Blizzard and High Wind in Alaska, December 10 to 12, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST FRI DEC 9 2011

.ANALYSIS AND UPPER LEVELS...THE LARGE UPPER LEVEL TROUGH REMAINS IN
THE WESTERN BERING SEA WITH AN UPPER LEVEL RIDGE OVER THE WEST COAST
OF NORTH AMERICA. A CHANGE FROM THE PAST FEW DAYS IS THERE IS AN
UPPER LEVEL SHORT WAVE MOVING ACROSS THE MAINLAND PART OF THE STATE
WHICH HAS FLATTENED THE TOP OF THE RIDGE AND TURNED UPPER LEVEL FLOW
MORE ZONAL OVER THE STATE. THE JET STREAM REMAINS FROM THE SOUTHWEST
OVER THE ALEUTIANS AS ANOTHER UPPER LEVEL RIDGE IS DEVELOPING JUST
EAST OF THE JET. THIS NEW RIDGE WILL AMPLIFY QUICKLY AND MOVE TO THE
ALCAN BORDER BY SATURDAY NIGHT BRINGING THE JET STREAM BACK OVER THE
GULF OF ALASKA AND SOUTH CENTRAL ALASKA.
THE LARGE AND STRENGTHENING SURFACE LOW IN THE FAR WESTERN BERING SEA
WILL FOLLOW THE SAME BASIC TRACK AS THE PREVIOUS LOW. THE FRONT
ASSOCIATED WITH THIS LOW IS MOVING QUICKLY ACROSS THE BERING SEA AND
WILL BE THE BIG WEATHER MAKER FOR THE ALEUTIAN ISLANDS AND SOUTHWEST
ALASKA THROUGH TOMORROW.

.MODEL DISCUSSION...MODELS ARE DOING WELL WITH THE BIG DISCREPANCY
BETWEEN THEM BEING THE DEVELOPMENT OF A LOW SATURDAY NIGHT ALONG THE
STRONG FRONT THAT WILL BE IN THE WESTERN GULF OF ALASKA. WHILE THE
ECMWF SOLUTION HAS COME MORE IN LINE WITH THE GFS/NAM SOLUTION THAT
WAS PREFERRED WITH THIS FEATURE YESTERDAY THE ECMWF STILL DEVELOPS
THE LOW WELL SOUTH OF THE GULF AND THEN RAPIDLY MOVES IT NEAR KODIAK
ISLAND. THE GFS AND NAM STILL SHOW THE MAIN LOW DEVELOPING NORTHEAST
OF KODIAK ISLAND WHICH IS A MORE REASONABLE SOLUTION. THEREFORE THE
NAM AND GFS ARE PREFERRED WITH THIS SYSTEM.

.SHORT TERM FORECAST...THE SHORT WAVE MOVING ACROSS THE INTERIOR AND
SOUTH CENTRAL ALASKA HAS BEEN BRINGING SNOW SHOWERS AND THEN AREAS OF
FOG BEHIND THEM. THIS WILL CONTINUE TO PUSH EASTWARD OVERNIGHT. THERE
WILL BE A TRIPLE POINT LOW DEVELOPING NORTHEAST OF KODIAK ISLAND LATE
SATURDAY NIGHT WHICH WILL HAVE A LARGE IMPACT ON THE WEATHER IN SOUTH
CENTRAL ALASKA AND ALONG THE GULF COAST. BEFORE THIS TRIPLE POINT LOW
DEVELOPS THE FRONT WILL PUMP A LOT OF MOISTURE INTO THE SUSITNA
VALLEY RESULTING IN A WINTER WEATHER WATCH FOR HEAVY SNOW. THERE IS
ALSO A HIGH WIND WATCH FOR TURNAGAIN ARM AND HIGHER ELEVATIONS IN THE
ANCHORAGE AREA FOR SATURDAY NIGHT. WHEN THIS LOW DEVELOPS NORTHEAST
OF KODIAK IT WILL DIVERT THE MOISTURE AND PRESSURE GRADIENT FARTHER
EAST AND END THESE THREATS. HOWEVER THE TIGHTENING PRESSURE GRADIENT
WILL BRING A CHANCE OF BLIZZARD CONDITIONS IN BOTH THE EASTERN KENAI
PENINSULA AS WELL AS THROUGH THOMPSON PASS.

SOUTHWEST AND BERING SEA...THE STORM IN THE BERING SEA ALONG WITH ITS
WEATHER FRONT ARE BRINGING GALE AND STORM FORCE WINDS TO MOST OF THE
BERING SEA REGION. STRONGEST WINDS WILL BE ALONG THE FRONT AS IT
MOVES ACROSS THE EASTERN BERING SEA THIS EVENING AND REACHES
SOUTHWEST ALASKA TOMORROW MORNING. PRECIPITATION WILL BE ALL RAIN
ALONG THE ALASKA PENINSULA AND EASTERN ALEUTIANS. THE BIG QUESTION OF
PRECIPITATION TYPE WILL BE IN THE BRISTOL BAY REGION AND KUSKOKWIM
DELTA. THE ORIENTATION OF THE FRONT AS WELL AS THE AMOUNT OF WARM AIR
MOVING IN WITH IT MAKES IT LIKELY THAT THERE WILL BE RAIN MIXING IN
WITH THE SNOW...OR PERHAPS EVEN MOSTLY RAIN FALLING. EVEN AS ONE GETS
INLAND THERE LOOKS TO BE ENOUGH WARM AIR TO MIX IN RAIN WHERE THE
STRONGEST WINDS ARE WITH SNOW BEING IN THE LESS WINDY AREAS.
THEREFORE BLIZZARD CONDITIONS ARE NOT EXPECTED BUT THERE IS THE
CHANCE OF THEM DEVELOPING SO THIS SITUATION SHOULD STILL BE
MONITORED.

.LONG TERM FORECAST...THE LONG WAVE PATTERN STILL IS NOT EXPECTED TO
CHANGE A LOT THROUGH THE MIDDLE OF NEXT WEEK. THE DOMINANT UPPER
LEVEL LOW WILL REMAIN OVER THE WESTERN BERING SEA WITH A LARGE UPPER
LEVEL RIDGE OVER THE WEST COAST OF NORTH AMERICA. THE MAIN STORM
TRACK WILL SEND A SERIES OF STRONG LOWS THROUGH THE NORTHWEST BERING
SEA. THE PERSISTENT JET STREAM FROM THE SOUTHWEST OVER MAINLAND
SOUTHERN ALASKA WILL HELP TO DEVELOP SECONDARY LOWS ALONG THE FRONTS
THAT ARE PRODUCED BY THE BERING SEA LOWS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 125 131.
         HIGH WIND WATCH 101.
         HEAVY SNOW WATCH 145.
MARINE...GALE 125 130 138 140 141 165 171.
         STORM 120 132 150 155 160 170 172 175 176 179 180 185.
FIRE WEATHER...NONE.

DEC 11