Heavy Freezing Spray Warning 243, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SUN DEC 23 2012

.ANALYSIS AND UPPER LEVELS...IN THE UPPER LEVELS THERE IS A BROAD LOW
THAT IS CENTERED OVER THE ALASKA PENINSULA AND EXTENDS OVER MOST OF
SOUTHERN AND INTERIOR ALASKA. AN UPPER LEVEL RIDGE IS OVER THE ARCTIC
OCEAN AND EXTENDS THROUGH THE BERING STRAIT AND THEN SOUTH OF THE
CENTRAL ALEUTIANS. THE JET STREAM IS RUNNING SOUTH OF THE AREA AS IT
PARALLELS 40N ACROSS THE ENTIRE PACIFIC.
AT THE SURFACE THE IS A LOW COMPLEX WITH MULTIPLE CENTERS IN THE GULF
OF ALASKA. THE STRONGEST CENTER IS SOUTHEAST OF KODIAK ISLAND AND
SHOULD WEAKEN AS IT MOVES TO THE NORTHWEST THROUGH MONDAY. SOME SNOW
SHOWERS ARE ASSOCIATED WITH ANOTHER SMALL LOW NEAR THE SOUTHERN TIP
OF THE KENAI PENINSULA.
A FRONT MOVING INTO THE BERING SEA WILL HAVE A SERIES OF LOWS DEVELOP
ALONG IT AS IT STALLS IN THE SOUTHERN BERING SEA.

.MODEL DISCUSSION...THE MODELS ARE DOING WELL WITH THE POSITION AND
MOVEMENT OF THE LONG WAVES ON A HEMISPHERIC SCALE. HOWEVER ONE LOOKS
CLOSER AT THE DETAILS THERE IS MORE CAUSE FOR CONCERN. NONE OF THE
MODELS ARE DOING A PARTICULARLY GOOD JOB WITH ANY OF THE FEATURES
PAST A DAY OR SO OUT. THE BEST BET IN THE GULF OF ALASKA AND EASTERN
PART OF THE FORECAST AREA IS THE NAM MODEL. THE GFS IS PROBABLY THE
BEST OF THE BUNCH IN THE BERING SEA AND WESTERN PART OF THE FORECAST
AREA. HOWEVER THE ISSUES IN THE BERING SEA ARE MORE PRONOUNCED AS THE
MODELS ARE ALL STRUGGLING TO DEVELOP A SERIES OF LOWS THAT WILL
DEVELOP ALONG A FRONT THAT IS STALLING OUT IN THE SOUTHERN BERING
SEA.

.SHORT TERM FORECAST...THE BIGGEST WEATHER CONCERNS ARE IN THE
EASTERN KENAI PENINSULA ZONE WITH A BLIZZARD WARNING IN ZONE 125 FOR
TURNAGAIN PASS AND NORTHWARD. THIS WILL INCLUDE THE PORTION OF THE
SEWARD HIGHWAY FROM TURNAGAIN PASS AND ALONG TURNAGAIN ARM TO AROUND
BIRD POINT. WEST OF BIRD POINT THERE WILL ALSO LIKELY BE SOME BLOWING
SNOW BUT NOT ENOUGH TO WARRANT A BLIZZARD WARNING. THE WORST
CONDITIONS ARE EXPECTED TO BE NEAR PORTAGE WHERE THERE WILL BE HEAVY
SNOWFALL...POSSIBLY A FEW FEET BEFORE THE STORM ENDS...IN CONJUNCTION
WITH THE WINDS.
VERY COLD TEMPERATURES ARE IN THE COPPER RIVER BASIN AT 20 BELOW TO
30 BELOW. THOSE TEMPERATURES EXTEND THROUGH THOMPSON PASS WHICH HAS
REMAINED BETWEEN 15 BELOW AND 230 BELOW ALL DAY. WINDS FROM KEYSTONE
CANYON THROUGH THOMPSON PASS HAVE BEEN STRONG...DROPPING THE WIND
CHILL VALUES TO AROUND 45 BELOW ZERO. THIS WIND CHILL ADVISORY WILL
CONTINUE INTO MONDAY MORNING.
IN SOUTHWEST ALASKA THERE ARE SOME SNOW SHOWERS THAT HAVE DEVELOPED
IN THE BRISTOL BAY REGION THAT WILL PERSIST THROUGH THE NIGHT BEFORE
BECOMING MORE WIDESPREAD MONDAY. THESE SHOWERS WILL MOST LIKELY NOT
REACH AS FAR WEST AS THE BETHEL AREA AS THE LOW IS WEAKENING AND IS
EXPECTED TO DISSIPATE BEFORE IT MAKES IT TO THE KUSKOKWIM DELTA.
SNOW SHOWERS WILL PERSIST OVER THE ALASKA PENINSULA AND EASTERN
ALEUTIANS IN NORTHERLY FLOW WHILE THE OLD OCCLUDED FRONT IS
APPROACHING THE PRIBILOF ISLANDS. THIS OLD FRONT WILL BRING STEADY
SNOW TO THE PRIBILOF ISLANDS THROUGH AT LEAST THE EVENING HOURS.

.LONG TERM FORECAST...LOW CONFIDENCE IN THE MODELS MAKES THE LONG
TERM A BIT DIFFICULT. HOWEVER WHAT IS CLEAR IS THAT THERE WILL BE A
STRONG WARMING TREND OVER SOUTHERN ALASKA AS SOUTHEAST FLOW BRINGS IN
WARMER AIR AND AN ACTIVE PATTERN TO THE REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 125. WIND CHILL ADVISORY 131.
MARINE...GALE 120 125 130 140 172 175 176.
         HEAVY FREEZING SPRAY 121 130 140 141 160 165 185.
FIRE WEATHER...NONE.

DEC 12