Gale Warning 1006, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1105 PM AKST THU DEC 16 2010

.ANALYSIS AND UPPER LEVELS...BLOCKING RIDGE OVER THE BERING SEA
IS BEGINNING TO SHIFT EASTWARD AS A LOW MOVES UP THE WEST SIDE
INTO EASTERN RUSSIA AND A COLD FRONT PUSHES UP AGAINST THE RIDGE.
THIS IS HELPING TO PUSH THE VERTICALLY STACKED LOW OVER OVER THE
NORTHEAST PACIFIC SOUTHWARD AND ALLOW PRESSURE GRADIENT TO CONTINUE
TO SLACKEN ACROSS THE SOUTHERN MAINLAND AND EASTERN BERING SEA.
THUS...WINDS ARE SLOWLY DIMINISHING ACROSS THE REGION.

.MODEL DISCUSSION...MODELS STILL STRUGGLING WITH HANDLING OF LOW
MOVING TO THE WESTERN ALEUTIANS SATURDAY AND INTO THE BERING SUNDAY.
12Z GFS IS MUCH FASTER THAN PREVIOUS SOLUTIONS. PLAN TO STICK
CLOSE TO INHERITED FORECAST WHICH IS NOT TOO FAR FROM THE LATEST
NAM/UKMET/ECMWF SOLUTIONS.

.SHORT TERM FORECAST...

SOUTHWEST/SOUTHCENTRAL...CLEAR AND COLD CONDITIONS WILL PERSIST
THROUGH THE WEEKEND. AN UPPER LEVEL TROUGH WILL DROP DOWN OUT OF
THE ARCTIC TONIGHT AND SOUTHCENTRAL FRIDAY BEFORE FORMING A LOW
OVER THE GULF SATURDAY. THIS WILL BRING ANOTHER ROUND OF COLD
ADVECTION IN THE LOW LEVELS...ALTHOUGH NOT NEARLY AS STRONG AS
OCCURRED DURING THE RECENT WIND EVENT. MEANWHILE...THE SURFACE
PRESSURE GRADIENT WILL CONTINUE TO VERY SLOWLY SLACKEN UNTIL
COLDER AIR MOVES OVER THE GULF LATE FRIDAY CAUSING THE PRESSURE
TO DROP OVER THE GULF AND THE GRADIENT OVER SOUTHCENTRAL TO TIGHTEN.
THE LACK OF A STRONG LOW OVER THE GULF OR A REALLY TIGHT PRESSURE
GRADIENT WORKS AGAINST A WIDESPREAD WIND EVENT. THEREFORE...EXPECT
MOST OF THE IMPACT TO BE THROUGH THE TYPICAL MOUNTAIN GAPS. EASTERN
PRINCE WILLIAM SOUND WILL SEE THE STRONGEST DOWNWARD MOTION
ASSOCIATED WITH THE UPPER TROUGH AS WELL AS THE STRONGEST COLD
ADVECTION...SO THERE IS POTENTIAL FOR REACHING HIGH WIND CRITERIA
IN VALDEZ AND THROUGH THE COPPER RIVER DELTA. WILL ISSUE A HIGH
WIND WATCH FOR THESE AREAS WITH THE AFTERNOON PACKAGE. WINDS WILL
DIMINISH OVER THE WEEKEND AS COLD ADVECTION COMES TO AN END AND
THE SURFACE PRESSURE GRADIENT WEAKENS.

BERING SEA/ALEUTIANS...THE COLD FRONT ALONG THE WEST SIDE OF THE
RIDGE WILL RAPIDLY WEAKEN AS IT MOVES OVER TOP OF THE RIDGE TONIGHT
AND TO SOUTHWEST ALASKA FRIDAY. THERE MIGHT BE JUST ENOUGH MOISTURE
LEFT TO PRODUCE SOME SNOW ACROSS THE KUSKOKWIM DELTA...BUT ANYTHING
THAT DOES FALL WILL BE BRIEF AND LIGHT. THE NEXT SYSTEM IN
LINE...CURRENTLY OVER THE NORTHWEST PACIFIC WILL BUILD THE RIDGE
BACK UP A BIT AS IT TRACKS TO EASTERN RUSSIA LATE FRIDAY...BUT ALSO
FORCE THE RIDGE TO BECOME POSITIVELY TILTED. THIS WILL ALLOW THE
NEXT SYSTEM TO TAKE A MORE EASTWARD TRACK AND REALLY FLATTEN OUT
THE RIDGE AS IT CROSSES THE BERING ON SUNDAY.

.LONG TERM FORECAST...MODELS STRUGGLING WITH THE SYSTEM CROSSING
THE BERING SEA THIS WEEKEND AS THEY TRY TO DETERMINE HOW QUICKLY
THE RIDGE WILL FLATTEN OUT. IN ANY CASE THIS SYSTEM WILL AFFECT
SOUTHWEST ALASKA SOMETIME LATE INT THE WEEKEND INTO EARLY NEXT
WEEK. A RIDGE WILL REBUILD BEHIND THE SYSTEM WHICH WILL THEN FORCE
THE UPPER TROUGH TO DIG SOUTHEASTWARD INTO THE GULF. THERE ARE TOO
MANY UNCERTAINTIES IN HOW THIS ALL EVOLVES TO NAIL DOWN ANY DETAILS.
HOWEVER...BASED ON THE GENERAL PATTERN THERE WILL BE A GOOD SHOT
OF SNOW ACROSS ACROSS SOUTHCENTRAL FOLLOWED BY ANOTHER ARCTIC
BLAST...WHICH OF COURSE COULD PRODUCE ANOTHER WIND STORM.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...127 128 176.
         GALE WARNING...121 125 130 132 150 155 160 165 170 175 185.
         HEAVY FREEZING SPRAY WARNING...121 126 127 128 129 130 138
                                        140 141 150 160.
FIRE WEATHER...NONE.

SEB DEC 10