Blizzard Warning 32, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST TUE DEC 31 2013

.ANALYSIS AND UPPER LEVELS...

TRANS PACIFIC ZONAL JET IS BEING DEFLECTED OVER THE GULF OF ALASKA BY
AN UPPER LEVEL RIDGE THAT COVERS THE GULF AND MAINLAND AK THIS
MORNING. LEFT EXIT REGION OF JET IS HELPING TO SPIN UP AN UPPER LOW
SOUTH OF THE AKPEN. ANOTHER UPPER LOW IS OVER THE CENTRAL BERING. AT
THE SURFACE...A WEAK LOW IS OVER THE CENTRAL BERING AND A BRAND NEW
LOW..WHICH IS THE MAJOR PLAYER OVER THE NEXT COUPLE OF DAYS...IS
SPINNING UP SOUTH OF SAND POINT. SURFACE HIGH PRESSURE IS CENTERED
OVER THE NORTHEAST PACIFIC AND THE ALASKA PANHANDLE.

.MODEL DISCUSSION...

MAJOR CHANGE IN MODEL SOLUTION DEVELOPED OVER THE LAST 12 HOURS AS
THE PREVIOUS IDEA OF A BRISTOL BAY LOW IS NOW A SHELIKOF STRAIT LOW.
MODELS ARE IN GOOD AGREEMENT THAT THE LOW SOUTH OF SAND POINT WILL
DEEPEN TO ITS LOWEST PRESSURE THIS AFTERNOON SOUTHEAST OF
CHIGNIK...AND THEN BEGIN TO WEAKEN AS IT SAILS THE LENGTH OF SHELIKOF
STRAIT TONIGHT AND THEN DISSIPATES WED AFTERNOON AND EVENING OVER
ANCHORAGE AND THE KENAI PENINSULA. BY THU ALL THAT REMAINS WILL BE A
DECAYING TROUGH OF LOW PRESSURE OVER THE NORTHERN GULF WITH HIGH
PRESSURE BUILDING OVER THE GULF AND MAINLAND AK ON FRI. WHILE THIS IS
HAPPENING...THE CENTRAL BERING LOW DISSIPATES AND A NORTH PACIFIC LOW
REACHES THE CENTRAL ALEUTIANS WED AFTERNOON...THE PRIBILOFS ON THU
AND THE BERING STRAIT ON FRI.

.SHORT TERM FORECAST...

SOUTHEAST OF THE ALASKA RANGE...GALE AND STORM FORCE WIND WITH RAIN
WILL SPREAD ACROSS KODIAK ISLAND THIS MORNING AND REACH THE NORTH
GULF COAST THIS AFTERNOON. PRECIPITATION WILL MOVE INLAND TONIGHT
MAINLY IN THE FORM OF SNOW. DOWNSLOPING WILL LIMIT THE AMOUNT OF
SNOWFALL FOR THE ANCHORAGE BOWL AND THE MATANUSKA AND SUSITNA
VALLEYS. CHANNELED TERRAIN WILL SEE GUSTY WINDS...AND THE POSSIBILITY
OF BLIZZARD CONDITIONS EXISTS TONIGHT FOR THOMPSON PASS. AS THE LOW
MOVES TO ANCHORAGE AND WEAKENS ON WED...RAIN AND SNOW SHOULD DIMINISH
FROM THE WEST...COMING TO AN END DURING THE DAY ON THU. PARTIAL
CLEARING AND DRY CONDITIONS WILL CONTINUE ON FRI.

SOUTHWEST ALASKA...THE FORECAST TODAY TURNS TO A RAPIDLY DEEPENING
LOW PRESSURE SYSTEM SOUTH OF THE ALASKA PENINSULA. LIGHT SNOW WILL
GRADUALLY SPREAD OVER BRISTOL BAY THIS MORNING FOLLOWED BY THE
KUSKOKWIM VALLEY AND KUSKOKWIM DELTA IN THE LATE AFTERNOON AND
EVENING HOURS. NORTHERLY WINDS WILL RAPIDLY INCREASE TOWARD THE
AFTERNOON HOURS LEADING TO AREAS OF BLOWING SNOW. BLIZZARD CONDITIONS
LOOK TO BE IN PLACE WITH VISIBILITY REDUCED TO ONE QUARTER MILE OR
LESS AT TIMES. THE WORST CONDITIONS WILL LIE NORTH AND WEST OF KING
SALMON IN THE INTERIOR OF THE BRISTOL BAY REGION. WARMER AIR SPILLING
THROUGH THE GAPS OF THE ALEUTIAN RANGE WILL BRING A MIX OF RAIN AND
SNOW ALONG THE ALASKA PENINSULA FROM KING SALMON SOUTHWARD. THE
SYSTEM WILL RAPIDLY WEAKEN ON WEDNESDAY AS IT MOVES TOWARD THE
SOUTHCENTRAL ENDING THE BLIZZARD THREAT. LIGHT SNOW REMAINS POSSIBLE
THROUGH LATE WEDNESDAY.

BERING SEA AND ALEUTIANS...A COMPLEX LOW SITS OVER THE WESTERN AND
CENTRAL BERING SEA BRINGING AREAS OF RAIN AND SNOW TO THE WESTERN AND
CENTRAL CHAIN. ON WED A FAST MOVING COMPACT SYSTEM WILL MOVE FROM THE
CENTRAL/WESTERN ALEUTIANS TO THE CENTRAL AND EASTERN BERING
SEA...BRINGING RAIN AND SNOW...AND SMALL CRAFT AND GALE FORCE WIND.

.LONG TERM FORECAST...

THE LONG TERM FORECAST WILL REVOLVE AROUND A STRONG STACKED SYSTEM
MOVING INTO THE WESTERN BERING SEA EAST OF THE KAMCHATKA PENINSULA.
THE BUILDING RIDGE OUT AHEAD OF THIS LOW PRESSURE WILL FIRST SEND THE
REMNANTS OF A COMPLEX BERING SEA LOW OVER THE MAINLAND BRINGING A
ROUND OF LIGHT SNOW OVER MANY LOCATIONS BEFORE THE RIDGE ITSELF
BEGINS TO ENCROACH ON THE MAINLAND. THE WILD CARD IN THE FORECAST IS
A CUT-OFF LOW IN THE NORTHCENTRAL PACIFIC THAT LOOKS TO GET PICKED UP
BY THE KAMCHATKA SYSTEM WHICH WILL DEVELOP A SURFACE LOW TOWARD THE
EASTERN ALEUTIANS/ALASKA PENINSULA...SENDING A FRONT UP INTO THE
NORTHERN GULF BY THE END OF THE WEEKEND/EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 131 BLIZZARD WARNING 161
MARINE...STORM 119 120 130 131 138 150 155 160
         GALES 125 127 132 136 137 139 140 141 165 172 173 174 175
               176 177 178 180
FIRE WEATHER...NONE

DS/ML DEC 13