RAIN...WITH POSSIBLE FREEZING
RAIN DURING THE TRANSITION. PRECIPITATION WILL CHANGE BACK TO SNOW
SHOWERS TONIGHT AS THE COLD FRONT MOVES EAST. SNOW SHOWERS WILL THEN
PERSIST INTO MON BEFORE RIDGING DRIES OUT THE AREA UNTIL TUE.

SOUTH AND EAST OF THE AK RANGE...A TROPICAL MOISTURE FEED EXTENDING
FROM HAWAII WILL BRING ABUNDANT MOISTURE TO THE AREA THROUGH SUN.
RAIN...HEAVY AT TIMES...IS EXPECTED OVER COASTAL REGIONS...WITH SNOW
CHANGING TO RAIN OVER INLAND AREAS. SOME FREEZING RAIN IS POSSIBLE
OVER MUCH OF THE INTERIOR AS COLD AIR AT THE SURFACE IS SLOW TO SCOUR
OUT OF VALLEYS.  SNOW SHOWERS WILL FOLLOW THE COLD FRONT SUN NIGHT
INTO TUE BEFORE RIDGING DRIES OUT THE AREA.

.LONG TERM FORECAST...

RAIN CHANGING TO SNOW SHOWERS CAN BE EXPECTED OVER THE WEST THROUGH
MID WEEK. SNOW WILL DEVELOP OVER SW AK AND CHANGE TO SNOW SHOWERS BY
THE MIDDLE OF THE WEEK. SNOW WILL ALSO DEVELOP ALONG THE COAST SE OF
THE AK RANGE...WHILE THE INLAND ZONES REMAIN DRY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101 195
         BLIZZARD 155
MARINE...HURRICANE FORCE WIND WARNING 179 185
         STORMS 170 180
         GALES 120 125 129 130 132 150 155 160 165 172 175 176
         HEAVY FREEZING SPRAY 185
FIRE WEATHER...NONE

DS DEC 11

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
525 AM AKST SAT DEC 3 2011

AKZ121-125-031435-