Blizzard in Alaska, April 15 to 16, 2010

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
615 AM AKDT TUE APR 13 2010

.ANALYSIS AND UPPER LEVELS...DOMINANT FEATURE IN THE UPPER LEVEL
PATTERN THIS MORNING IS THE LARGE VERTICALLY STACKED LOW CENTERED
OVER THE WESTERN BERING SEA WITH A 160KT 250MB JET STREAK MOVING INTO
THE CENTRAL ALEUTIANS AROUND THE SOUTHERN PERIPHERY OF THE LOW.
DOWNSTREAM OF THIS FEATURE A SHORTWAVE RIDGE IS MOVING INTO WESTERN
ALASKA WHILE A SHARP 500MB TROUGH IS ALIGNED OVER COOK INLET. STRONG
RIDGING IS IN PLACE OVER BRITISH COLUMBIA.

AT THE SURFACE THE MOST OBVIOUS FEATURE IS A LARGE FRONT MOVING
ACROSS THE CENTRAL BERING AND ALEUTIANS. BLIZZARD CONDITIONS HAVE
BEGUN IN THE PRIBILOF ISLANDS. AS THE SHORTWAVE RIDGE MOVES
EAST...MARINE STRATUS UNDER THIS RIDGE IS MOVING INTO COASTAL WESTERN
ALASKA...KEEPING SKIES CLOUDY. FURTHER DOWNSTREAM...THE SNOW HAS
TAPERED OFF ACROSS MUCH OF THE COOK INLET REGION AS THE LOW THAT
BROUGHT THE SNOW HAS MOVED INTO WESTERN PRINCE WILLIAM SOUND AND
DISSIPATED AND MOST OF THE PRECIP HAS MOVED EAST OVER PRINCE WILLIAM
SOUND WITH THE EXCEPTION OF AN OROGRAPHICALLY ENHANCED BAND OF LIGHT
SNOW THAT IS LINGERING OVER THE WESTERN CHUGACH MOUNTAINS AND
MATANUSKA VALLEY.

.MODEL DISCUSSION...MODEL AGREEMENT CONTINUES TO BE GOOD REGARDING
THE TIMING OF THE FRONT AS IT MOVES INTO THE EASTERN BERING AND INTO
THE WESTERN GULF HOWEVER BY SUNDAY THINGS BREAK DOWN. ALL MODELS
CONTINUE TO HAVE A HARD TIME HANDLING THE LOW IN THE BERING AFTER IT
DIVES SOUTHEAST INTO THE GULF. RUN TO RUN CONSISTENCY WITH THE GFS
AND THE ECMWF REMAINS POOR AND BOTH MODELS DISAGREE SHARPLY REGARDING
THE STRUCTURE OF THE BROAD LOW COMPLEX ONCE IT EMERGES IN THE GULF OF
ALASKA. THEREFORE...VERY FEW CHANGES ARE BEING MADE TO THE FORECAST
GRIDS FROM SUNDAY ONWARDS FOR THIS MORNING/S FORECAST PACKAGE.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...AS THE UPPER LEVEL SHORTWAVE TROUGH OVER COOK INLET
TRANSLATES EAST AND IS REPLACED BY A SHORTWAVE RIDGE EXPECT SKIES TO
CONTINUE CLEARING ACROSS THE KENAI AND COOK INLET REGIONS
TODAY...THOUGH THE SOUTHWESTERLY FLOW ALOFT WILL ALLOW FOR A FEW
SHOWERS TO LINGER AROUND THE MOUNTAINS INTO EARLY THIS AFTERNOON.
PRINCE WILLIAM SOUND AND THE COPPER RIVER BASIN WILL CONTINUE TO SEE
PRECIP INTO THIS EVENING AS THOSE AREAS REMAIN UNDER THE INFLUENCE OF
THE SHORTWAVE TROUGH. AFTER A BRIEF PERIOD OF CLEARING...THE NEXT
MAJOR FRONT MAKES ITS WAY INTO THE WESTERN GULF LATE TONIGHT. KODIAK
WILL FIRST FEEL THE EFFECTS OF THIS SYSTEM TONIGHT AS SNOW TONIGHT
CHANGES MIXES WITH RAIN TOMORROW. THE WARM ADVECTION WILL KEEP PRECIP
AS A MIX OF RAIN AND SNOW AS THE FRONT IMPACTS THE SOUTHERN KENAI AND
PRINCE WILLIAM SOUND ON FRIDAY...HOWEVER SNOW CAN BE EXPECTED IN THE
WESTERN SUSITNA VALLEY. THE SOUTHEASTERLY FLOW SHOULD KEEP THE
ANCHORAGE BOWL AND OTHER DOWNSLOPE AREAS RELATIVELY DRY...ALBEIT
CLOUDY. THIS WET PATTERN PERSISTS INTO THE WEEKEND AS THE FRONT
STALLS OVER THE REGION AND GRADUALLY DETERIORATES.

.BERING SEA/ALEUTIANS/SOUTHWEST...AS THE FRONT IN THE CENTRAL
ALEUTIANS MOVES EAST...BLIZZARD CONDITIONS ARE EXPECTED ALONG THE
KUSKOKWIM DELTA BY LATE THIS AFTERNOON AND POSSIBLY ALONG THE WESTERN
CAPES OF BRISTOL BAY BY THIS EVENING. WARMER AIR TO THE SOUTH SHOULD
ALLOW RAIN TO MIX WITH THE SNOW IN THE EASTERN ALEUTIANS AND AKPEN
...THUS MITIGATING ANY THREAT OF A BLIZZARD...THOUGH STRONG SOUTHERLY
WINDS CAN BE EXPECTED AS THE FRONT PASSES. BEHIND THE FRONT COLDER
AIR AIR FILTERS ACROSS THE BERING SEA AND WIDESPREAD SNOW SHOWERS CAN
BE EXPECTED INTO THE WEEKEND.

.LONG TERM FORECAST...AS MENTIONED ABOVE...VERY FEW CHANGES TO THE
LONG TERM FORECAST. THE DETAILS ARE SKETCHY RIGHT NOW BUT THE GENERAL
PATTERN THROUGH NEXT WEEK WILL HAVE A LARGE UPPER LOW ANCHORED IN THE
VICINITY OF SOUTHWEST ALASKA. AS A RESULT...THE GULF AND SOUTHCENTRAL
WILL BE UNDER SOUTHERLY FLOW AND THUS CAN EXPECT CLOUDY WEATHER TO
PERSIST FOR MUCH OF NEXT WEEK WITH WET WEATHER ALONG THE COAST AND
TEMPERATURES SLIGHTLY BELOW NORMAL...MAINLY DUE TO THE CLOUDY SKIES
EXPECTED. SOUTHWEST ALASKA WILL SEE SNOW SHOWERS FOR MUCH OF NEXT
WEEK DUE TO ITS PROXIMITY TO THE UPPER LOW WHILE THE BERING SEA AND
ALEUTIANS CAN EXPECT COOLER THAN AVERAGE TEMPERATURES UNDER NORTHERLY
FLOW WITH THE UBIQUITOUS SCATTERED SNOW SHOWERS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...151 195
MARINE...GALE WARNING...120 130 155 160 165 170 172 175 176 179 180
185
FIRE WEATHER...NONE

WOOD APR 10