Blizzard in Alaska, November 5, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
504 AM AKDT SAT NOV 5 2011

.ANALYSIS AND UPPER LEVELS...

TRANSITORY UPPER RIDGE STRETCHES NORTH FROM THE NORTH PACIFIC OVER
BRISTOL BAY AND SOUTHWEST ALASKA. A CLOSED UPPER LEVEL LOW IN THE
BERING SEA IS SUPPORTING A GALE FORCE FRONT THAT STRETCHES SOUTH FROM
NEAR THE PRIBILOFS ACROSS THE CENTRAL ALEUTIANS. CYCLOGENESIS IS
UNDERWAY WITH LOW PRESSURE JUST NORTH AND WEST OF SAINT PAUL
CURRENTLY AND THIS LOW WILL MOVE EAST TO THE KUSKOKWIM DELTA
TONIGHT...WITH SECONDARY LOW DEVELOPMENT OVER THE NORTHWEST GULF THAT
WILL MOVE INLAND OVER NORTHEAST PRINCE WILLIAM SOUND SUNDAY MORNING.
THE MAIN LOW NOW APPEARS IT TOO WILL HANG TOGETHER AND REACH THE
WESTERN AND NORTHERN GULF SUNDAY NIGHT INTO THE EARLY PART OF NEXT
WEEK. A SMALL LOW WILL MOVE SOUTH OF THE ALEUTIAN ISLANDS SUNDAY AND
MONDAY AND BRING RAIN AND GALE FORCE WINDS MAINLY TO THE CENTRAL AND
EASTERN ALEUTIANS. FINALLY...A STRONG LOW WITH CENTRAL PRESSURE ABOUT
965 MILLIBARS LOW WILL MOVE FROM THE NORTHWEST PACIFIC MON NIGHT
THROUGH THE BERING SEA WHILE DEEPENING INTO THE 940S MILLIBARS AS IT
APPROACHES THE SEWARD PENINSULA. THIS SYSTEM HAS THE POTENTIAL TO BE
A SIGNIFICANT WEATHER MAKER.

.MODEL DISCUSSION...

MODEL SOLUTIONS ARE PRETTY CLOSE THROUGH EARLY WEEK...THOUGH THE
EUROPEAN AND NAM MODELS WERE A BIT MORE PREFERRED OVER THE GFS DUE TO
RESOLUTION AND CONSISTENCY ISSUES. EARLY NEXT WEEK...THE GFS IS
CONSISTENTLY FARTHER SOUTH AND EAST WITH THE STRONG LOW IN THE BERING
SEA EARLY NEXT WEEK...BUT OVERALL GLOBAL AND GLOBAL ENSEMBLE MODEL
SOLUTIONS ARE COMING CLOSER TOGETHER WITH EACH SUCCESSIVE RUN AS WE
GET CLOSER TO THE EVENT.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

LAST OF SHORTWAVE DISTURBANCES IS CURRENTLY MOVING OVER SOUTHCENTRAL
ALASKA...WITH CLEARING COMMENCING OVER THE NEXT FEW HOURS FROM WEST
TO EAST TODAY AS THE UPPER RIDGE OVER SOUTHWEST ALASKA QUICKLY MOVES
THROUGH. THE BLIZZARD WARNING FOR THOMPSON PASS WILL REMAIN AS
PRESSURE GRADIENT TIGHTENS WITH WEAK LOW OVER THE NORTHEAST GULF
THIS MORNING.

ATTENTION TURNS TO THE APPROACHING SYSTEM FROM THE WEST THAT WILL
MOVE INTO THE REGION TODAY AND BRING RAIN TO KODIAK...ALL SNOW NORTH
OF KACHEMAK BAY...WITH A SNOW/RAIN MIX NEAR KACHEMAK BAY. LONGWAVE
TROUGH BECOMES STATIONARY JUST WEST OF THE ALASKA/ALEUTIAN RANGES
FROM SATURDAY NIGHT THROUGH EARLY TUESDAY WITH SEVERAL DISTURBANCES
OF VARYING STRENGTH MOVING THROUGH. THIS WILL MEAN PERIODS OF LIGHT
SNOW FOR MOST OF SOUTHCENTRAL MAINLAND FROM SATURDAY NIGHT THROUGH AT
LEAST MONDAY AFTERNOON...WITH HEAVIER AMOUNTS ALONG SOUTHWEST FACING
SLOPES OF THE MOUNTAIN RANGES. WILL GENERALLY STICK WITH 1 TO 3
INCHES ACCUMULATION FOR TONIGHT INTO SUNDAY...WITH ADDITIONAL
ACCUMULATIONS THROUGH AT LEAST MONDAY MIDDAY...WITH HEAVIER AMOUNTS
TOWARDS VALDEZ AND THOMPSON PASS.

