Blizzard in Alaska, December 24 to 25, 2008

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
230 PM AKST WED DEC 24 2008

.MODEL DISCUSSION...
MODELS IN REMARKABLY GOOD AGREEMENT TODAY GIVING SOME CONFIDENCE TO
THE FORECAST. THIS IS OFFSET BY THE POOR RUN TO RUN CONSISTENCY AND
POOR RECENT PERFORMANCE.

.ANALYSIS AND UPPER LEVELS...
MEAN UPPER RIDGE NEGATIVELY TILTED ALONG ABOUT 155 DEGREES WEST
LONGITUDE. STRONG AND PROGRESSIVE JET ON THE COLD SIDE (EASTERN) OF
THE HIGH FROM KODIAK SOUTHEASTWARD TO SAN FRANCISCO. INTERESTING
DYNAMICS ON THE WARM SIDE OF THE RIDGE WITH A LOW OVER THE CENTRAL
BERING SEA AND A LOW MOVING UP FROM THE SOUTH JUST EAST OF THE DATE
LINE. BOTH LOWS ARE JUICY...ESPECIALLY THE LATTER ONE.

.SHORT TERM FORECAST...
THE TWO LOWS WILL MERGE INTO AN ELONGATED FRONT SOMEWHAT TONIGHT...
BUT MOST OF THE MOISTURE FROM THE SOUTHERN LOW WILL STAY SOUTH OF 53
DEGREES NORTH LATITUDE. THE BERING LOW AND ITS LONG FRONT WILL MOVE
EAST AS THE UPPER RIDGE RETREATS SOUTHWARD...ON THE FIRST PART OF
ITS RETROGRADING JOURNEY.

PRECIPITATION FROM THE LOW SYSTEM WILL REACH THE WEST COAST OF
ALASKA BY EVENING AND SPREAD ACROSS SOUTHWEST ALASKA TONIGHT. AS
THE SURFACE LOW MOVES INTO KUSKOKWIM BAY EARLY THURSDAY MORNING
BLIZZARD CONDITIONS WILL DEVELOP OVER THE KUSKOKWIM DELTA AND
CONTINUE THROUGH EARLY AFTERNOON.

BY THURSDAY AFTERNOON THE FORMER BERING LOW WILL BE NEAR MCGRATH...
WITH A SECONDARY LOW ASSOCIATED WITH THE SOUTHERN SYSTEM DEVELOPING
JUST NORTHEAST OF KODIAK ISLAND. SIGNIFICANT SNOWFALL IS EXPECTED
OVER MOST OF SOUTHERN ALASKA THURSDAY AND THURSDAY NIGHT.

BY FRIDAY THE NORTHERN LOW WILL BE DISSIPATING OVER CENTRAL ALASKA
AND THE SOUTHERN SYSTEM WILL BECOME THE DOMINANT LOW. THE SURFACE
LOW WILL SPIN UP ALONG THE NORTH GULF COAST THROUGH FRIDAY AFTERNOON
WITH SNOW CONTINUING OVER SOUTH CENTRAL ALASKA. LOTS OF COLD
ADVECTION WITH NORTHWEST FLOW AT ALL LEVELS WEST OF THE LOW.

.LONG TERM FORECAST...
THE FEATURE OF NOTE FOR SATURDAY THROUGH THE REMAINDER OF THE
FORECAST (NEXT WEDNESDAY) AND BEYOND WILL BE THE BLOCKING RIDGE THAT
DEVELOPS OVER THE BERING SEA. THIS WILL ANCHOR THE UPPER LOW ALONG
ABOUT 140 DEGREES WEST LONGITUDE. SIBERIAN AIR WILL ROTATE AROUND
THE BLOCK AND ACROSS ALASKA USHERING IN A COLD EPISODE. EXACTLY HOW
COLD IT WILL GET AND OTHER DETAILS ARE SKETCHY AS THE ONLY FEATURE
WITH ANY FORECAST CONFIDENCE IS THE BLOCKING RIDGE ITSELF...ALL
DOWNSTREAM ACTIVITY WITH THE UPPER LOW IS SUBJECT TO NUMEROUS
NUANCES. BUT COLD TO VERY COLD IS LIKELY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 155.
MARINE...STORM WARNING 130.
         GALE WARNING 120 121 132 138 150 155 160 165 179 180 185.
         HEAVY FREEZING SPRAY WARNING 129 160 180 185.
FIRE WEATHER...NONE.

LUDWIG DEC 08