Small Craft Advisory 657, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AKDT FRI AUG 21 2009

.ANALYSIS AND UPPER LEVELS...THE OLD LOW IN THE GULF OF ALASKA
CONTINUES TO MOVE SLOWLY EASTWARD AND THIS WILL BRING AN END TO THE
SHOWERS IN THE COPPER RIVER BASIN AND EASTERN PRINCE WILLIAM SOUND.
THE UPPER LEVEL RIDGE BEHIND THIS LOW IS KEEPING SOUTH CENTRAL ALASKA
AND THE EASTERN PART OF THE KUSKOKWIM VALLEY UNDER MOSTLY SUNNY
SKIES.
FARTHER WEST THE LONG WAVE UPPER LEVEL TROUGH CONTINUES TO DIG TO THE
SOUTHEAST. THE COLD FRONT ASSOCIATED WITH THIS WAVE WILL MOVE INTO
SOUTHWEST ALASKA TONIGHT AND INTO SOUTH CENTRAL ALASKA BY SUNDAY.

.MODEL DISCUSSION...IN THE SHORT TERM THEY ARE DOING VERY WELL.
THINGS BEGIN TO BREAK DOWN IN THE BERING SEA SUNDAY NIGHT WITH THE
GFS LOW BEING SIGNIFICANTLY DEEPER THAN THE NAM OR ECMWF. ALL THREE
MODELS VARY IN THE LOCATION OF THE CENTER AS WELL. AFTER THIS THE
WHEEL COME OFF AND THERE IS VERY LITTLE CONFIDENCE IN ANY SOLUTION
PRESENTED FOR THE BERING SEA AREA. BY TUESDAY AND TUESDAY NIGHT THE
GFS AND ECMWF HAVE A RIDGE OR A MODERATE LOW RESPECTIVELY IN THE
CENTRAL BERING SEA. THE SYSTEM IN THE EARLY PART OF NEXT WEEK IS THE
REMNANT OF AN OLD TYPHOON AND MODELS ARE USUALLY VERY BAD AT
RESOLVING THESE SYSTEMS. NOT MANY IF ANY CHANGES WILL BE MADE PAST
THREE DAYS IN THE FORECAST AS THERE IS SUCH LOW CONFIDENCE IN ANY
MODEL AT THIS POINT.

.SHORT TERM FORECAST...EXPECT RAIN TO DEVELOP IN SOUTHWEST ALASKA AND
THEN THE BRISTOL BAY REGION AS THE COLD FRONT MOVES INTO THE AREA.
SOUTH CENTRAL ALASKA WILL SEE INCREASING CLOUDS SATURDAY WITH RAIN
DEVELOPING SUNDAY.
STRONG SUBSIDENCE BEHIND THE FRONT IS CREATING AN UNUSUALLY CLEAR
AREA IN THE WESTERN AND CENTRAL BERING SEA. THE PRIBILOF ISLANDS MAY
SEE A LITTLE SUNSHINE BEHIND THIS FRONT AS A RESULT.

.LONG TERM FORECAST...THERE IS LOW CONFIDENCE IN THE LONG TERM
FORECASTS DUE TO THE HUGE DISPARITY IN MODELS SOLUTIONS RESOLVING THE
REMNANTS OF THE OLD TYPHOON MOVING TOWARD THE BERING SEA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

AUG 09