SOUTHWEST ALASKA...

BLIZZARD CONDITIONS WILL DEVELOP THIS MORNING OVER THE KUSKOKWIM
DELTA AS SNOW DEVELOPS AHEAD OF A DEVELOPING LOW PRESSURE SYSTEM OVER
THE BERING. EXPECT ALL SNOW OVER SOUTHWEST ALASKA FOR MOST OF THE
WEEKEND WITH THIS EVENT EXCEPT FOR A RAIN/SNOW MIX NEAR KING SALMON
WITH ALL RAIN TO THE SOUTH ALONG THE AKPEN. AS THE LOW MAKES LANDFALL
NEAR THE MOUTH OF THE KUSKOKWIM RIVER TONIGHT AND THEN MOVES INLAND
SUNDAY...EXPECT STRONG GALE FORCE WINDS WITH ISOLATED STORM FORCE
GUSTS ON THE BACK SIDE OF THE LOW ALONG THE COASTLINE AND OUT OVER
THE EASTERN BERING WATERS.

BERING SEA/ALEUTIANS...

LOW PRESSURE SYSTEM AND FRONTAL BOUNDARY IN THE BERING MOVE EAST
ACROSS THE REGION TOWARDS THE GULF THROUGH EARLY SUNDAY WITH GALE
FORCE WINDS AND ISOLATED STORM FORCE GUSTS ON THE IMMEDIATE BACK SIDE
OF THE LOW OVER THE EASTERN BERING AND BRISTOL BAY REGIONS. NEXT
SYSTEM COMES IN THE WAY OF A SMALL LOW WHICH WILL REMAIN JUST SOUTH
OF THE ALEUTIAN CHAIN AS IT MOVES EAST. TEMPERATURES SHOULD STAY WARM
ENOUGH FOR ALL RAIN ALONG WITH GALE FORCE WINDS. HOWEVER...A BRIEF
PERIOD OF SNOW OR A FEW SNOW SHOWERS MAY BE POSSIBLE ON THE PERIPHERY
ON THE LEADING EDGE AND ON THE BACK SIDE OF THIS SYSTEM.

.LONG TERM FORECAST...

ATTENTION WILL BE FOCUSED ON THE POTENTIAL FOR A MAJOR LOW PRESSURE
SYSTEM TO MOVE ACROSS THE WESTERN ALEUTIANS FROM THE NORTHWEST
PACIFIC OCEAN MONDAY NIGHT AND APPROACH THE SEWARD PENINSULA TOWARDS
MIDWEEK. AS THE STORM FORCE LOW WILL BE INTENSIFYING AS IT CROSSES
THE BERING IT WILL LIKELY BE ABLE TO PRODUCE A LARGE SOUTHWESTERLY
SWELL. WILL CONTINUE TO MONITOR FOR HIGH SURF AND COASTAL FLOODING
POTENTIAL AS THE EVENT DRAWS NEAR. FOR SOUTHCENTRAL...MODELS INSIST
ON DEVELOPING ANOTHER SECONDARY LOW AS THE FRONT ASSOCIATED WITH THIS
SYSTEM ENTERS THE GULF ON WEDNESDAY...WHICH WOULD INCREASE THE SNOW
POTENTIAL FOR MIDWEEK OVER A LARGE PART OF SOUTHCENTRAL ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131 155.
MARINE...GALES...130 132 138 150 155 160 165 170 172 175 176 179 180
185
         STORMS...
FIRE WEATHER...NONE.

29 NOV 11