Gale Warning 1087, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
300 PM AKST SUN DEC 26 2010

.MODEL DISCUSSION...
THE MODELS ARE HAVING PROBLEMS HANDLING THE MULTIPLE VORTICES
ROTATING AROUND THE BROAD CYCLONIC CIRCULATION OVER THE GULF OF
ALASKA. SIMILAR PICTURE AS PREVIOUS DAYS WITH THE MODELS INITIALIZING
WELL ON SYNOPTIC FEATURES BUT THE NAM IS FAR SUPERIOR OVER THE GULF.
FOR THIS REASON...PREFER THE HIGHER RESOLUTION NAM IN THE SHORT TERM
AND WILL BE MAKING VERY FEW CHANGES TO THE MID TO LONG RANGE
FORECAST. THE SHORT TERM CHALLENGES WILL BE TIMING THE IMPACTS OF THE
MESOSCALE LOWS OVER THE NEXT 48 HOURS.

.ANALYSIS
UPPER LEVELS...A LARGE COMPLEX LOW PERSISTS OVER THE NORTHEASTERN
GULF OF ALASKA. THIS LOW IS AT THE BASE OF A BROAD TROUGH OVER MUCH
OF THE ALASKA MAINLAND. THE TROUGH IS ALLOWING A COLD ARCTIC AIRMASS
TO SPILL SOUTH ACROSS MUCH OF THE STATE. OUT WEST...A NEARLY
STATIONARY FRONTAL BOUNDARY NEAR THE WESTERN ALEUTIANS WILL MAKE SLOW
PROGRESS NORTHEAST WHILE THE ASSOCIATED LOW DEEPENS OVER THE NEXT 48
HOURS.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
.SOUTHCENTRAL...PARTLY TO MOSTLY CLOUDY SKIES ARE PREVAILING WITH
TEMPERATURES HOLDING BELOW CLIMATOLOGICAL NORM FOR THIS TIME OF YEAR.
A WEAK DISTURBANCE THAT ROTATED ALONG THE NORTH GULF COAST THIS
MORNING ONLY PRODUCED LIGHT SNOW SHOWERS FOR PART OF THE INLAND.
ANOTHER WEAK DISTURBANCE WILL BRUSH UP AGAINST THE COAST LATER
TONIGHT...ANTICIPATING SIMILAR RESULTS WITH LIGHT ACCUMULATION ALONG
THE COAST AND FLURRIES INLAND.

A CHANGE IN THE PATTERN WILL BEGIN TO TAKE SHAPE TUESDAY NIGHT AS THE
BROAD UPPER LEVEL LOW BREAKS DOWN AND THEN REDEVELOPS TO THE WEST.
THIS WILL ALLOW SOUTHWEST FLOW ALOFT TO PUSH ACROSS SOUTHCENTRAL...A
KEY INGREDIENT FOR CLOUDS AND SNOW TO RETURN TO THE INTERIOR. THIS
PROCESS WILL BEGIN TUESDAY NIGHT INTO WEDNESDAY WITH POSSIBLE BIG
SNOW EVENTS SHAPING UP LATER IN THE WEEK.

.SOUTHWEST MAINLAND...THE REMNANTS OF UPPER LEVEL DISTURBANCES MOVING
OVER THE VERY COLD AIRMASS IS RESULTING IN MARGINAL CONDITIONS AND
OCCASIONAL FLURRIES. TWO DISTINCT WAVES CAN BE SEEN OVER THE
SOUTHWEST MAINLAND THIS AFTERNOON WITH TWO MORE LINED UP TO MOVE OVER
THE SAME AREA. THIS WILL RESULT IN CONTINUE MOSTLY CLOUDY SKIES AND
PERIODS OF LIGHT SNOW.

THE PATTERN CHANGE LATER IN THE WEEK WILL RESULT IN MOISTURE MOVING
OVER THE ALASKA PENINSULA AND ALONG THE ALASKA RANGE. THE KUSKOKWIM
VALLEY MAY ESCAPE THE HEAVIER SNOW BUT WILL CERTAINLY SEE INCREASED
WINDS AS THE GRADIENT TIGHTENS UP WITH THE APPROACHING STORM.

.BERING SEA AND ALEUTIANS...WIDESPREAD SNOW SHOWERS CONTINUE ACROSS
MOST OF THE BERING SEA WITH COLD AIR ALOFT MOVING SOUTH OVER THE
RELATIVELY WARM WATERS. LOCAL GAP WINDS ACROSS THE ALASKA PENINSULA
COULD RESULT IN HIGH WIND WARNING CRITERIA...ESPECIALLY IN AREAS LIKE
KING COVE. THE STRONG WINDS AND HEAVY SNOW SHOWERS ARE BRIEF SO NO
BLIZZARD WARNINGS WILL BE ISSUED AT THIS TIME. WILL HAVE TO WATCH
MONDAY MORNING AS SOME ADDITIONAL ENHANCEMENT IS POSSIBLE AS AN UPPER
LEVEL VORT MAX SWINGS SOUTH ACROSS THE PENINSULA.

THE WINDS ALONG THE AFOREMENTIONED STATIONARY FRONT NEAR THE WESTERN
ALEUTIANS WILL GRADUALLY INCREASE THROUGH TUESDAY. THIS WILL BE A
RESULT OF THE ASSOCIATED LOW DEEPENING AND HIGH PRESSURE OVER THE
BERING PERSISTING. WINDS WILL INCREASE TO STORM FORCE BY MONDAY
AFTERNOON AND SPREAD TO THE CENTRAL ALEUTIANS AT THAT TIME. LATER
MONDAY NIGHT...MAY NEED TO CONSIDER BLIZZARD CONDITIONS NEAR ADAK AND
ATKA WHERE ENOUGH COLD AIR SHOULD REMAIN THROUGH THE EVENT.

.AER/ALU...WATCH/WARNING/ADVISORY SUMMARY
PUBLIC...WIND CHILL ADVISORY ZONE 131.
MARINE...STORMS 172 175 176
         GALES...127 185 411 413
         HEAVY FREEZING SPRAY...121 129 138 140 141 150 155 160 165
          179 180 185 412 414
FIRE WEATHER...NONE.

AB DEC 10