Small Craft Advisory 815, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AKDT WED OCT 22 2008

.MODEL DISCUSSION...
THE CURRENT SET OF MODELS ARE IN VERY GOOD AGREEMENT OVER THE
MAINLAND ALASKA AND THE GULF OF ALASKA THROUGH FRIDAY AFTERNOON. OUT
OVER THE BERING, THE MODEL DIFFER OVER THE STRENGTH OF THE LOW
DEVELOPING OVER THE WESTERN BERING TONIGHT AND HOW FAST IT WILL
WEAKEN OVER THE NEXT 2 DAYS. I LIKE THE GFS POSITIONS BUT THINK
PRESSURES ARE 2 TO 4 MB TOO DEEP AND WILL WEAKEN INTO A TROUGH SOONER
THAN MODEL INDICATES.

.ANALYSIS AND UPPER LEVELS...
AN SHORT-WAVE OVER THE SUSITNA VALLEY AND KENAI PENINSULA HAD
PRODUCED AREAS OF LIGHT SNOW AROUND ANCHORAGE, MATANUSKA AND SUSITNA
VALLEYS AND THE COPPER RIVER BASIN.

A LARGE SURFACE LOW SOUTH OF THE EASTERN ALEUTIANS WITH AN ASSOCIATED
WEATHER FRONT ACROSS THE CENTRAL BERING SEA AND ALASKAN PENINSULA
CONTINUES TO MOVE EAST. STORM FORCE WINDS WERE MAINLY ALONG THE
WESTERN HALF OF THE LOW WHERE THE COLD ADVECTION IS THE STRONGEST.
ANOTHER 974 MB LOW NEAR YAKUTAT THIS MORNING CONTINUES TO MOVE NORTH
INTO THE YUKON TERRITORY TODAY.

A RIDGE OF HIGH PRESSURE OVER THE WESTERN GULF AND SOUTHWEST ALASKA
HAS CLEARED SKIES OVER KODIAK ISLAND, BRISTOL BAY AND PARTS OF THE
KUSKOKWIM VALLEY.

.SHORT TERM FORECAST...
THE UPPER SHORT-WAVE WILL SWING NORTHEAST THROUGH THE COPPER RIVER
BASIN TONIGHT. AN UPPER RIDGE OVER THE WESTERN GULF WILL MOVE ACROSS
THE REST OF THE GULF AND INTO SOUTHEAST ALASKA BY THURSDAY MORNING.
AREAS OF SNOW WILL END OVER THE ANCHORAGE BOWL, MATANUSKA VALLEY AND
SUSITNA VALLEY BY LATE AFTERNOON AND SKIES WILL BEGIN TO CLEAR
TONIGHT. SNOW OVER THE COPPER RIVER BASIN WILL PERSIST THROUGH EARLY
TONIGHT.

THE LARGE 961 MB LOW SOUTH OF THE EASTERN ALEUTIANS WILL MOVE EAST
AND WEAKEN TO 979 MB OVER THE SOUTH GULF OF ALASKA THURSDAY AFTERNOON
THEN DISSIPATE THURSDAY EVENING. A 976 MB TRIPLE POINT LOW WILL
DEVELOP OVER THE WESTERN GULF TONIGHT THEN MOVE ONSHORE JUST EAST OF
CORDOVA THURSDAY EVENING AND INTO NORTHWEST CANADA FRIDAY. THE
ASSOCIATED WEATHER FRONT ACROSS THE ALASKA PENINSULA WILL MOVE
NORTHEAST INTO THE GULF OF ALASKA TONIGHT THEN WEAKEN AS IT MOVES
INLAND ACROSS PRINCE WILLIAM SOUND AND THE COPPER RIVER BASIN
THURSDAY AND THE YUKON TERRITORY FRIDAY. RAIN AND SNOW WILL MOVE INTO
KODIAK ISLAND THIS EVENING AND SPREAD TO THE SOUTHERN KENAI PENINSULA
AND PRINCE WILLIAM SOUND TONIGHT. SNOW WILL MOVE INTO THE COPPER
RIVER BASIN THURSDAY. SNOWS WILL BECOME SNOW SHOWERS THURSDAY NIGHT
AND FRIDAY.

STRONG COLD ADVECTION ON THE WEST SIDE OF THE LOW WILL PRODUCE STRONG
WINDS ACROSS KODIAK ISLAND, KENAI PENINSULA AND PARTS OF PRINCE
WILLIAM SOUND THURSDAY AND THURSDAY NIGHT. STRONGEST WINDS ARE
EXPECTED ALONG THE EAST SIDE OF CHANNELED TERRAIN ALONG THE ALEUTIAN
AND KENAI AND CHUGACH MOUNTAINS.

SOUTHWEST ALASKA WILL REMAIN PARTLY CLOUDY BUT DRY THROUGH THURSDAY
MORNING, BUT MORE CLOUDS AND SNOW SHOWERS ARE EXPECTED TO MOVE
THROUGH THE REGION AS AN UPPER TROUGH SWINGS DOWN FROM NORTHWEST
ALASKA THROUGH SOUTHWEST ALASKA THURSDAY.

.LONG TERM FORECAST...
THE COLD AIR WILL REMAIN OVER MAINLAND ALASKA AS HIGH PRESSURE BUILDS
OVER THE STATE THROUGH THE WEEKEND. A RIDGE OF HIGH PRESSURE WILL
MOVE ACROSS THE BERING SATURDAY, BUT A NEW STORM WILL MOVE INTO THE
BERING BY MONDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING FOR THE CENTRAL ALEUTIANS.
MARINE...STORM 130, 155, 170, 171
         GALE 120,125, 132, 138, 140, 150, 160
FIRE WEATHER...NONE.

NM OCT 08