Gale Warning 872, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST WED NOV 16 2011

.ANALYSIS AND UPPER LEVELS...
VERY HIGH AMPLITUDE PATTERN TODAY...AN ELONGATED BROAD UPPER LOW
STRETCHES FROM THE BEAUFORT SEA WITH THE MAIN CORE OF THE LOW OVER
THE EASTERN GULF OF ALASKA. THE UPPER LOW IS PART OF A VERTICALLY
STACKED SYSTEM BRINGING SNOW AND RAIN TO THE GULF WITH STRONG WINDS
AND BLOWING SNOW FOR MUCH OF SOUTH CENTRAL ALASKA. ANOTHER STACKED
SYSTEM IS ANCHORED OVER THE KAMCHATKA PENINSULA BRINGING WIDESPREAD
RAIN AND GUSTY SOUTHERLY WINDS TO THE WESTERN AND CENTRAL ALEUTIANS.
THAT UPPER LOW AND ATTENDANT SHORTWAVE TROUGHS WILL BE THE FOCUS FOR
WEATHER IN THE COMING WEEK. BETWEEN THE TWO SYSTEMS A HIGH AMPLITUDE
RIDGE STRETCHES FROM THE NORTHERN PACIFIC THROUGH THE EASTERN
ALEUTIANS AND UP INTO SIBERIA ACCOMPANIED BY A DECENT PUSH OF
RELATIVELY WARM AIR INTO THE BERING SEA. ANOTHER SHORTWAVE/SURFACE
LOW COMBO IS CURRENTLY PASSING THE WESTERN ALEUTIANS BRINGING ANOTHER
ROUND OF RAIN.

.MODEL DISCUSSION...
GUIDANCE IS IN A BIT BETTER AGREEMENT WITH THE UPPER AIR FEATURES
TODAY. CONSISTENCY FROM YESTERDAYS RUNS ROUGHLY THE SAME WITH THE
MAJOR FEATURES...THE GULF LOW WILL DROP DOWN NEAR THE PANHANDLE AND
THE SHORTWAVE OVER THE WESTERN ALEUTIANS WILL MOVE NORTHWARD INTO THE
BERING SEA. TODAY'S PACKAGE IS IN MUCH BETTER AGREEMENT THROUGH THE
END OF THE WEEK WITH THE EVOLUTION OF INDIVIDUAL SHORTWAVES EMBEDDED
IN THE FLOW OF THE KAMCHATKA LOW. THE NEXT SHORTWAVE/WEAK TRIPLE
POINT LOW WILL PUSH INTO BRISTOL BAY AND THE AKPEN BY EARLY FRIDAY.
BY THE WEEKEND THE MODEL AGREEMENT STARTS TO BREAK DOWN. WHILE THE
EXACT PLACEMENT AND TIMING IS STILL IN QUESTION...THE ORIGINAL
KAMCHATKA UPPER LOW WILL DISSOLVE INTO ANOTHER IN EAST ASIA AND A NEW
UPPER LOW WILL FORM FROM THE NORTHERN PACIFIC INTO THE CENTRAL BERING
SEA. BOTH GLOBAL AND MESOSCALE MODELS HINT AT A DEEP SURFACE LOW IN
THE BERING PROPAGATING EASTWARD WITH A TRIPLE POINT LOW FORMING IN
THE VICINITY SOUTH OF KODIAK ISLAND BY THE WEEKEND.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...HIGH PRESSURE OVER THE INTERIOR AND LOW IN THE
GULF WILL KEEP THE GUSTY/WINDY CONDITIONS IN PLACE THROUGH THURSDAY.
BY THURSDAY EVENING THE PRESSURE GRADIENT WILL BEGIN TO RELAX AND
WINDS WILL SUBSEQUENTLY SLACKEN. THE HIGHEST WINDS WILL REMAIN IN THE
COPPER RIVER DELTA...THOMPSON PASS...AND MATANUSKA VALLEY AREAS. THE
WINDY CONDITIONS  WILL CAUSE BLOWING SNOW WITH INTERMITTENT REDUCTION
OF VISIBILITY. DRY CONDITIONS WILL REMAIN THROUGH THE WEEKEND.

SOUTHWEST ALASKA...BRISK NORTHERLY FLOW CONTINUES FOR EASTERN BRISTOL
BAY AND EASTERN KUSKOKWIM VALLEY. WINDS WILL SLACKEN AND TURN FROM
THE SOUTHEAST ON THURSDAY EVENING AHEAD OF AN INCOMING FRONTAL
BOUNDARY. RIGHT NOW THE FRONTAL BOUNDARY WILL JUST BRING SNOW TO
COASTAL AREAS AND THE AKPEN ON LATE THURSDAY EVENING CONTINUING INTO
FRIDAY. ANOTHER FRONTAL PUSH WILL BRING SNOW AGAIN ON SATURDAY...THIS
ONE SPREADING NORTHWARD THROUGH MOST OF THE SOUTHWEST INTERIOR.

BERING SEA AND ALEUTIANS...THE ACTIVE PATTERN OUT WEST CONTINUES.
RAIN WITH GUSTY SOUTHERLY WINDS WILL CONTINUE FOR THE WESTERN AND
CENTRAL ALEUTIANS. A FRONTAL BOUNDARY PUSHING EAST WILL BRING
PRECIPITATION TO THE EASTERN ALEUTIANS FIRST BEGINNING AS SNOW OR A
RAIN/SNOW MIX THEN TRANSITIONING TO ALL RAIN. A STRONGER LOW PRESSURE
WILL WORK NORTH TOWARD THE WESTERN CHAIN BY THE WEEKEND BRINGING
STRONG SOUTHERLY WINDS AND MORE RAIN.

.LONG TERM FORECAST...
LONG TERM GUIDANCE IN PRETTY GOOD AGREEMENT FROM MODEL TO MODEL.
LOOKS LIKE THE STACKED SYSTEM WILL PUSH INTO THE GULF BY THE END OF
THE WEEKEND WITH A BROAD AREA OF LOW PRESSURE. THE WESTERN ALEUTIANS
WILL STAY ACTIVE AS ANOTHER KAMCHATKA LOW TAKES SHAPE WITH ZONAL FLOW
CONTINUING FOR THE REST OF THE CHAIN. MOST OF THE SOUTHERN MAINLAND
LOOKS TO STAY DRY EXCEPT FOR COASTAL AREAS EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131 HIGH WIND WARNING 131 135 WIND CHILL
ADVISORY 145
MARINE...STORM 130 132 150 179 351 352 411 412 414 GALE 120 121 129
138 140 141 155 160 165 170 172 175 176 180 413 HEAVY FREEZING SPRAY
121 129 130 138 140 141 HURRICANE FORCE WIND WARNING 185
FIRE WEATHER...NONE

MTL NOV 11