Blizzard in Alaska, March 23 to 24, 2009

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
125 PM AKDT MON MAR 23 2009

.ANALYSIS AND UPPER LEVELS...A LARGE UPPER LOW IS NEARLY STATIONARY
OVER THE EASTERN BERING SEA. A TROUGH EXTENDING SOUTHEASTWARD FROM
THIS LOW IS LIFTING NORTHWARD TOWARD THE GULF. A STRONG WESTERLY JET
IS VERY EVIDENT IN SATELLITE IMAGERY...WITH A SHORT-WAVE EMBEDDED
WITHIN THE TROUGH SHOOTING EASTWARD TOWARD BRITISH COLUMBIA. ALSO
EVIDENT IN WATER VAPOR IMAGERY IS ABUNDANT MOISTURE AHEAD OF THE
TROUGH ROTATING NORTHWESTWARD ACROSS THE SOUTHERN MAINLAND. AT THE
SURFACE...A MODERATE LOW IS CENTERED OVER THE WESTERN GULF AS SEEN
IN A 7 AM QUIKSCAT IMAGE. THIS POSITION IS A LITTLE FARTHER WEST
THAN ANY OF THE MODELS INDICATED FOR THAT TIME...SO THIS MAY LEND
CREDENCE TO THE FARTHER WEST NAM FORECAST. OFFSHORE FLOW OVER
SOUTHCENTRAL IS KEEPING ALL BUT THE IMMEDIATE COAST DRY. STEADY
PRECIP AHEAD OF THE TROUGH EXTENDS FROM THE SURFACE LOW ACROSS
KODIAK ISLAND TO BRISTOL BAY AND ON UP TO THE KUSKOKWIM DELTA.
COLD ADVECTION BEHIND THE UPPER TROUGH IS MOVING ACROSS THE ALASKA
PENINSULA TO SOUTHERN KODIAK ISLAND...PRODUCING STRONG WINDS AND
BLOWING SNOW. SINCE WINDS ARE EXPECTED TO INCREASE FURTHER THIS
AFTERNOON AND EVENING HAVE ISSUED A BLIZZARD WARNING FOR KODIAK
ISLAND FROM 4 PM THIS AFTERNOON TO 5 AM TUESDAY. OUT OVER THE BERING
SEA AND ALEUTIANS...COLD ADVECTION SNOW SHOWERS CONTINUE.

REDOUBT VOLCANO...REDOUBT VOLCANO ERUPTED MULTIPLE TIMES LAST NIGHT
WITH THE LAST MAJOR ERUPTION OCCURRING AROUND 430 AM. ASHFALL IS
STILL BEING REPORTED ACROSS THE WESTERN SUSITNA VALLEY AND ALONG
THE ALASKA RANGE. ASHFALL ADVISORIES HAVE BEEN EXTENDED UNTIL 4 PM
FOR ZONE 145 AND 151. BARRING ANY ADDITIONAL ERUPTIONS THIS
AFTERNOON EXPECT ASHFALL TO DISSIPATE THROUGH THE AFTERNOON AND
ADVISORIES SHOULD BE ALLOWED TO EXPIRE AT 4 PM.

