Heavy Freezing Spray Warning 147, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT THU MAR 22 2012

.ANALYSIS AND UPPER LEVELS...

THE WEATHER PATTERN OVER THE ANCHORAGE FORECAST OFFICE DOMAIN IS
FINALLY BECOMING A BIT MORE PROGRESSIVE...SUGGESTING A PATTERN CHANGE
IS ON THE WAY FOR THE SOUTHERN MAINLAND. LOW PRESSURE IN THE GULF AT
THE SURFACE AND ALOFT WILL GET SHUNTED TOWARDS SOUTHEAST ALASKA TODAY
AS UPPER LEVEL RIDGING MOVES EAST FROM THE BERING. THE IMPETUS FOR
THIS MOVEMENT EASTWARD IS A STRENGTHENING LOW APPROACHING THE WESTERN
BERING SEA FROM THE SOUTH THIS MORNING WHICH WILL PUSH A STRONG WARM
FRONT NORTH AND EAST ACROSS THE EASTERN BERING SEA TODAY AND INTO
SOUTHWEST ALASKA TONIGHT. THE PARENT LOW WILL REACH MAXIMUM STRENGTH
LATER TODAY AND TONIGHT OVER THE WESTERN BERING SEA NEAR 970 MB...
THEN WEAKEN THROUGH FRIDAY AND REMAIN STATIONARY JUST EAST OF THE
RUSSIAN COAST IN THE FAR WESTERN BERING. A TRAIN OF WEAKER LOWS WILL
MOVE NORTH AND EAST ALONG OR TO THE SOUTH OF THE ALEUTIANS FRIDAY
THROUGH THE WEEKEND.

.MODEL DISCUSSION...

MISSING SATELLITE DATA DUE TO A MALFUNCTION WITH THE GOES-15
GEOSTATIONARY SATELLITE MEANS A GREATER THAN NORMAL DEPENDENCE ON THE
MODELS FOR THIS FORECAST PACKAGE. LUCKILY...THE WEATHER PATTERN IS
PRETTY BENIGN OVER ALL BUT THE BERING SEA CURRENTLY. THE ONE TREND OF
NOTE IN ALL THE MODELS IS A FARTHER SOUTH DEVELOPMENT OF A TRIPLE
POINT LOW WHICH DEVELOPS ALONG THE FRONT MOVING EAST INTO THE WESTERN
GULF OF ALASKA FRIDAY AFTERNOON THROUGH FRIDAY NIGHT.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

UPPER LOW GETS SHUNTED EAST TODAY AS HIGH PRESSURE RIDGING ALOFT
MOVES OVER THE AREA LATE TONIGHT AND THE FIRST HALF OF FRIDAY. CLOUDS
AND LIGHT OVERRUNNING SNOW WILL IMMEDIATELY FOLLOW THE RIDGE AXIS
MOVING ACROSS THE ANCHORAGE AREA...WHICH MEANS THE BEST CHANCE AT
SOME LIGHT SNOW OVER THE REGION FOR THE NEXT FEW DAYS WILL BE FRIDAY
AFTERNOON. EXPECT ONLY VERY LIGHT ACCUMULATIONS BEFORE SOUTHEAST
WINDS PICK UP THROUGH TURNAGAIN ARM AND LIKELY RESULT IN DOWNSLOPE
DRYING OVER THE BOWL. OTHERWISE...WITH LOW PRESSURE NOW SLATED TO
DEVELOP FARTHER SOUTH ACROSS THE BOWL ABOUT THE ONLY CONCERN FOR ANY
PUBLIC ZONE WATCH/WARNINGS/ADVISORIES MIGHT BE SOME BLOWING SNOW
CONCERNS FOR THE PORTAGE VALLEY AND EASTERN TURNAGAIN ARM AREAS ON
FRIDAY.

SOUTHWEST ALASKA...

UPPER LEVEL RIDGING MOVES QUICKLY ACROSS THE REGION
TONIGHT...FOLLOWED IMMEDIATELY BY THE ARRIVAL OF A STRONG WEATHER
FRONT WHICH WILL LIKELY BRING BLIZZARD CONDITIONS ALONG THE KUSKOKWIM
DELTA COASTLINE EXTENDING SOUTH TO THE WESTERN CAPES TONIGHT. ANOTHER
AREA OF CONCERN FOR POSSIBLE BLIZZARD CONDITIONS DOWN THE LINE WILL
BE INLAND AREAS OF THE BRISTOL BAY ZONE WITH SOUTHEAST WINDS PUSHING
THROUGH THE GAPS IN THE ALEUTIAN RANGE COMBINING WITH SNOW FALLING
ALONG THE FRONTAL BOUNDARY. CONFIDENCE IS STILL TOO LOW TO ISSUE ANY
WARNINGS EXCEPT ALONG THE AFOREMENTIONED COASTAL AREAS.

BERING SEA/ALEUTIANS...

LOW PRESSURE STRENGTHENS INTO THE 970S TODAY OVER THE WESTERN BERING
SEA...AND WILL BE ACCOMPANIED BY STORM FORCE WINDS AROUND ITS CENTER
OF CIRCULATION. OUT AHEAD OF THE SYSTEM...A STRONG WARM FRONT WILL
PUSH NORTH ACROSS THE EASTERN ALEUTIANS...ALASKA PENINSULA...AND
PRIBILOFS. VERY COLD AIR AT THE SURFACE OVER THE PRIBILOFS ESPECIALLY
WILL ONLY SLOWLY ERODE WHILE MUCH WARMER AIR ALOFT WILL OVERRIDE THE
REGION. EXPECT BLIZZARD CONDITIONS DEVELOPING LATE THIS MORNING OVER
THE PRIBILOFS TO MIX WITH OR CHANGE OVER TO A PERIOD OF FREEZING RAIN
THIS AFTERNOON. THIS MAY ALSO OCCUR FOR A SHORTER DURATION OF TIME
OVER THE ALASKA PENINSULA. ANOTHER CONCERN WILL BE FOR THICK FOG AND
LOW VISIBILITIES AS THE WARMER AIR MASS MOVES OVER THE ICE PACK IN
PLACE. AS OF RIGHT NOW...NOT PLANNING ON ISSUING WHAT WOULD BE RATHER
RARE FREEZING RAIN ADVISORIES FOR THESE AREAS...BUT WILL CONTINUE TO
MONITOR OBSERVATIONS AND MODEL TRENDS.

.LONG TERM FORECAST...

SOUTHWESTERLY TO WESTERLY FLOW WILL LIKELY ALLOW FOR A TRAIN OF LOW
PRESSURE SYSTEMS TO MOVE WEST TO EAST FROM THE BERING SEA TO THE
SOUTHERN GULF. MODELS SEEM RATHER PERSISTENT IN KEEPING UPPER LEVEL
RIDGING OVER THE SOUTHERN MAINLAND...WHICH WILL LIKELY MEAN ANCHORAGE
WILL CONTINUE TO HAVE TO WAIT A WHILE TO BREAK THE SNOWFALL RECORD AS
SYSTEMS TRAVEL WELL SOUTH OF THE AREA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...155 161 195
MARINE...GALES...132 150 160 165 180 170 172 175 176 179
         STORMS...185
         HVY FRZG SPRY...130 150
FIRE WEATHER...NONE.

29/CC MAR 12