Snow Advisory 6, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AST THU JAN 24 2008

.MODEL DISCUSSION...MODELS ARE IN GOOD AGREEMENT WITH NOT MUCH TO
DISCUSS. BOTH GFS AND NAM HAVE BEEN USED TO DETERMINE SNOW AMOUNTS IN
THE EASTERN DOMAIN.

.ANALYSIS AND UPPER LEVELS...UPPER LEVEL RIDGE AXIS IS OVER THE
CENTRAL GULF OF ALASKA INTO THE COPPER RIVER BASIN THIS AFTERNOON.
THIS AXIS IS MOVING EAST AS THE STRONG UPPER LEVEL JET PUMPS MOISTURE
INTO MAINLAND ALASKA. THIS JET STREAM IS RUNNING DUE NORTH UP THE
170W MERIDIAN STARTING FROM SOUTH OF THE 30N PARALLEL. THE MAIN LOW
AT THE SURFACE IS IN THE NORTHWEST BERING SEA AND HAS BEEN DETACHED
FROM THE UPPER LEVEL SUPPORT AND WILL RAPIDLY WEAKEN AND MOVE
EASTWARD THROUGH TOMORROW.

.SHORT TERM FORECAST...A STRONG 850 TEMPERATURE GRADIENT IS SETTING
UP FROM SOUTHERN COOK INLET P THE SUSITNA VALLEY AND WILL HELP CAUSE
A SIGNIFICANT AMOUNT OF OVERRUNNING SNOW TONIGHT. THE SNOW IN
SOUTHWEST ALASKA WILL BEGIN TO END FROM THE WEST THROUGH THE EVENING.

AN ITEM THAT HAS BEEN CLOSELY LOOKED AT TODAY IS THE POSSIBLE
DEVELOPMENT OF BLIZZARD CONDITIONS IN TURNAGAIN ARM THIS EVENING. THE
WINDS WILL BE STRONG ENOUGH AND THERE IS GOING TO BE SNOW. THE
QUESTION IS WHETHER THERE WILL BE HEAVY ENOUGH TO CAUSE VISIBILITIES
TO DROP ALL THE WAY TO ONE QUARTER MILE. WHAT IS VERY LIKELY IS THAT
IT WILL HAVE A SIGNIFICANT IMPACT ON TRAVEL THROUGH TURNAGAIN ARM
THIS EVENING AND OVERNIGHT. THEREFORE WHILE THERE IS STILL SOME
UNCERTAINTY IN THE VISIBILITIES GOING QUITE THAT LOW...A BLIZZARD
WARNING IS WARRANTED.

STRONG NORTHWEST WINDS WILL BEGIN TO DEVELOP BEHIND THIS SYSTEM AS
THE UPPER LEVEL JET TURNS NORTHWEST AND ADD SUPPORT TO THE COLD
ADVECTION BEHIND THIS SYSTEM.

.LONG TERM FORECAST...SKIES WILL CLEAR AGAIN BEHIND THIS SYSTEM FOR
MOST OF THE WEEKEND IN SOUTH CENTRAL ALASKA. SOUTHWEST ALASKA WILL BE
CLEARING OUT FOR THE BEGINNING OF THE WEEKEND AND THEN SEE INCREASING
CLOUDS WITH A CHANCE OF SNOW. EXPECT COLD TEMPERATURES WITH THE CLEAR
SKIES. THE BERING SEA AREA WILL BE A LITTLE MORE MODERATE WITH A LOW
IN THE WESTERN BERING SEA BRINGING IN CLOUDS AND SNOW SHOWERS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 101 111.
MARINE...GALE 120 121 129 132 138 150 155 160 165 170 172 175 176 179
180 185.
         STORM 130.
         HEAVY FREEZING SPRAY 121 129 130 138 140 141 185.
FIRE WEATHER...NONE.

JAN 08