Blizzard and High Wind in Alaska, November 15 to 17, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
425 PM AKST TUE NOV 15 2011

.ANALYSIS AND UPPER LEVELS...
TODAY ABOVE THE GREAT LAND THE ATMOSPHERE FEATURES AN ELONGATED COLD
CORE LOW PRESSURE STRETCHING FROM THE BEAUFORT SEA DOWN THROUGH THE
COPPER RIVER BASIN. THE CLOSED SIBERIAN HIGH FROM YESTERDAY IS IN THE
PROCESS OF SLIDING SOUTH AND MERGING WITH A BUILDING RIDGE AHEAD OF A
SYSTEM TAKING SHAPE IN THE NORTHWEST PACIFIC. THE COMBINATION OF THE
BERING SEA/CHUKCHI PENINSULA RIDGE AND CLOSED LOW OVER EASTERN ALASKA
HAS CREATED A DEEP LAYER NORTHERLY FLOW WITH PARCEL TRAJECTORIES
COMING FROM THE ARCTIC OCEAN. THESE NORTH WINDS HAVE ENCOMPASSED MUCH
OF WESTERN ALASKA TODAY. A SHORTWAVE TROUGH IS CURRENTLY MOVING INTO
THE GULF OF ALASKA. AT THE SURFACE...THE MAJOR FEATURE IS A
DEVELOPING SURFACE LOW IN THE GULF OF ALASKA. BITTERLY COLD AIR AND
HIGH PRESSURE IS ANCHORED OVER THE CENTRAL INTERIOR. THE TIGHTENING
PRESSURE GRADIENT ALONG THE NORTH GULF COAST WILL ENHANCE THE COLD
NORTHERLY WINDS...ESPECIALLY FOR THE THOMPSON PASS AND COPPER RIVER
DELTA RESULTING IN BLIZZARD CONDITIONS. A STOUT SURFACE HIGH PRESSURE
SPREADS OVER MUCH OF THE BERING FROM EASTERN SIBERIA SOUTHEAST
THROUGH THE EASTERN ALEUTIANS. ANOTHER DEEPENING SURFACE LOW PRESSURE
MOVES TOWARD THE WESTERN ALEUTIANS FROM THE SOUTH TOWARD THE
KAMCHATKA PENINSULA.

.MODEL DISCUSSION...
MODEL AGREEMENT DOES NOT LAST VERY LONG FOR THE UPPER LEVEL
PATTERN AND EVEN LESS WITH THE SURFACE PATTERN. THOUGH THERE ARE SOME
EMERGING PATTERNS THAT CAN BE DISCERNED UNDERNEATH THE MODEL TO MODEL
DISCREPANCIES. FIRST...WHAT DO THE MODELS AGREE ON? THE SHORTWAVE
TROUGH MOVING INTO THE SOUTHERN GULF WILL MERGE WITH THE UPPER LOW
OVER EASTERN ALASKA SINKING SOUTH. ALSO THERE IS AGREEMENT AN UPPER
LEVEL RIDGE BUILDING OVER THE BERING AHEAD UPPER LOW IN THE FAR WEST
BERING. THE FEATURE THAT SEEMS TO BE GIVING MODEL GUIDANCE TROUBLE IS
A DOUBLE/TRIPLE BARREL UPPER LOW COMPLEX ROTATING OVER THE SEA OF
OKHOTSK. WHILE THE UPPER LOW WILL STAY IN ROUGHLY THE SAME PLACE
THROUGH THE WEEK A NUMBER OF SHORTWAVE TROUGHS PROPAGATING THROUGH
THE FLOW WILL MOVE NORTH BRINGING WARM AIR AND MOISTURE. WITHOUT ANY
UPPER LEVEL JET SUPPORT TO SPEAK OF SURFACE LOWS WILL MOVE NORTH WITH
THEIR UPPER LEVEL SHORTWAVES INTO THE WESTERN BERING AND A NEW TRIPLE
POINT LOW WILL FORM AND MOVE EAST. THE TIMING AND PLACEMENT OF THESE
FEATURES IS GOING TO BE HIGHLY VARIABLE.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...CONSIDERABLY COOLER AND DRIER WITH NORTHERLY
WINDS INCREASING THROUGHOUT THE DAY TODAY. DECREASING CLOUDS INTO THE
EVENING. TEMPERATURES NEAR ZERO AROUND THE ANCHORAGE BOWL AND
SLIGHTLY COLDER FOR THE MAT-SU AND COPPER RIVER BASIN. EXPECT SIMILAR
CONDITIONS THROUGHOUT THE WEEK.

SOUTHWEST ALASKA...CLEAR AND COLD IN AN OFFSHORE FLOW REGIME REMAINS
THE CASE FOR MOST OF THE SOUTHWEST INTERIOR. AREAS NEAR THE COAST
WILL REMAIN WARMEST. NORTHERLY WINDS WILL BE GUSTY IN THE BRISTOL BAY
AND ALASKA PENINSULA REGIONS. THESE CONDITIONS WILL STAY IN PLACE FOR
THE NEXT COUPLE DAYS.

BERING SEA AND ALEUTIANS...WHILE THE PATTERN REMAINS FAIRLY STAGNANT
IN THE EAST...THAT IS NOT THE CASE OUT WEST. A COMPLEX UPPER LOW OVER
KAMCHATKA WILL CONTINUE TO SPAWN TRIPLE POINT LOWS THROUGHOUT THE
WEEK. EXPECT WAVES OF RAIN FIRST IN THE WEST THEN SPREADING EAST
THROUGHOUT THE WEEK WITH GUSTY SOUTHERLY WINDS.

.LONG TERM FORECAST...
THE EXTENDED PATTERN REMAINS UP IN THE AIR AS OUR CURRENT SETUP
BEGINS TO BREAK DOWN IN THE SHORT TERM. LOOK FOR A VERTICALLY STACKED
LOW IN THE BERING THAT EVENTUALLY MERGES WITH A SOUTHWARD DROPPING
ARCTIC LOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131
         HIGH WIND WARNING 131 135
MARINE...STORM 130 132 150 175 176 185
         GALE 120 121 125 129 138 140 141 170 172 179
         HEAVY FREEZING SPRAY 121 129 130 138 140 141 160 180
FIRE WEATHER...NONE

MTL NOV 11