Blizzard in Alaska, March 30 to 31, 2010

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
635 AM AKDT TUE MAR 30 2010

.ANALYSIS AND UPPER LEVELS...
TWO BROAD UPPER LEVEL TROUGHS DOMINATE THE FAR NORTHERN PACIFIC THIS
MORNING...WITH ONE TROUGH ENTERING THE WESTERN BERING SEA AND ANOTHER
STRETCHED OUT ACROSS THE STATE AND THE GULF OF ALASKA. THE LATTER
TROUGH FEATURES A CUTOFF LOW OVER THE GULF WHILE A SECOND UPPER LEVEL
LOW RESIDES FURTHER WEST OVER EASTERN RUSSIA. AN UPPER LEVEL RIDGE IS
DEVELOPING OVER THE NORTH CENTRAL PACIFIC SOUTH OF THE CENTRAL
ALEUTIANS...HELPING TO NUDGE THE 180 KT POLAR JET NORTH TOWARDS THE
ISLAND CHAIN.

AT THE SURFACE...A FILLING 971 MB LOW PRESSURE CENTER IN THE CENTRAL
GULF IS HELPING TO FUEL SOME SCATTERED SHOWERS OVER THE NORTHERN
GULF...BUT ONLY A FEW OF THESE ARE AFFECTING THE COAST. UNSEASONABLY
COLD TEMPERATURES AND STRONG NORTHWESTERLY WINDS CONTINUE TO PLAGUE
THE WEST COAST OF THE STATE AND THE EASTERN BERING SEA. LIGHT SNOW
HAS DEVELOPED OVER SOUTHWESTERN ALASKA AS A MID LEVEL DISTURBANCE
PUSHES EAST OFF THE BERING. A STRONG LOW 800 MILES SOUTHWEST OF
SHEMYA IS QUICKLY TRACKING NORTHEASTWARD AND IS ON A COLLISION COURSE
WITH THE CENTRAL ALEUTIANS TOMORROW AFTERNOON.

.MODEL DISCUSSION...
NOT MUCH DISCREPANCY IN THE MODELS THIS MORNING...WITH ALL SOLUTIONS
IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD. IN THE GULF...THE
ECMWF AND THE NAM INITIALIZED THE BEST WITH REGARDS TO THE CENTER OF
THE CURRENT LOW AND THE ASSOCIATED SHORTWAVE LIFTING NORTH ACROSS THE
EASTERN GULF. THE HIGHER RESOLUTION NAM ALSO DID A BETTER JOB IN
DEPICTING THE ELONGATED SHAPE OF THE LOW DUE TO THE INTERACTION AND
EVENTUAL ABSORPTION OF A WEAKER LOW A FEW HOURS AGO. OUT WEST...THE
MODELS ARE ACCELERATING THE STORM FORCE LOW THAT WILL AFFECT THE
ALEUTIANS MIDWEEK. THE NAM IS CURRENTLY SLOWER THAN THE GFS AND
ECMWF...WITH THE GFS SOLUTION ALSO SLIGHTLY FARTHER SOUTH THAN THE
ECMWF.

.SHORT TERM FORECAST...
.SOUTHCENTRAL ALASKA...THE LOW IN THE GULF WILL CONTINUE TO WEAKEN
BEFORE DISSIPATING TONIGHT. SCATTERED SHOWERS WILL LINGER ALONG THE
GULF COAST AND COOK INLET TODAY AS THE LOW WINDS DOWN. STRONG
NORTHWESTERLY WINDS BEHIND THIS LOW WILL CONTINUE TO AFFECT KODIAK
ISLAND TODAY WITH SNOW THIS MORNING AS A BAND ROTATES AROUND THE GULF
LOW. AN UPPER LEVEL TROUGH CURRENTLY OVER SOUTHWEST ALASKA WILL LIFT
NORTHEAST TONIGHT ACROSS THE COOK INLET REGION. THOUGH NOT AS
IMPRESSIVE LOOKING AS IT WAS FOR THE LAST COUPLE OF DAYS...IT IS
STILL EXPECTED THAT THE TROUGH SHOULD PROVIDE ENOUGH LIFT IN
SOUTHERLY FLOW FOR THE ANCHORAGE BOWL TO SEE A BRIEF PERIOD OF LIGHT
SNOW THIS EVENING. THE SUSITNA VALLEY SHOULD SEE SLIGHTLY MORE
SIGNIFICANT SNOW...UP TO 2 INCHES...AS THE STRONGER ENERGY ALOFT IS
LOCATED FARTHER NORTH. THE FOCUS SHIFTS TO KODIAK ISLAND ON WED AS A
FRONT AHEAD OF AN INTENSE LOW CURRENTLY MOVING TOWARDS THE ALEUTIANS
MAKES ITS WAY NORTH AND EAST INTO THE GULF OF ALASKA. PRECIP SHOULD
START AS SNOW ON KODIAK ISLAND BEFORE MIXING WITH RAIN WED EVENING AS
THE WARM FRONT MOVES THROUGH. THIS FRONT MAKES ITS WAY TOWARDS THE
NORTH GULF COAST WED NIGHT INTO THU SPREADING A MIX OF RAIN AND
SNOW TO THE COAST AND USUAL UPSLOPE AREAS. DOWNSLOPING SHOULD KEEP
THE ANCHORAGE BOWL AND MAT-SU REGION DRY.

