Blizzard in Alaska, March 14, 2010

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1220 PM AKST SAT MAR 13 2010

.ANALYSIS AND UPPER LEVELS...A HIGH AMPLITUDE TROUGH IS CENTERED
OVER THE EASTERN BERING AND WESTERN ALASKA EXTENDING ALL THE WAY
DOWN TOWARD THE TROPICS. A DEEP LOW EMBEDDED WITHIN THIS TROUGH
APPROXIMATELY 350 NM SOUTH OF KODIAK ISLAND HAS BECOME VERTICALLY
STACKED AND STARTED TO WEAKEN WHILE ITS EASTWARD PROGRESSION HAS
SLOWED TO A HALT. THE FRONTAL SYSTEM...LED BY THE TRIPLE POINT IS
MOVING NORTHWARD INTO THE SOUTHERN GULF. STEADY SNOW HAS DEVELOPED
ON KODIAK ISLAND OUT AHEAD OF THE FRONT AND IS COMBINING WITH
STRONG NORTHEAST WINDS TO PRODUCE LOW VISIBILITIES. THE BLIZZARD
WATCH FOR KODIAK WAS CANCELLED THIS MORNING SINCE THE DEEP MOISTURE
ALONG THE FRONT WILL STAY OFFSHORE. HOWEVER...THERE MAY BE VERY
BRIEF PERIODS OF NEAR ZERO VISIBILITY WHEN THE SNOW INTENSITY
PICKS UP A BIT. COLD ADVECTION DOWN THE BACK SIDE OF THE STORM
IS PRODUCING WIDESPREAD SNOW SHOWERS OVER THE
BERING...ALEUTIANS...AND SOUTHERN ALASKA PENINSULA WITH BLIZZARD
CONDITIONS BEING OBSERVED ALONG PORTIONS OF THE ALASKA PENINSULA.
EXPECT SHOWERS WILL BECOME LESS STEADY LATER TODAY AS THE STORM
PULLS A LITTLE FURTHER EAST SO THAT VISIBILITIES WILL JUMP UP
AND DOWN INSTEAD OF THE PERSISTENT ONGOING LOW VISIBILITIES.

OUT OVER THE WESTERN BERING A RIDGE IS BUILDING OUT AHEAD OF A
SYSTEM MOVING OUT OF ASIA.

.MODEL DISCUSSION...THERE ARE ONCE AGAIN MINOR DIFFERENCES IN
POSITION OF MAIN LOW CENTER AS WELL AS IN DEPICTION OF WEAK
TRIPLE POINT LOW DEVELOPMENT...BUT ALL MODEL SOLUTIONS SHOW
THE SAME GENERAL IDEA WITH EVOLUTION OF GULF STORM. MORE
SIGNIFICANT DIFFERENCES EVOLVE OUT WEST WITH FORMATION OF TRIPLE
POINT LOW EAST OF ADAK LATE MONDAY. THE ECMWF SOLUTION IS PREFERRED
SINCE IT SHOWS GOOD CONSISTENCY WITH ITS FURTHER NORTH POSITION
AND OTHER MODELS ARE TRENDING THAT DIRECTION.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE OCCLUDED FRONT...WHICH IS NOW ORIENTED
EAST-WEST WILL PIVOT AROUND THE GULF TONIGHT BECOMING ORIENTED
NORTH-SOUTH AND THEN DISSIPATE AS THE NORTHERN END OF THE FRONT
CONTINUE TO PUSH NORTH AND WEST TO COOK INLET ON SUNDAY. SO...KODIAK
WILL REMAIN WEST OF THE FRONT THE WHOLE TIME AND REMAIN ALL SNOW.
THERE WILL BE A BREAK TONIGHT AS THE LOW MOVES EASTWARD AND FLOW
SHIFTS TO NORTHWEST PUSHING ALL OF THE MOISTURE OFFSHORE.
HOWEVER...AS THE OCCLUDED FRONT BACKS IN FROM THE NORTHEAST
SUNDAY MORNING SNOW WILL REDEVELOP. AT THIS POINT DON'T EXPECT A
WHOLE LOT OF QPF ALONG THIS FRONT. THERE MAY BE A PERIOD OF STEADY
SNOW...BUT MOSTLY EXPECT PRECIP TO BE SHOWERY...SO THIS SHOULD
KEEP BLIZZARD CONDITIONS FROM DEVELOPING. ELSEWHERE...SNOW WILL
ACCOMPANY THE FRONT AS IT MOVES ACROSS SOUTHERN PORTIONS OF
SOUTHCENTRAL. HOWEVER...STRONG OFFSHORE FLOW...ESPECIALLY FROM THE
MAT-SU DOWN ALONG COOK INLET WILL MAINTAIN VERY DRY LOW LEVELS...SO
IT WILL TAKE A WHILE FOR ATMOSPHERE TO REACH SATURATION...AND ONCE
SNOW DOES REACH THE GROUND IT WILL BE LIGHT AND WON'T LAST FOR VERY
LONG. THE MAIN LOW WILL REMAIN IN THE GULF THROUGH MONDAY...SO THE
THREAT OF SNOW SHOWERS WILL PERSIST...MAINLY ALONG THE COAST.

BERING SEA/ALEUTIANS/SOUTHWEST ALASKA...THE WESTERN BERING RIDGE
WILL CONTINUE TO AMPLIFY AND PROGRESS EASTWARD AS ASIAN TROUGH
DIGS SOUTHEASTWARD. THIS WILL GRADUALLY BRING AN END TO SNOW
SHOWERS FROM WEST TO EAST...WITH SHOWERS ENDING LAST ALONG THE
ALASKA PENINSULA SUNDAY NIGHT AS THE RIDGE REACHES THE EASTERN
BERING. FORCING ALONG THE BASE OF THE RIDGE WILL THEN CAUSE IT
TO BECOME CUT-OFF OVER WESTERN ALASKA BY LATE MONDAY...WHICH WILL
BLOCK THE WESTERN BERING SYSTEM FROM ADVANCING PAST THE CENTRAL
BERING AND ALEUTIANS (SOMEWHERE AROUND 170W LONGITUDE).

.LONG TERM FORECAST...WESTERN ALASKA RIDGE WILL BUILD EASTWARD
NEXT WEEK BRINGING A PERIOD OF DRY WEATHER TO MAINLAND ALASKA.
MODELS DIVERGE AT THE END OF THE WEEK ON HOW THIS RIDGE WILL
BREAK DOWN...BUT IT DOES LOOK LIKE IT WILL PHASE WITH WESTERN
NORTH AMERICA RIDGE...WHICH WILL ALLOW STORMS TO TRACK TOWARD
MAINLAND ALASKA NEXT WEEKEND. WEST OF THE RIDGE...OCCASIONAL
SYSTEMS WILL PASS THROUGH THE REGION ON THERE WAY NORTHWARD
AROUND A LARGE SIBERIAN LOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 181.
MARINE...STORM WARNING...
         GALE WARNING...120 121 127 130 132 138 140 150 155 160
                        165 170 171 172 175 176 180 185.
         HEAVY FREEZING SPRAY WARNING...121 130 132 138 140 141
                                        150 155 165 170 171.
FIRE WEATHER...NONE.

SEB MAR 10