Heavy Snow Warning 4, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
555 AM AST MON DEC 24 2007

.ANALYSIS AND UPPER LEVELS...
A VERY STRONG LOW PRESSURE APPROACHING THE SOUTH END OF KODIAK
ISLAND EARLY THIS MORNING IS BY FAR THE MOST PRESSING FORECAST ISSUE
IN THE SHORT TERM. THIS LOW INTENSIFIED RAPIDLY OVERNIGHT AS IT
MOVED NORTH TOWARD KODIAK. SNOW AND LOCALIZED BLIZZARD CONDITIONS
HAVE BEGUN OVER PORTIONS OF KODIAK ISLAND ALREADY EARLY THIS
MORNING. COOL WEST TO NORTHWEST FLOW DOMINATES THE BERING/ALEUTIANS.
A MESOSCALE SURFACE LOW PRESSURE JUST WEST OF THE PRIBILOFS EMBEDDED
IN THE WEST NORTHWEST FLOW IS BRINGING SNOW AND WINDS TO THE
PRIBILOFS THIS MORNING.

THE KODIAK LOW PRESSURE WILL MOVE EAST NORTHEAST THROUGH TONIGHT.
SEE SHORT TERM FORECAST FOR MORE DETAILED DISCUSSION OF ITS IMPACTS.

.MODEL DISCUSSION...
MODEL PERFORMANCE HAS UNFORTUNATELY GONE DOWNHILL. REGARDING THE BIG
LOW PRESSURE JUST SOUTH OF KODIAK...GFS HAS BEEN QUITE INCONSISTENT
IN ITS TRACK. NAM/WRF CONSISTENCY HAS NOT BEEN OUTSTANDING
EITHER...BUT WE ARE FAVORING IT FOR THE TRACK OF THE LOW BECAUSE IT
AGREES WITH THE UKMET AND ECMWF AND ITS INITIALIZATION HAS BEEN
BETTER. THIS FAVORED TRACK IS FOR THE LOW TO COME TO CRAWL TODAY
JUST SOUTH OF KODIAK ISLAND...THEN MOVE EAST TONIGHT. IN
GENERAL...THIS FORECAST PACKAGE REFLECTS A SLOWER MOVEMENT OF THE
LOW TODAY...THEN A MORE SOUTHERLY TRACK OF THE PRIMARY LOW TONIGHT.
OUT WEST...MODELS ARE HANDLING A SMALL SCALE LOW JUST WEST OF THE
PRIBILOFS QUITE POORLY. THERE ARE ALSO SOME VERY LARGE MODEL
DISAGREEMENTS ON A MAJOR LOW TUESDAY NIGHT INTO WEDNESDAY FOR THE
WEST. GFS AGAIN IS HORRIBLY INCONSISTENT...BOUNCING A FEW HUNDRED
MILES NORTH AND SOUTH FROM RUN TO RUN. NONE OF THE MODELS ARE THAT
GREAT AT THIS POINT...AND WE ARE GOING WITH A MIDDLE OF THE ROAD
TRACK FOR THIS LOW FOR NOW.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
VERY STRONG LOW PRESSURE IN THE WESTERN TO CENTRAL GULF TODAY AND
TONIGHT WILL BRING STORM FORCE TO HURRICANE FORCE WINDS. STRONG
WINDS WILL OCCUR ALL AROUND THE LOW...BUT THE VERY STRONGEST WINDS
WILL BE TONIGHT ON THE BACKSIDE OF THE LOW AS THE LOW MOVES EAST AND
AWAY FROM KODIAK ISLAND. BLIZZARD WARNING IN EFFECT FOR KODIAK
ISLAND THROUGH MIDNIGHT TONIGHT. EVEN THOUGH THE SNOW ALONG THE GULF
COAST OF THE ISLAND MAY BE WET ENOUGH TO LIMIT BLIZZARD CONDITIONS
TODAY...BLIZZARD CONDITIONS WILL OCCUR ALL ALONG ON THE WEST SIDE OF
THE ISLAND...AND BLIZZARD CONDITIONS WILL SPREAD OVER THE ENTIRE
ISLAND LATE THIS AFTERNOON AND TONIGHT AS THE COLDER AIR AND
NORTHWEST WINDS KICK IN ON THE BACKSIDE OF THE LOW. WILL ALSO ISSUE
A SNOW ADVISORY FOR AROUND KACHEMAK BAY. WILL HAVE TO KEEP A CLOSE
EYE ON THE EASTERN KENAI FOR POSSIBLE BLIZZARD TODAY...BUT WILL NOT
ISSUE ANYTHING AT THIS MOMENT AS TEMPERATURES AT LOWER ELEVATIONS
MAY BE A LITTLE TOO WARM AND DUE TO THE REMAINING UNCERTAINTY IN THE
LOW TRACK. IN THE UPPER COOK INLET REGION TODAY INCLUDING
ANCHORAGE...EXPECT SOME LIGHT SNOW OR FLURRIES THIS AFTERNOON AND
EVENING...BUT NOTHING MAJOR. HOWEVER...THINGS STILL LOOK INTERESTING
FOR THE COOK INLET REGION CHRISTMAS DAY. ALTHOUGH THE MAIN LOW
PRESSURE PASSES WELL SOUTH OF THE AREA IN THE NORTH CENTRAL GULF...A
WELL DEFINED TROUGH AXIS WILL EXTEND UP NORTH INTO PRINCE WILLIAM
SOUND. VERY STRONG COLD ADVECTION WILL BE PRESENT IN COOK INLET WITH
SOME REMAINING ENERGY AND MOISTURE...AND THERE COULD BE SOME
ACCUMULATIONS FOR THE NORMALLY DRIER WESTERN KENAI NORTH TO
ANCHORAGE...PALMER...AND TALKEETNA. HIGH PRESSURE BUILDS IN TUESDAY
NIGHT AND WEDNESDAY.

