Small Craft Advisory 263, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT FRI MAR 22 2013

.MODEL DISCUSSION...MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH ABOUT
84 HRS OUT WEST AND THROUGH ABOUT 60 HRS IN THE EAST. MODELS STRUGGLE
IN THE GULF BEYOND 60 HRS AS MULTIPLE CENTERS FORM IN BROADENING
PRESSURE TROUGH. FORECAST PACKAGES WITH GENERALLY BASED ON THE
NAM/ECMWF OUT WEST. IN THE EAST THE NAM AS USED EARLY ON...THEN
TRANSITIONED TO AN ECMWF BLEND FOR THE REMAINDER OF THE SHORT TERM.

.ANALYSIS AND UPPER LEVELS...

A MODERATE COLD FRONT IS MOVING ACROSS SW ALASKA AND SHOULD BE
CLEARING EASTERN BRISTOL BAY AROUND NOON AND THEN MOVING ACROSS COOK
INLET AND THE MATSU/ANCHORAGE BOWL LATER THIS AFTERNOON AND EVENING.
STRONG PRESSURE GRADIENTS IN ADVANCE OF THE FRONTAL ZONE ARE CREATING
STRONG GAP WINDS ACROSS SOUTHCENTRAL ESPECIALLY ALONG TURNAGAIN ARM.
BRISK SOUTH WINDS ARE ALSO DEVELOPING OVER THE COPPER RIVER BASIN.
MODERATE SNOW WAS FALLING OVER THE SUSITNA VALLEY AND SPREADING EAST
TOWARD THE ANCHORAGE BOWL.

FURTHER WEST...A WEATHER FRONT EXTENDS FROM THE WESTERN BERING SEA TO
OVER THE CENTRAL ALEUTIANS. STRONG SOUTHERLY WINDS AND RAIN ARE
EVIDENT ALONG THE FRONTAL ZONE WITH COOLER AIR WITH RAIN/SNOW SHOWERS
ON THE BACKSIDE...AS EVIDENCED BY THE PRESENCE OF OPEN CELL CU.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...THE COLD FRONT WILL MOVE ACROSS COOK
INLET...ANCHORAGE BOWL...AND THE MATSU VALLEYS THIS EVENING. A FAIRLY
STRONG BAND OF SNOW WILL BE ASSOCIATED WITH THIS FEATURE AS IT MOVES
THROUGH. IN THE MEANTIME...STRONG SOUTHERLY FLOW IN THE LOWER LEVELS
IS PRODUCING MODERATE SNOW OVER THE SUSITNA VALLEY AND ALONG THE
TALKEETNA MOUNTAINS. GUSTY SURFACE WINDS THROUGH FAVORED GAPS ACROSS
SOUTHCENTRAL COMBINED WITH FALLING SNOW WILL PRODUCE AREAS OF BLOWING
SNOW. BLIZZARD CONDITIONS ARE EXPECTED TO DEVELOP ALONG TURNAGAIN ARM
AND THE HILLSIDE THIS AFTERNOON AS SNOWFALL INTENSIFIES. COLD
ADVECTION AND SOME DRYING ARE EXPECTED AFTER FRONTAL PASSAGE
TONIGHT....THOUGH SOME SNOW SHOWERS WILL LINGER AROUND INTO THE
MORNING HOURS SAT. A LOW AND ASSOCIATED FRONTAL TROUGH MOVES SOUTH OF
THE AK PEN AND BRINGS INCREASING CHANCES OF SNOW TO THE GULF AND
SOUTHCENTRAL SUN.

.SW ALASKA...
WITH THE EXCEPTION OF A FEW SNOW SHOWERS OVER BRISTOL BAY THIS
EVENING...CONDITIONS SHOULD BECOME SOMEWHAT DRIER ACROSS THE REGION
TONIGHT. THE FRONTAL TROUGH OVER THE ALEUTIANS/AK PEN LOOKS LIKE IT
WILL MAINLY IMPACT THE BRISTOL BAY AREA WITH SNOW SAT AS ITS
ASSOCIATED LOW CENTER MOVES ACROSS THE AK PEN. CONDITIONS SHOULD
BECOME DRIER AGAIN SUN AS NORTHERLY FLOW SETS UP AGAIN SUN.

.ALEUTIANS AND BERING SEA...A WEATHER FRONT AND ITS ASSOCIATED LOW
MOVE RAPIDLY E/SE TONIGHT TO SOUTH OF THE AK PEN SAT EVENING. HIGH
PRESSURE BUILDS ACROSS THE BERING SEA SAT. A SECONDARY FRONT MOVES TO
THE WESTERN ALEUTIANS/WESTERN BERING SEA SUN.

.LONG TERM FORECAST...
AN ACTIVE WEATHER PATTERN WILL PERSIST THROUGH THE BEGINNING OF NEXT
WEEK WITH THE JET STREAM OVER THE ALEUTIANS AND SOUTHERN MAINLAND
DURING THAT TIME.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 101
MARINE...GALE WARNING 130 138 172 175 176.
FIRE WEATHER...NONE.

RMC MAR 13