Small Craft Advisory 842, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST MON NOV 21 2011

.ANALYSIS AND UPPER LEVELS...A COLD UPPER LEVEL LOW REMAINS
ENTRENCHED OVER THE INTERIOR OF THE STATE WITH AN UPPER LEVEL RIDGE
IN THE CENTRAL BERING SEA. BY TOMORROW THE UPPER LOW WILL DROP INTO
THE NORTHERN GULF OF ALASKA AND THE UPPER RIDGE WILL DRIFT EASTWARD
AND WEAKEN. THE PATTERN OF AN UPPER LOW OVER THE MAINLAND PART OF THE
STATE WITH AN UPPER RIDGE OVER THE BRING SEA WILL PERSIST THROUGH
MOST OF THE WEEK.

.MODEL DISCUSSION...MODELS ARE DOING ACCEPTABLE FOR THE COMPLEX LOW
IN THE GULF AND A WEAK TRIPLE POINT LOW DEVELOPING ALONG THE WEATHER
FRONT IN THE BERING SEA TUESDAY NIGHT. THESE UNCERTAINTIES MAY CAUSE
SOME TIMING ISSUES WITH PRECIPITATION BUT THE OVERALL PATTERN IS
HANDLED WELL ON ALL THE MODELS. THE NAM WAS THE MOST PREFERRED MODEL
ON BOTH THE EAST AND WEST AREAS TODAY.

.SHORT TERM FORECAST...THE STRENGTHENING LOW IN THE GULF WILL
INCREASE THE PRESSURE GRADIENT IN THE GULF ZONES AS WELL AS THE REST
OF SOUTH CENTRAL ALASKA. THE INCREASING PRESSURE GRADIENT IN
CONJUNCTION WITH COLD AIR ADVECTION AND DOWNWARD VERTICAL MOTION
SHOULD PRODUCE WARNING LEVEL WINDS GUSTS (75 MPH) AROUND CHANNELED
TERRAIN IN KODIAK ISLAND THIS EVENING THROUGH TOMORROW AFTERNOON.
WINDS WILL INCREASE ALL OVER SOUTH CENTRAL AND THE GULF REGION BUT
THE STRONGEST WINDS ARE EXPECTED TO BE OVER KODIAK ISLAND.
SNOW WILL ALSO DEVELOP ALONG THE NORTH GULF COAST AND FROM THE
MATANUSKA VALLEY SOUTHWARD IN CONJUNCTION WITH THE GULF LOW. THE
WINDS AND SNOW COMBINATION HAS PROMPTED A BLIZZARD WARNING THIS
EVENING THROUGH TOMORROW AFTERNOON IN THE EASTERN KENAI PENINSULA
ZONE 125. EXPECT AREAS OF NEAR ZERO VISIBILITIES IN THE BLOWING SNOW
DURING THIS PERIOD. THERE WILL ALSO BE REDUCTION OF VISIBILITY IN
THOMPSON PASS WITH THIS SYSTEM BUT LAST WEEKS STRONG STORM SCOURED
THE TRANSPORTABLE SNOW OUT OF THE PASS AND NEARBY AREA LEAVING ONLY
FALLING SNOW TO REDUCE VISIBILITIES. AT THIS TIME IT LOOKS AS THOUGH
THE PRECIPITATION WILL NOT BE ENOUGH TO CAUSE BLIZZARD CONDITIONS SO
THE BLIZZARD WATCH FOR THOMPSON PASS WAS CANCELED. WHILE CONDITIONS
ARE NOT EXPECTED TO BE ACTUAL BLIZZARD CONDITIONS THERE WILL BE
STRONG WINDS AND BLOWING SNOW REDUCING VISIBILITIES IN THOMPSON PASS
THROUGH TOMORROW AFTERNOON. WIND CHILLS WILL ALSO BE 35 TO 50 BELOW
ZERO IN THOMPSON PASS THROUGH WEDNESDAY MORNING.

SOUTHWEST MAINLAND...NORTHERLY WINDS TO CONTINUE AS VERY COLD
AIR MOVES INTO THE AREA. WIND CHILLS WILL APPROACH OR REACH ADVISORY
LEVEL ACROSS THE LOWER KUSKOKWIM VALLEY AND BRISTOL BAY ZONE AS WELL
AS ACROSS THE KUSKOKWIM DELTA BEGINNING THIS EVENING. THIS WILL BE
SOME OF THE COLDEST AIR OF THE SEASON SO FAR.

IN THE BERING...UNCHARACTERISTICALLY QUIET WEATHER FOR THIS TIME OF
YEAR WILL CONTINUE THROUGH MIDWEEK AS HIGH PRESSURE MOVES SLOWLY
EASTWARD THROUGH THE BERING SEA.

.LONG TERM FORECAST...ANOTHER COLD WEEK IS ON TRACK FOR MAINLAND
ALASKA. THE LONG RANGE MODELS ARE HINTING AT A PATTERN CHANGE BY NEXT
WEEKEND...WHICH MAY BRING A LITTLE WARMER BUT SNOWIER PATTERN TO THE
MAINLAND. HOWEVER CONFIDENCE IN A PATTERN CHANGE IN THE LONGER TERM
PORTIONS OF THE FORECAST IS DIFFICULT AND MAKES CONFIDENCE LOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 125.
         HIGH WIND WARNING 171.
         WIND CHILL ADVISORY 131 152 155.
MARINE...GALE 129 140 155 160.
         STORM 132 138 150.
         HURRICANE FORCE WIND 130.
         HEAVY FREEZING SPRAY 121 129 130 132 138 140 141 160 185.
FIRE WEATHER...NONE.

NOV 11