Ice Storm in Alaska, November 12, 2002

SOUTH/SOUTHWEST ALASKA FORECAST DISCUSSION
10 PM AST MON NOV 11 2002

ANALYSIS AND FORECASTS...
THE MAJOR UPPER LOW WILL ANCHOR OVER THE BERING STRAIT THROUGH
THU AS ITS TROF DIGS SOUTH SOUTHEAST INTO THE WESTERN GULF OF
ALASKA AND INTO THE NORTH PACIFIC. INITIALLY THE RESULTING
SOUTHERLY FLOW WILL RESULT IN A GENERAL WEAK WARM ADVECTION
PATTERN OVER THE SOUTH CENTRAL REGION TO THE PRINCE WILLIAM SOUND
AND ALONG THE GULF COAST AREAS. AS THE UPPER TROF DIGS TO THE
SOUTH COLD ADVECTION AROUND THE WEST SIDE OF THE ANCHORING LOW
WILL PUSH THE UPPER LEVEL COLD AIR THROUGH THE EASTERN BERING SEA
TO THE NORTH PACIFIC SOUTH OF THE ALASKA PENINSULA BY WED
AFTERNOON. AT THE SURFACE THIS BRINGS THE LOW SOUTH OF THE
ALEUTIANS TO SOUTH OF KODIAK ISLAND WED THEN THE LOW BECOMES
NEARLY STATIONARY AS IT SLOWLY WEAKENS. THE LOW NOW SOUTHWEST OF
THE QUEEN CHARLOTTS WILL ROTATE NORTH NORTHEAST UP ALONG THE GULF
COAST TO SOUTH OF PRINCE WILLIAM SOUND BY WED AFTERNOON. HERE THE
FORECAST MODELS DIVERGE ON THE SOLUTION TO THE NEXT DAY OR TWO.
LOOKING TO THE ENSEMBLE SOLUTIONS WE FAVOR THE CURRENT AVN
SOLUTION THAT KEEPS THE LOW IN THE SOUTHERN SOUND MORE ORGANIZED.
WE ALSO EXPECT SOME MODERATE COLD ADVECTION TO OCCUR FROM THE
SOUTHERN YUKON TERRITORY ACROSS THE COPPER RIVER BASIN TO THE
SOUTH CENTRAL REGION THROUGH TUE NIGHT. THUS ANTICIPATE THE
POSSIBILITY OF A WARM ADVECTION SNOW SCENARIO TO EVOLVE ACROSS
THE SOUTH CENTRAL REGION WED NIGHT INTO THU. HOWEVER, AS THE
SURFACE LOW MOVES TO SOUTH OF THE SOUND EXPECT ENOUGH WARM
ADVECTION WITH THIS OVER THE SOUND TO RESULT IN PRECIP MAINLY OF
THE LIQUID VARIETY WED NIGHT AND THU.

TO THE WESTERN ZONES THE MAIN SHORT TERM FEATURE IN THE UPPER
LEVEL LOW THAT IS NOW EXITING TO THE NORTHEAST. THE LOW LEVEL
SOUTHWEST FLOW UP INTO THE KUSKOKWIM VALLEY IS KEEPING LIGHT SNOW
OR SNOW AND FOG OVER THE VALLEY. AMOUNTS OF SNOW HAVE THUS FAR
BEEN EXTREMELY LIGHT AND WE CANCELED THE SNOW ADVISORY BUT STILL
SEE A POSSIBLE 1 TO 3 INCHES OF ACCUMULATION THROUGH TUE MORNING.

ACROSS THE CHAIN THE LOW SOUTH OF THE ALEUTIANS MOVES EAST AS
PREVIOUSLY DISCUSSED. THIS RESULTS IN A NORTH TO NORTHWEST FLOW
ACROSS THE BERING SEA THROUGH WED BEFORE A SURFACE RIDGE MOVES
INTO THE REGION LATE WED. THIS RIDGE WILL RAPIDLY BE PUSHED TO
THE EAST AND FLATTEN AS A MODERATE LOW MOVES INTO THE WESTERN
BERING SEA THU.

.AFC...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 12AB 13.
FIRE WEATHER...DONE.

SAM NOV 02