Blizzard in Alaska, February 29, 2008

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM AST FRI FEB 29 2008

.ANALYSIS AND UPPER LEVELS...A CUT-OFF HIGH IS POSITIONED OVER FAR
EASTERN SIBERIA WITH HIGH AMPLITUDE TROUGH ON EITHER SIDE OF IT...ONE
EXTENDING FROM A CLOSED LOW OVER NORTHWEST CANADA SOUTHWESTWARD
ACROSS ALASKA AND THE OTHER EXTENDING FROM CHINA EASTWARD TO THE
ALEUTIANS. NORTHERLY FLOW FROM THE POLE IS ADVECTING EXTREMELY COLD
AIR SOUTHWARD ACROSS THE STATE TODAY. THE COLD ADVECTION IS RESULTING
IN GUSTY NORTHERLY WINDS...ESPECIALLY THROUGH CHANNELED AREAS OF THE
ALASKA RANGE. WINDS ARE GUSTING TO 25 TO 45 MPH ACROSS MUCH OF
INTERIOR SOUTHCENTRAL AND SOUTHWEST ALASKA AND TEMPERATURES GENERALLY
IN THE TEENS. A WEAK SURFACE LOW JUST NORTH OF MIDDLETON ISLAND
COMBINED WITH A SHORT-WAVE TROUGH OVER THE GULF ARE PRODUCING AREAS
OF SNOW FROM EASTERN PRINCE WILLIAM SOUND TO THE COPPER RIVER BASIN.
THESE FEATURES ARE HELPING TO STALL THE UPPER TROUGH OVER MAINLAND
ALASKA. OUT WEST THERE ARE MULTIPLE LOWS STRINGED ALONG A SURFACE
FRONT THAT EXTENDS FROM NEAR KAMCHATKA TO SOUTH OF THE ALEUTIANS.
A STRONG UPPER JET COMING OUT OF ASIA BETWEEN 30N AND 40N LATITUDE
CONTINUES TO DEVELOP NEW LOWS ALONG THE SOUTHERN PORTION OF THE
FRONT.

.MODEL DISCUSSION...NAM MODEL DID NOT INITIALIZE WELL WITH POSITION
AND STRENGTH OF LOWS ALONG THE FRONT OUT WEST. THE GFS/UKMET/ECMWF
WERE ALL CLOSE. ELSEWHERE...MODELS INITIALIZED WELL. THERE IS MUCH
BETTER AGREEMENT AMONG THIS MORNINGS MODEL SOLUTIONS COMPARED TO
THE LAST FEW DAYS...ESPECIALLY WITH REGARD TO THE GENERAL EVOLUTION
OF THE PATTERN IN THE SHORT-TERM. ONLY MINOR ADJUSTMENTS WILL BE
MADE TO EXISTING FORECAST.

.SHORT TERM FORECAST...GUSTY NORTHERLY WINDS WILL DEVELOP OVER
SOUTHERN PORTIONS OF SOUTHCENTRAL AND SOUTHWEST ALASKA TONIGHT AS
COLD ADVECTION CONTINUES TO PROGRESS SOUTHWARD. COMBINATION OF FRESH
SNOWFALL AND STRONG WINDS WILL RESULT IN BLIZZARD CONDITIONS THROUGH
THOMPSON PASS. COLD ADVECTION WILL NOT MAKE IT INTO THE GULF DUE TO
STALLING OF UPPER TROUGH. THE TROUGH WILL AMPLIFY SOUTHWESTWARD INTO
THE BERING...SO THAT COLD AIR WILL BE TRANSPORTED SOUTHWESTWARD
ACROSS THE PRIBILOFS AND CENTRAL BERING TONIGHT AND SATURDAY AND THEN
SOUTHWARD ACROSS THE ALEUTIANS SUNDAY. COMBINATION OF COLD
TEMPERATURES AND WINDS WILL CAUSE DANGEROUS WIND CHILLS IN THE
KUSKOKWIM VALLEY TO 45 BELOW ZERO TONIGHT THROUGH SATURDAY MORNING.
ALTHOUGH NOT AS LOW...WIND CHILLS WILL DROP BELOW ZERO FROM THE
SUSITNA VALLEY TO THE KUSKOKWIM DELTA AND PORTIONS OF BRISTOL BAY. AS
THE WIND MOVES INTO THE PRIBILOFS EXPECT VISIBILITIES TO BE REDUCED
IN BLOWING SNOW WITH SOME FRESH SNOW SITTING ON THE GROUND FROM
TUESDAY. THE SEA ICE HAS REACHED SAINT PAUL BUT THERE IS STILL SOME
OPEN WATER EAST TO NORTHEAST OF SAINT GEORGE...SO THERE IS THE
POTENTIAL FOR SNOW SHOWERS AS THE COLD AIR MOVES ACROSS THE OPEN
WATER. AS THE UPPER TROUGH CONTINUES TO AMPLIFY ON SATURDAY AN UPPER
LOW WILL DEVELOP OVER THE EASTERN BERING AND MOVE ACROSS THE
PRIBILOFS. THIS LOOKS LIKE IT WILL PRODUCE SNOWFALL ACROSS THE
PRIBILOFS STARTING SATURDAY AFTERNOON AND CONTINUING THROUGH THE
EVENING. A BLIZZARD WATCH HAS BEEN ISSUED FOR THIS TIME PERIOD.

AS THE MAINLAND TROUGH AMPLIFIES ACROSS THE BERING SEA STORMS FORMING
OVER THE NORTH PACIFIC WILL BE PULLED NORTHEASTWARD TOWARD THE
MAINLAND. UPPER LEVEL FLOW WILL QUICKLY SHIFT TO THE SOUTH OVER THE
WEEKEND...BRINGING A QUICK END TO THE VERY COLD AND WINDY CONDITIONS.
AS THE INITIAL SHIFT OCCURS SATURDAY THE MOISTURE OVER THE NORTHERN
GULF WILL BE PUSHED INLAND...SO THERE IS A CHANCE OF SOME LIGHT SNOW
ACCUMULATION OVER SOUTHERN PORTIONS OF SOUTHCENTRAL
SATURDAY...INCLUDING ANCHORAGE AND VICINITY. MULTIPLE LOWS WILL
TRACK TOWARD THE ALASKA PENINSULA SATURDAY AND PUSH A FRONT ACROSS
THE GULF WHICH WILL THEN WEAKEN AS IT PUSHES INLAND SATURDAY NIGHT.
THIS INITIAL WARM PUSH WILL RAISE TEMPERATURES BACK TO NEAR
NORMAL...ESPECIALLY ALONG THE COAST. A MORE SIGNIFICANT WARM-UP IS
IN STORE MONDAY FOR MAINLAND ALASKA THROUGH TUESDAY AS DEEP LOW
MOVES INTO THE BERING SEA.

.LONG TERM FORECAST...A HIGH AMPLITUDE TROUGH OVER THE BERING AND
RIDGE OVER THE EAST PACIFIC WILL RESULT IN AN ACTIVE STORM TRACK FROM
THE PACIFIC NORTHWARD TOWARD MAINLAND ALASKA WHICH WILL KEEP MOST
PLACES AT OR ABOVE NORMAL TEMPERATURES WITH A CHANCE OF PRECIPITATION
EVERY FEW DAYS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING ZONE 131 THOMPSON PASS.
         BLIZZARD WATCH ZONE 195.
MARINE...GALE WARNING 130 150 155 170 176 179 180 185.
         HEAVY FREEZING SPRAY WARNING 130 140 141 165 179 185.
FIRE WEATHER...NONE.

SEB FEB 08