Heavy Freezing Spray Warning 113, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKDT SUN APR 3 2011

.ANALYSIS AND UPPER LEVELS...A VERY ACTIVE PATTERN CONTINUES WITH A
LARGE UPPER LEVEL TROF OVER MAINLAND ALASKA AND ANOTHER TOWARD THE
KAMCHATKA PENINSULA. A SHORTWAVE RIDGE IS CURRENTLY LOCATED BETWEEN
THESE TWO DOMINANT FEATURES OVER THE CENTRAL BERING SEA. THE SURFACE
PATTERN REFLECTS THE UPPER LEVELS WITH A LARGE OCCLUDED LOW SOUTH OF
KODIAK ISLAND. THE FRONTAL BOUNDARY EXTENDS NORTH AND EAST AND THEN
BACK TOWARD THE PANHANDLE...WITH WIDESPREAD STORM FORCE WINDS
OBSERVED ALONG THIS BOUNDARY. COLD AIR FILTERING SOUTH ON THE BACK
SIDE OF THE LOW AIDED BY A 75 KT LOW LEVEL JET IS PROVIDING HAZARDOUS
CONDITIONS ACROSS THE ALASKA PENINSULA AND EASTERN ALEUTIANS.

.MODEL DISCUSSION...ALL MODELS IN EXCELLENT AGREEMENT THROUGH 84
HOURS. THE ENSEMBLE MEAN IS ALSO IN LINE WITH THE OPERATIONAL MODEL
RUNS ADDING CONFIDENCE TO OUR AFTERNOON PACKAGE.

.SHORT TERM FORECAST...
ALEUTIANS/BERING SEA...THE NEXT FRONTAL BOUNDARY TO IMPACT THE BERING
SEA AND EVENTUALLY MAINLAND ALASKA HAS ALREADY CROSSED SHEMYA EARLY
THIS AFTERNOON. A TRIPLE POINT WILL DEVELOP ALONG THIS BOUNDARY AND
RAPIDLY SHOOT THE MOISTURE EAST...REACHING BRISTOL BAY AND THE
KUSKOKWIM DELTA BY LATE MONDAY MORNING. STRONG WINDS FROM THE EASTERN
ALEUTIANS TO THE ALASKA PENINSULA WILL DIMINISH THIS
EVENING...ALLOWING BLIZZARD CONDITIONS TO IMPROVE. THIS IS IN
RESPONSE TO THE RAPIDLY APPROACHING SYSTEM OUT WEST. WINDS ON THE
BACKSIDE COULD REACH HIGH WIND WARNING CRITERIA BRIEFLY ACROSS THE
WESTERN ALEUTIANS.

SOUTHWEST ALASKA...
A LARGE DEFORMATION ZONE ASSOCIATED WITH THE KODIAK LOW CONTINUES TO
PRODUCE SNOW AND BLOWING SNOW ALONG THE KUSKOKWIM DELTA COAST.
CONDITIONS WILL RAPIDLY IMPROVE OVERNIGHT AS THE BOUNDARY MOVES
INLAND. A VERY SHORT BREAK IS EXPECTED BEFORE RAIN AND SNOW SPREAD
INLAND MONDAY MORNING. WIDESPREAD SNOW SHOWERS WILL PERSIST ACROSS
SOUTHWEST ALASKA BY MONDAY AFTERNOON...DIMINISHING IN COVERAGE SLOWLY
THROUGH TUESDAY. TRANSIENT HIGH PRESSURE BUILDS AGAIN WEDNESDAY
BEFORE THE NEXT STRONG FRONTAL BOUNDARY MOVES INLAND WEDNESDAY
EVENING.

SOUTHCENTRAL ALASKA...
THE FRONTAL BOUNDARY BUTTING UP AGAINST THE GULF COAST REACHED ITS
PEAK STRENGTH THIS MORNING AND WILL CONTINUE TO WEAKEN THROUGH THE
AFTERNOON AND EVENING HOURS. STORM FORCE WINDS ALONG THIS BOUNDARY
WILL DIMINISH TO SMALL CRAFT ADVISORY BY EARLY MONDAY MORNING. THE
LOW THAT IS POSITIONED SOUTH OF KODIAK ISLAND WILL FILL RAPIDLY AS IT
DRIFTS EAST TOWARD THE THE ALASKA PANHANDLE. A TRANSIENT UPPER LEVEL
RIDGE WILL MOVE OVER SOUTHCENTRAL MONDAY. THE AFOREMENTIONED RAPIDLY
APPROACHING SYSTEM WILL IMPACT SOUTHCENTRAL ALASKA BY MONDAY
AFTERNOON AND EVENING.

THE VORT MAX AND SOUTHWESTERLY FLOW ALOFT AHEAD OF THE SYSTEM WILL
PROVIDE AMPLE LIFT FOR RAIN AND SNOW ACROSS MUCH OF SOUTHCENTRAL. WE
WILL BEGIN TO ADVERTISE MORE LIKELY WORDING FOR RAIN AND SNOW
SOMETIME LATE MONDAY NIGHT OR TUESDAY...STILL NOT CONFIDENT IN TIMING
OF PRECIP AT THIS POINT. COLDER AIR ALOFT IS SLOW TO MOVE BACK ACROSS
THE REGION SO WARMER TEMPERATURES AT THE SURFACE MAY LIMIT SNOWFALL
ACCUMULATION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 181
         HIGH WIND WARNING 191
MARINE...STORM WARNING...155 176
         GALE WARNING...120 130 138 150 160 165 170 171 172 175 179
                        185
         HEAVY FREEZING SPRAY WARNING...160 185
FIRE WEATHER...NONE.

AB APR 11