Small Craft Advisory 887, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SUN DEC 4 2011

.MODEL DISCUSSION...MODELS IN GENERALLY GOOD AGREEMENT THROUGH TUE
AFTERNOON. THE GFS/ECMWF START TO DIVERGE ON THE HANDLING OF THE LOW
COMPLEX OVER THE BERING SEA BEYOND THIS POINT. GENERALLY...MODEL
BLENDS WILL BE TOWARD THE GFS IN THE EAST. IN THE WEST...BLENDS WILL
CONSIST OF THE GFS THROUGH WED MORNING THEN TRANSITION TO AN ECMWF
BLEND OF OFFICIAL GRIDS TO MAINTAIN CONSISTENCY.

.ANALYSIS AND UPPER LEVELS...

.EAST...A STRONG COLD FRONT EXTENDING SOUTH THROUGH THE SUSITNA
VALLEY...KENAI PEN...AND TO THE WEST GULF THIS MORNING IS MOVING
RAPIDLY EASTWARD. STRONG GAP FLOWS IN ADVANCE OF THIS SYSTEM REACHED
WARNING LEVELS ACROSS TURNAGAIN ARM AND THE CHUGACH MOUNTAINS WITH
GUSTS TO 118 MPH REPORTED ALONG THE UPPER ANCHORAGE HILLSIDE. GAP
FLOWS WERE ALSO EVIDENT ALONG THE ALASKA RANGE AND THE COPPER RIVER
BASIN WHERE GUSTS NEAR 55 MPH WERE EVIDENT ALONG THE COPPER RIVER.
DEEP SOUTHERLY FLOW BROUGHT WARM TEMPERATURES AND MODERATE RAIN TO
LOW LYING AREAS AND MODERATE SNOW AT HIGHER ELEVATIONS ALONG THE
ALASKA AND COASTAL MOUNTAIN RANGES.

.EAST...THE STORM FORCE LOW CENTER NEAR THE BERING STRAIT IS MOVING
NORTHEAST AND WEAKENING. BRISK WEST TO SOUTHWEST WAS WINDS ARE
EVIDENT FROM THE CENTRAL BERING SEA TO OVER SW ALASKA. COLD ADVECTION
AND LAGGING UPPER TROUGH BROUGHT SNOW SHOWERS TO MUCH OF THE WEST
WITH SOME AREAS OF BLOWING SNOW EVIDENT OVER THE DELTA.

.SHORT TERM FORECAST...
.EAST...COLD AIR WITH INSTABILITY SHOWERS WILL SPREAD ACROSS
SOUTHCENTRAL ALASKA AS THE COLD FRONT MOVES INTO WESTERN CANADA LATE
TONIGHT. SNOW SHOWERS WILL LIKELY CONTINUE ACROSS SOUTHCENTRAL ALASKA
UNTIL UPPER TROUGH PASSAGE MON AFTERNOON. EXPECT BRISK SOUTHERLY
WINDS AND LOCALIZED GAP FLOWS BEHIND COLD FRONT TONIGHT AND MON
MORNING. A SECONDARY FRONTAL TROUGH MOVES TO THE WESTERN GULF WED AND
BRINGS IN A SHOT OF MOISTURE TO THE GULF COAST AND SOUTHCENTRAL.
PRESSURE GRADIENTS WILL INCREASE IN ADVANCE OF THE FRONT AND BRING
STRONG GAP FLOWS ESPECIALLY TO ALONG THE ALASKA RANGE...MATANUSKA
VALLEY AND ANCHORAGE BOWL.

.WEST...EXPECT SNOW SHOWERS ACROSS MUCH OF THE BERING SEA AND SW
ALASKA TONIGHT. A DEVELOPING STORM SYSTEM OVER THE NW PACIFIC MOVES
TO NEAR THE RAT ISLANDS TUE AFTERNOON. A SECONDARY CENTER THEN FORMS
JUST SW OF THE PRIBILOF ISLANDS TUE AFTERNOON. THE ASSOCIATED FRONTAL
TROUGH MOVES TO CENTRAL ALEUTIANS MON MORNING THEN WEAKENS AS IT
IMPACTS SW ALASKA TUE. A SECONDARY FRONT ASSOCIATED WITH THE LOW SW
OF THE PRIBILOF ISLANDS INTENSIFIES AND MOVES TO THE AK PEN TUE.
EXPECT WARMING TEMPS WITH A MIXTURE OF RAIN AND SNOW AS FRONTAL
TROUGH MOVES ACROSS THE BERING SEA AND INTO SW ALASKA.

.LONG TERM FORECAST...
ALTHOUGH THE VARIOUS FORECAST MODELS DISAGREE ON TIMING AND STRENGTH
OF VARIOUS SYSTEMS MOVING ACROSS THE AREA...THEY ALL AGREE IT WILL
BE QUITE ACTIVE WITH TEMPERATURES GENERALLY ON THE WARMER SIDE OF
NORMAL FOR THE EXTENDED PERIOD AND CHANCES OF PRECIPITATION FOR MOST
AREAS ON MOST DAYS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY FOR SNOW ZONE 145.
MARINE...STORM 170 171 172 175 176 185
         GALES 120 155 160 165 179 180 351 352
FIRE WEATHER...NONE.

RMC DEC 11