.SOUTHWEST ALASKA...LIGHT SNOW WILL FALL OVER THE KUSKOKWIM VALLEY
AND BRISTOL BAY REGIONS TODAY AHEAD OF A POTENT UPPER LEVEL TROUGH.
THE KUSKOKWIM DELTA SHOULD SEE SOME SUN THIS AFTERNOON AS SKIES CLEAR
BEHIND THE UPPER TROUGH. SKIES SHOULD CLEAR FURTHER INLAND AND AROUND
BRISTOL BAY TONIGHT AS THE SHORTWAVE TROUGH CONTINUES TO MOVE
EASTWARD BEFORE CLOUDS MOVE IN AGAIN AHEAD OF THE STORM SYSTEM IN THE
ALEUTIANS. THIS STORM WILL START TO AFFECT THE ALASKA PENINSULA THIS
EVENING WITH BLIZZARD CONDITIONS POSSIBLE AFTER MIDNIGHT AHEAD OF THE
WARM FRONT. AS THE FRONT PASSES...LOCATIONS ON THE AKPEN SHOULD SEE A
PERIOD OF CHANGEOVER TO RAIN BEFORE CONDITIONS DETERIORATE AS SNOW
RETURNS BEHIND THE LOW WED NIGHT. SNOW WILL SPREAD INTO MAINLAND
SOUTHWEST ALASKA WED NIGHT INTO THU AS AN INVERTED TROUGH ROTATES
AROUND THE MAIN LOW. EXPECT GUSTY WINDS AND WIDESPREAD SNOW SHOWERS
ACROSS THE AKPEN ON THU IN THE COLD ADVECTION IN THE WAKE OF THE
STORM SYSTEM.

.ALEUTIANS AND BERING SEA...THE MAJOR STORM SYSTEM WINDING UP
SOUTHWEST OF THE ALEUTIANS WILL RAPIDLY MOVE NORTHEAST TOWARDS THE
CENTRAL ALEUTIANS. SNOW SHOULD START IN THE CENTRAL ALEUTIANS THIS
AFTERNOON AHEAD OF THE WARM FRONT. THIS COMBINED WITH EXPECTED STORM
FORCE WINDS HAS NECESSITATED A BLIZZARD WARNING FOR THE CENTRAL
ALEUTIANS. SNOW MAY MIX WITH RAIN AND POSSIBLY CHANGE ALL THE WAY
OVER TO RAIN FOR A BRIEF PERIOD...PARTICULARLY AROUND ATKA...BEFORE
COLD ADVECTION BEHIND THE LOW KICKS IN AND BLIZZARD CONDITIONS
RESUME. CURRENTLY THINKING THAT GIVEN THE SPEED OF THE LOW AND THE
AMOUNT OF WARM ADVECTION ALONG WITH THE RELATIVELY WARMER AIRMASS IN
PLACE...THE EASTERN ALEUTIANS INCLUDING UNALASKA SHOULD ESCAPE
BLIZZARD CONDITIONS. THEY MAY SEE A BRIEF PERIOD OF SNOW AND BLOWING
SNOW THIS EVENING BEFORE SNOW CHANGES OVER TO RAIN AROUND MIDNIGHT.
NOT SO FOR THE PRIBILOFS THOUGH AS THEY ARE DEEP ENOUGH IN THE COLD
AIR THAT PRECIP SHOULD STAY ALL SNOW WITH BLIZZARD CONDITIONS
EXPECTED TO BEGIN AFTER MIDNIGHT TONIGHT AND CONTINUE THROUGH WED
AFTERNOON.

.LONG TERM FORECAST...
THE ALEUTIAN STORM PROGRESSES INTO THE GULF OF ALASKA BY THU EVENING.
THE STORM WILL GRADUALLY WEAKEN IN THE GULF AS IT STALLS OUT UPSTREAM
OF A RIDGE CENTERED OVER THE YUKON/NORTHWEST TERRITORIES. A SERIES OF
SHORTWAVES ROTATING AROUND THIS REMNANT LOW WILL ALLOW FOR SHOWERS TO
CONTINUE ACROSS MUCH OF THE GULF COAST INTO THE WEEKEND WITH
SEASONABLE TEMPERATURES. ONCE AGAIN...DOWNSLOPING SHOULD KEEP THE
ANCHORAGE BOWL AND MAT-SU REGION DRY THROUGH THE WEEKEND.

IN THE WEST...SNOW SHOWERS AND BREEZY NORTHWEST WINDS WILL BE IN
PLACE ACROSS THE BERING BY THU IN THE WAKE OF THE LOW. A SERIES OF
UPPER LEVEL DISTURBANCES MOVING ACROSS THE BERING SHOULD ENHANCE
SNOWFALL ACROSS THE ALEUTIANS AND AKPEN AT TIMES DURING THE LATTER
HALF OF THE WEEK. ANOTHER SIGNIFICANT LOW PRESSURE SYSTEM MOVES INTO
THE WESTERN ALEUTIANS ON FRI AND THROUGH THE REST OF THE CHAIN TO THE
AKPEN OVER THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...187 195.
         BLIZZARD WATCH...181.
MARINE...STORM WARNING...170 172.
         GALE WARNING...130 132 138 150 155 160 165 171 175 176 179.
         HEAVY FREEZING SPRAY WARNING...150 155 160 165.
FIRE WEATHER...NONE.

KS/WOOD MAR 10