Gale Warning 980, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
605 AM AKST SAT DEC 19 2009

.ANALYSIS AND UPPER LEVELS...
AN UPPER LEVEL LOW IS CURRENTLY CENTERED AT THE NORTHERN EDGE OF THE
BERING SEA. AN ASSOCIATED TROUGH STRETCHES FROM THE CENTER OF THIS
LOW SOUTHEASTWARD ACROSS THE CENTER OF MAINLAND ALASKA AND INTO THE
NORTHERN TIP OF BRITISH COLUMBIA. FARTHER WEST...A WEAK RIDGE IS
CENTERED ALONG THE WEST EDGE OF THE ALASKA PENINSULA. FARTHER WEST A
BROAD TROUGH REGION SPREADS FROM THE CENTRAL ALEUTIAN ISLANDS WEST
TOWARDS RUSSIA WITH MULTIPLE LOWS. TWO SMALL CONNECTED LOWS OF ABOUT
EQUAL STRENGTH ARE NEAR THE WESTERN ALEUTIAN ISLANDS WITH ONE LOW
OVER SHEMYA. A TROUGH SPREADS EASTWARD TOWARDS BRISTOL BAY.  AN UPPER
LEVEL LOW IS FORMING AT THE PERIPHERY OF THIS TROUGH JUST NORTH OF
DUTCH HARBOR.  AT THE SURFACE...A SURFACE RIDGE IS BUILDING OVER MUCH
OF MAINLAND ALASKA AND THE EASTERN GULF AS THE BERING LOW RETROGRADES
FARTHER WEST.  A SURFACE LOW IS CENTERED OVER SHEMYA WHILE A POTENT
WARM FRONT STRETCHES FROM THIS LOW ACROSS BRISTOL BAY AND THE GULF. A
SECOND SURFACE LOW IS CENTERED OVER ATKA.

MODEL DISCUSSION...
MODELS FAIRLY CONSISTENT IN THE SHORT TERM SO NAM RELIED UPON DUE TO
ITS HIGHER RESOLUTION.  MODELS BEGIN TO DIVERGE ON THE POSITION OF
THE BERING LOWS BY MONDAY AND THEREFORE CONFIDENCE IS MEDIUM TO LOW
FOR THE LONG TERM. THE GFS WAS RELIED ON FOR THE LONG TERM DUE TO THE
GREATER RUN TO RUN CONSISTENCY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
AN APPROACHING WARM FRONT WILL BRING THE CHANCE OF WIDESPREAD SNOW
ALONG THE SOUTH CENTRAL GULF COAST SATURDAY ALONG WITH STRONG
WINDS...PARTICULARLY THROUGH TURNAGAIN ARM AND PORTAGE VALLEY WHERE
BLIZZARD CONDITIONS ARE EXPECTED. SNOW WILL BE HEAVIEST IN THE
SUSITNA VALLEY WEST OF THE PARKS HIGHWAY SATURDAY AND SUNDAY...WHERE
ADVISORY LEVEL ACCUMULATION IS EXPECTED. HOWEVER...DOWNSLOPING SHOULD
KEEP THE ANCHORAGE BOWL AND EASTERN MAT-SU VALLEY MAINLY IN SNOW
FLURRIES. TEMPERATURES WILL WARM CONSIDERABLY AFTER THE FRONT MOVES
ACROSS THE COAST SATURDAY AND THE INTERIOR SATURDAY NIGHT INTO
SUNDAY. SNOWSHOWERS WILL PERSIST ALONG THE COAST SUNDAY AFTER THE
PASSAGE OF THE FRONT DUE TO STRONG
ONSHORE FLOW.

.SOUTHWEST ALASKA...
AN APPROACHING FRONT FROM THE SOUTHWEST WILL BRING BOTH THE
POSSIBILITY OF HEAVY SNOW AND STRONG EAST AND SOUTHEAST WINDS ALONG
THE WESTERN CAPES OF BRISTOL BAY.  THIS WILL RESULT IN BLOWING SNOW
THROUGHOUT THE REGION SATURDAY WITH BLIZZARD CONDITIONS ALONG THE
WESTERN CAPES POSSIBLY NOSING INTO THE KUSKOKWIM DELTA LATE SATURDAY
INTO SUNDAY.  TEMPERATURES SHOULD INCREASE DRAMATICALLY AFTER THE
FRONT PASSES RESULTING IN POTENTIAL MIXED OR FREEZING PRECIPITATION.
HEAVIEST AMOUNTS OF SNOW WILL FALL ON EAST FACING SLOPES THROUGH
SUNDAY.

.BERING SEA/ALEUTIANS...
A SERIES OF PROGRESSING LOWS WILL GENERATE GALE AND STORM FORCE WINDS
ACROSS MUCH OF THE ALEUTIAN ISLANDS SATURDAY. IN ADDITION...RAIN AND
SNOW IS EXPECTED ACROSS MUCH OF THE ALEUTIAN CHAIN DUE TO WARMER
TEMPERATURES.

.LONG TERM FORECAST...
MODELS ARE INDICATING THAT THE LARGE TROUGH REGION OVER THE BERING
SEA AND THE RIDGE OVER THE MAINLAND AND EASTERN GULF WILL PERSIST
THROUGHOUT MUCH OF THE WEEK. AS A RESULT...STORMY CONDITIONS ARE
LIKELY TO PERSIST ALONG THE ALEUTIAN ISLANDS AND SOUTHWEST WHILE
ONSHORE FLOW WILL KEEP SNOWSHOWERS A POSSIBILITY ALONG THE GULF
COAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...125 161
         BLIZZARD WATCH...155
         WINTER STORM WATCH...161
MARINE...STORM...411 414 150 155 170 172
         GALE...351 352 412 414 120 125 130 132 138 140 160 165 171
                175 176 179 180 185
HEAVY FREEZING SPRAY...121 129 130 140 141 185

ELN/JAM DEC 09