Gale Warning 865, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
110 PM AKST SAT NOV 14 2009

.ANALYSIS AND UPPER LEVELS...A LARGE DEEP (AND COLD) UPPER LOW
IS CENTERED OVER MAINLAND ALASKA WITH ARCTIC AIR NOW COVERING ALL
BUT THE ALASKA PANHANDLE...AND THAT WILL CHANGE BY LATER TODAY.
SHORTWAVES EMBEDDED IN THE CYCLONIC ROTATION AROUND THIS CENTER
COMBINED WITH LOW LEVEL COLD ADVECTION AR PRODUCING WIDESPREAD
SNOW SHOWERS AND GUSTY WINDS ACROSS THE BERING AND ALEUTIANS AND
EASTWARD INTO THE GULF. POWERFUL STORM WHICH CROSSED THE GULF LAST
NIGHT IS NOW HEADING INLAND NEAR YAKUTAT...PRODUCING WIDESPREAD
SNOW ACROSS THE COPPER RIVER BASIN AND STRONG WINDS IN THE WAKE
OF THE LOW ACROSS THE GULF WATERS AND PRINCE WILLIAM SOUND REGION.
BLIZZARD WARNING FOR NORTHEAST PRINCE WILLIAM SOUND AND WINTER
WEATHER ADVISORY FOR SNOW FOR ZONE THE COPPER RIVER BASIN HAVE
BOTH BEEN EXTENDED THROUGH 4 PM THIS AFTERNOON.

.MODEL DISCUSSION...MODELS ARE IN FAIR AGREEMENT THROUGH THE FIRST
FEW DAYS OF THE FORECAST WITH EVOLUTION OF SYNOPTIC FEATURES.
LARGER DIFFERENCES THEN EVOLVE OUT WEST WITH POSITION OF GALE
FORCE FRONT AND LOW MOVING ALONG IT TUESDAY. ALL MODELS TRENDED
SOUTHWARD WITH FRONT...SO HAVE ADJUSTED FORECAST TO REFLECT
THAT...THEN STUCK WITH CURRENT FORECAST BEYOND TUESDAY AS SOLUTIONS
INCREASINGLY DIVERGE. IN THE EAST TRENDED TOWARD THE ECMWF IN THE
MID-TERM DUE TO GOOD RUN-TO-RUN CONSISTENCY.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...SNOW AND WINDS WILL DIMINISH IN THE WAKE OF
THE STRONG STORM MOVING INLAND ACROSS THE YUKON THIS AFTERNOON AND
EVENING. UPPER LOW AND TROUGH WILL REMAIN OVER SOUTHCENTRAL THROUGH
TUESDAY AND BEYOND WITH A SURFACE LOW OVER THE GULF. SHORT-WAVES
ROTATING AROUND THE LOW WILL PRODUCE PERIODS OF STRONGER WINDS AND
SNOW SHOWERS ACROSS THE GULF WATERS AND NORTH GULF COAST...WHILE
INLAND AREAS REMAIN COLD AND DRY. THE PRESSURE GRADIENT WILL
TIGHTEN ACROSS THE REGION MONDAY AS A STRONG LOW MOVES TO SOUTHEAST
ALASKA...SO GUSTY NORTHERLY WINDS WILL DEVELOP ACROSS THE
REGION...ESPECIALLY THROUGH THE TYPICAL BAYS AND PASSES.

SOUTHWEST ALASKA...A FEW SNOW SHOWERS WILL OCCASIONALLY MOVE
THROUGH COASTAL SOUTHWEST ALASKA THROUGH MONDAY AS UPPER SHORT-WAVES
PASS OVERHEAD. GUSTY WINDS WILL ALSO CONTINUE ALONG THE COAST AND
THROUGH THE ALASKA PENINSULA AS THE GRADIENT REMAINS TIGHT.
OTHERWISE...COLD AND DRY CONDITIONS WILL PERSIST ACROSS THE REGION.

BERING SEA/ALEUTIANS...A SHORT-WAVE OVER THE WESTERN BERING WILL
DROP DOWN INTO THE PACIFIC SUNDAY HELPING TO AMPLIFY THE UPPER
TROUGH CENTERED OVER MAINLAND ALASKA AND ALLOW RIDGE OVER SIBERIA
TO PROGRESS EASTWARD INTO THE BERING. THIS RIDGE WILL MOVE TO THE
EASTERN BERING MONDAY...GRADUALLY ENDING THE STRONG NORTHERLIES AND
SNOW SHOWERS FROM WEST TO EAST. A GALE FORCE FRONT ASSOCIATED WITH
A LOW MOVING TO THE SEA OF OKHOTSK WILL THE FOLLOW THE RIDGE INTO
THE BERING SUNDAY NIGHT AND MONDAY. THERE IS SOME UNCERTAINTY IN THE
DETAILS OF THE PROGRESSION OF THIS FRONT...BUT IT LOOKS LIKE IT WILL
UNDERCUT THE RIDGE TUESDAY WITH A LOW TRACKING ALONG THE FRONT TO
THE SOUTHERN ALASKA PENINSULA. MUCH WARMER AIR WILL ACCOMPANY THE
FRONT RESULTING IN A CHANGE FROM SNOW TO RAIN.

.LONG TERM FORECAST...THERE IS LOW CONFIDENCE IN TRACK OF INDIVIDUAL
STORMS IN THE EXTENDED PERIOD. HOWEVER...MEDIUM RANGE MODELS AGREE
MEAN TROUGH WILL REMAIN CENTERED OVER MAINLAND ALASKA...MAINTAINING
COLD AND DRY CONDITIONS...WHILE THE MEAN STORM TRACK SETS UP ALONG
THE ALEUTIANS EASTWARD TO THE GULF.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...120 150 155 160 165 170 171 172 175 176 180.
         HEAVY FREEZING SPRAY WARNING...160 179 180 185.
FIRE WEATHER...NONE.

SEB NOV 09