.MODEL DISCUSSION...OTHER THAN MODEL DIFFERENCES AND ERROR IN
POSITION OF GULF LOW...MODELS ARE IN VERY GOOD AGREEMENT THROUGH
THE END OF THE WEEK. BASED ON THE QUIKSCAT IMAGE MENTIONED ABOVE
PLAN ON LEANING TOWARD THE NAM POSITION WITH THE LOW IN THE GULF.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...SOME LIGHT SNOW WILL MOVE ONSHORE ALONG THE
NORTHERN GULF COAST TONIGHT AS THE GULF LOW DRIFTS NORTHWARD. KODIAK
ISLAND AND VICINITY WILL SEE THE GREATEST IMPACT FROM THIS SYSTEM
AS COLD AIR MOVING IN FROM THE WEST AIDS IN INCREASING WINDS. AS
THE LOW GETS TO ITS CLOSEST POINT TO THE ISLAND THIS EVENING THE
PRESSURE GRADIENT WILL ALSO INCREASE SIGNIFICANTLY AND CONTRIBUTE
TO WINDS. COMBINED WITH STEADY SNOW EXPECT WIDESPREAD BLIZZARD
CONDITIONS TO LAST THROUGH MOST OF THE NIGHT. AN UPPER LOW WILL
FORM OVER THE CENTRAL GULF TONIGHT AND BE DRIVEN EASTWARD BY THE
WESTERLY JET. THIS WILL HELP PULL THE LOW EASTWARD LATE TONIGHT
AND TUESDAY. MEANWHILE A SHORT-WAVE MOVING AROUND THE BACK SIDE
OF THE UPPER LOW OVER THE EASTERN BERING...HELPING TO PUSH IT
SOUTHWESTWARD ACROSS THE SOUTHERN BERING. THUS...WITH ENERGY IN
THE GULF PUSHING EAST AND ENERGY IN THE BERING PUSHING WEST THE
UPPER TROUGH WILL WEAKEN SIGNIFICANTLY AS IT PUSHES NORTHWARD
ACROSS SOUTHCENTRAL TUESDAY AND TUESDAY NIGHT. EXPECT NOTHING MORE
THAN A FEW SHOWERS TO ACCOMPANY THE TROUGH. THE UPPER TROUGH WILL
BE RE-CENTERED FURTHER WEST OVER THE BERING...SO THE NEXT MAJOR LOW
WILL TRACK QUICKLY FROM THE NORTH PACIFIC TUESDAY TO THE GULF
THURSDAY NIGHT. IMPACTS OF WIND AND PRECIPITATION WILL BE WIDESPREAD
BEGINNING TUESDAY NIGHT AND LASTING THROUGH THE END OF THE WEEK.

SOUTHWEST ALASKA...THE BAND OF SNOW OVER SOUTHWEST ALASKA IS PUSHING
SOUTHWESTWARD AS THE UPPER TROUGH FROM BRISTOL BAY TO THE GULF MOVES
NORTHWARD CAUSING FLOW TO BECOME MORE EASTERLY...AND AS A SHORT-WAVE
DROPS DOWN THE WEST SIDE OF THE UPPER LOW WITH A GOOD PUSH OF
NORTHERLY FLOW BEHIND IT. THESE DIVERGENT MOTIONS WILL CAUSE THE
BAND TO GRADUALLY DISSIPATE TONIGHT. THE NEXT SYSTEM WILL TRACK
SOUTH AND EAST OF THE ALASKA PENINSULA...BUT DUE TO LARGE SIZE AND
INTENSITY OF SYSTEM EXPECT WIDESPREAD IMPACTS MID TO LATE WEEK.

BERING SEA/ALEUTIANS...THE NEXT SYSTEM WILL PASS JUST SOUTH OF THE
EASTERN ALEUTIANS AND ALASKA PENINSULA TUESDAY THROUGH
WEDNESDAY...BRINGING LOTS OF STEADY PRECIPITATION AND STRONG WINDS
ON THE BACK SIDE OF THE LOW. THIS IS A GOOD TRACK FOR BLIZZARD
CONDITIONS IN THESE AREAS...DEPENDING ON HOW FAR NORTH THE FRONTAL
SYSTEM PUSHES. AT THIS POINT IT LOOKS LIKE THE WARM FRONT WILL MAKE
IT UP TO MOST OF THE ALASKA PENINSULA...RESULTING IN WARMER
TEMPERATURES AND POSSIBLY SOME RAIN. THE EASTERN ALEUTIANS WILL STAY
SAFELY ON THE COLD SIDE OF THE FRONT...BUT MAY NOT SEE STEADY SNOW.
SO...AT THIS POINT PLAN ON JUST CARRYING SNOW AND BLOWING SNOW FOR
THE EASTERN ALEUTIANS AND WILL RE-EVALUATE THE BLIZZARD POTENTIAL AS
WE GET CLOSER TO THE EVENT. ONCE THE SYSTEM MOVES BY WILL RETURN TO
COLD ADVECTION SNOW SHOWERS AND GUSTY WINDS THROUGH THE END OF THE
WEEK AS THIS COLD PATTERN REMAINS IN PLACE.

.LONG TERM FORECAST...LONG-WAVE PATTERN LOOKS TO REMAIN IN PLACE
THROUGH THE EXTENDED PERIOD...MAINTAINING GENERALLY BELOW NORMAL
TEMPERATURES ACROSS THE ALASKA REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...120 130 132 138 140 150 155 170 172 179.
         HEAVY FREEZING SPRAY...150 155 165 179.
FIRE WEATHER...NONE.

SEB MAR 09