SOUTHWEST MAINLAND...
GENERALLY QUIET WEATHER WILL BE PRESENT OVER THE SOUTHWEST MAINLAND
THROUGH THE NEXT FEW DAYS. A MAJOR EXCEPTION COMES THIS AFTERNOON
AND TONIGHT AS MOISTURE SPILLS OVER THE ALEUTIAN AND ALASKA RANGES
FROM THE LOW IN THE GULF. ACCUMULATING SNOW IS EXPECTED MAINLY FROM
KING SALMON AND SLEETMUTE EAST...WITH PERHAPS SOME BLOWING SNOW
ALONG THE ALEUTIAN RANGE.

BERING SEA/ALEUTIANS...
SOME SNOW AND BLOWING SNOW IS OCCURRING IN COLD BAY THIS MORNING ON
THE BACKSIDE OF THE KODIAK LOW...AS WELL AS IN SAINT PAUL IN
RELATION TO THE MESOSCALE BERING LOW. BOTH OF THESE CONDITIONS
SHOULD BE FLEETING. SHOWERY WESTERLY FLOW WILL PERSIST THROUGH
TONIGHT OVER THE WHOLE REGION. THEN A MAJOR LOW WHOSE TRACK IS
UNCERTAIN MOVES FROM WEST TO EAST ALONG THE CENTRAL TO EASTERN
ALEUTIANS/BERING TUESDAY AND WEDNESDAY.

.LONG TERM FORECAST...
LOTS OF UNCERTAINTY IN THE EXTENDED...BUT GENERALLY WE EXPECT
COOL...SHOWERY CONDITIONS OVER THE CENTRAL/WESTERN BERING AND
ALEUTIANS. MOST OF THE LOW PRESSURE AREAS WILL TRACK NEAR OR SOUTH
OF THE EASTERN ALEUTIANS AND ALASKA PENINSULA...AND INTO THE GULF OF
ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 171.
MARINE...HURRICANE FORCE WIND WARNING ZONES 130 132 352.
         STORM WARNING ZONES 120 138 140 150 351.
         GALE WARNING ZONES 121 125 129 141 160 165 170 171 172 175
          179 413 414.
         HEAVY FREEZING SPRAY WARNING ZONES 121 130 132 138 140 141
          150 160 165 180 185 411 412 414.
FIRE WEATHER...NONE.

FOISY DEC 07