Gale Warning 1061, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1030 AM AKST FRI DEC 17 2010

.ANALYSIS AND UPPER LEVELS...BLOCKING RIDGE OVER THE BERING SEA
IS BEING PUSHED TOWARD MAINLAND ALASKA AS A MODERATE STRENGTH
LOW MOVES UP THE WEST SIDE OF THE RIDGE TOWARD EASTERN RUSSIA.
A SHORT-WAVE TROUGH/SURFACE FRONT MOVING THROUGH THE TOP OF THE
RIDGE ARE RAPIDLY WEAKENING ALONG THE WEST COAST OF ALASKA. LIGHT
SNOW IS BEING OBSERVED ALONG THE KUSKOKWIM DELTA COAST BUT DON'T
EXPECT THE SNOW TO LAST VERY LONG OR MAKE IT VERY FAR INLAND.
ANOTHER SHORT-WAVE TROUGH IS DIGGING SOUTHWARD ACROSS EASTERN
ALASKA THIS MORNING TOWARD THE YUKON. THE TAIL END OF THE TROUGH
IS PASSING THROUGH SOUTHCENTRAL ALASKA WHICH WILL RESULT IN WEAK
COLD ADVECTION ACROSS THE COPPER BASIN AND DOWN TO EASTERN PRINCE
WILLIAM SOUND AND HELP KICK WINDS UP A BIT. THE MODEL TREND HAS
BEEN TO DIG THIS TROUGH FURTHER EAST...SO THE DOWNWARD MOMENTUM
WITH THE TROUGH AND THE EXTENT OF LOW LEVEL COLD ADVECTION ARE
GOING TO BE SIGNIFICANTLY LESS THAN ORIGINALLY THOUGHT. STILL...
THERE IS A HIGH WIND WARNING IN EFFECT FOR THOMPSON PASS WHERE IT
WON'T TAKE A WHOLE LOT OF FORCING TO GET WINDS FROM THE CURRENT
OBSERVATIONS OF 50 MPH UP TO WARNING LEVEL WINDS OF 75 MPH.

.MODEL DISCUSSION...MODELS ARE STILL STRUGGLING WITH THE TEMPORARY
PATTERN CHANGE THIS WEEKEND THROUGH EARLY NEXT WEEK AS BERING
RIDGE IS PUSHED SOUTHWARD ALLOWING A SYSTEM TO TRACK EASTWARD
ACROSS THE BERING. DO NOT PLAN ANY SIGNIFICANT CHANGES TO FORECAST
UNTIL MODELS SHOW A LITTLE MORE CONSISTENCY.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...WINDS WILL INCREASE IN THE VALDEZ AREA AS WELL
AS THROUGH THE COPPER RIVER DELTA THIS AFTERNOON THROUGH TONIGHT
WITH PASSAGE OF WEAK UPPER TROUGH AND ENSUING OF WEAK COLD ADVECTION.
AN UPPER LEVEL JET STREAK WILL MOVE THROUGH THE REGION ON SATURDAY
PROVIDING SOME SUPPORT FOR CONTINUED STRONG WINDS IN THESE AREAS.
THE SURFACE PRESSURE GRADIENT WILL REMAIN FAIRLY TIGHT AND STEADY
ACROSS THE REGION THROUGH SATURDAY...SO STRONG WINDS WILL ALSO
CONTINUE IN SEWARD/RESURRECTION BAY AND WHITTIER/PASSAGE CANAL.
THE GRADIENT WILL THEN SLACKEN SATURDAY NIGHT AND SUNDAY SO WINDS
SHOULD FINALLY DIMINISH IN THESE LOCATIONS. ELSEWHERE ACROSS THE
REGION...CLEAR AND COLD CONDITIONS WILL PERSIST THROUGH THE WEEKEND.

SOUTHWEST ALASKA...THE WEAK FRONT ALONG THE KUSKOKWIM DELTA WILL
DISSIPATE BY THIS AFTERNOON SO DON'T EXPECT MORE THAN A FEW HIGH
CLOUDS TO MAKE IT INLAND. OTHER THAN THE DELTA...HIGH PRESSURE
WILL PROVIDE CLEAR AND COLD CONDITIONS THROUGH SATURDAY. A FRONT
CURRENTLY OVER THE WESTERN BERING WILL REACH THE SOUTHWEST COAST
IN THE SATURDAY NIGHT SUNDAY TIME FRAME. THERE IS LOW CONFIDENCE
IN THE DETAILS OF ARRIVAL OF THE FRONT AS WELL AS HOW FAST IT WILL
MOVE THROUGH SOUTHWEST ALASKA. BOTTOM LINE THOUGH...EXPECT PRECIP
SOMETIME THIS WEEKEND INTO EARLY NEXT WEEK AS THIS FRONT PUSHES
THROUGH. THERE WILL BE QUITE A BIT OF WARM AIR ADVECTING ACROSS
THE BERING SO PRECIP MAY FALL AS RAIN IN COASTAL SECTIONS WHILE
LIKELY REMAINING ALL SNOW INLAND DUE TO THE DEEP ARCTIC AIRMASS
IN PLACE.

BERING SEA/ALEUTIANS...THE STRONG FRONT OVER THE WESTERN BERING
WILL ELONGATE AND WEAKEN AS THE PARENT LOW TRACKS UP INTO THE
ARCTIC. THE UPPER RIDGE WILL BECOME POSITIVELY TILTED ALLOWING
THE NORTHERN PORTION OF THE FRONT MAKE MORE EASTWARD PROGRESSION
THAN THE SOUTHERN PORTION. ALSO...LOWS WILL RIDE UP THE FRONT TO
THE VICINITY OF THE WESTERN ALEUTIANS...MAINTAINING A TIGHT PRESSURE
GRADIENT IN THAT REGION. AS RIDGE IS PUSHED DOWN INTO THE PACIFIC
LATE THIS WEEKEND WINDS AND PRECIP WILL SPREAD ACROSS MUCH OF THE
REGION.

.LONG TERM FORECAST...COMBINATION OF ENERGY MOVING ACROSS BERING
SEA OVER TOP OF THE PACIFIC RIDGE COMBINED WITH ARCTIC TROUGH
DIGGING ACROSS MAINLAND ALASKA WILL BRING A CHANCE OF SNOW TO
SOUTHCENTRAL EARLY NEXT WEEK. THIS WILL QUICKLY BE FOLLOWED BY A
BLAST OF ARCTIC AIR FROM THE EASTERN BERING TO MAINLAND ALASKA AND
THE GULF. ALTHOUGH MODELS HAVE STRUGGLED WITH THE DETAILS OF THE
TRANSITION TO THIS PATTERN...THERE HAS BEEN EXCELLENT CONSISTENCY
IN THE EVENTUAL OUTCOME. THEREFORE...CONFIDENCE IS HIGH THAT THERE
WILL BE ANOTHER WIND EVENT NEXT WEEK ALONG WITH FRIGID TEMPERATURES.
MEANWHILE...A BLOCKING RIDGE WILL REFORM BACK OVER THE CENTRAL TO
WESTERN BERING SEA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 131.
MARINE...STORM WARNING...127.
         GALE WARNING...121 126 128 129 172 175 176 185.
         HEAVY FREEZING SPRAY WARNING...121 126 127 128 129 140 141.
FIRE WEATHER...NONE.

SEB DEC 10