Heavy Freezing Spray Warning 72, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SAT FEB 25 2012

.ANALYSIS AND UPPER LEVELS...A RATHER PROGRESSIVE UPPER LEVEL FLOW IS
OVER SOUTHERN ALASKA AND THE BERING SEA WHICH WILL CONTINUE INTO THE
FIRST PART OF NEXT WEEK. CURRENTLY THE MAJOR ACTION IS RELATED TO THE
LARGE LOW IN THE CENTRAL BERING SEA AND THE FRONT THAT EXTENDS AHEAD
OF IT INTO SOUTHWEST ALASKA. THIS SYSTEM WILL CONTINUE MOVING
EASTWARD AND IS THE FOCUS OF MOST OF THE WEATHER IN THE AREA.

.MODEL DISCUSSION...MODELS SOLUTIONS ARE DOING QUITE WELL WITH GOOD
AGREEMENT BETWEEN THE GFS NAM AND ECMWF. THE BIGGEST DIFFERENCE IS
THE GFS BRINGS WARMER AIR A LITTLE FARTHER NORTH IN THE GULF REGION
TONIGHT THROUGH SUNDAY NIGHT. THIS WARMER SOLUTION IS LIKELY TO
VERIFY. THE NAM AND GFS BOTH SHOW SOME DOWNSLOPE IN THE ANCHORAGE
AREA AND WESTERN KENAI PENINSULA TONIGHT INTO SUNDAY NIGHT WITH THE
HIGHER RESOLUTION NAM SHOWING IT BEST. THIS WILL BE A FACTOR IN THE
PRECIPITATION AMOUNTS IN THESE AREAS.

.SHORT TERM FORECAST...
SOUTH CENTRAL...THERE ARE STILL SOME AREAS OF UNCERTAINTY WITH THE
APPROACH OF THE FRONT. THE BIGGEST QUESTION IS THE AMOUNT OF SNOWFALL
OVER THE ANCHORAGE AREA AND WESTERN KENAI PENINSULA. THE NAM AND GFS
ARE BOTH SHOWING SOME DOWN SLOPE OVER THESE AREAS WHICH WILL LIMIT
THE AMOUNT OF PRECIPITATION. HOWEVER THE UPPER LEVEL FLOW IS
SOUTHWEST WHICH IS FAVORABLE FOR INCREASED PRECIPITATION AMOUNTS. AT
THIS TIME IT LOOKS LIKE MOST OF THE ANCHORAGE BOWL AND WESTERN KENAI
PENINSULA NORTH OF CLAM GULCH WILL SEE SOME SNOW BUT NOT HUGE
AMOUNTS. THIS WILL BE THE CASE TONIGHT THROUGH SUNDAY BUT THE
DOWNSLOPE WILL END BY SUNDAY EVENING ALLOWING SNOWFALL AT THAT TIME.
THERE WILL LIKELY BE A SHARP GRADIENT IN SNOWFALL AMOUNTS UP THE
ANCHORAGE HILLSIDE AND THE BLIZZARD WARNINGS IN PORTAGE AND TURNAGAIN
ARM AND ANCHORAGE HILLSIDE AREAS STILL LOOK GOOD.
THE WINTER STORM WARNING FOR HEAVY SNOW FOR THE HOMER BLUFF AREA
STILL LOOKS REASONABLE AS THE MOISTURE WITH THIS SYSTEM IS FAIRLY
DEEP AND THAT AREA WILL REMAIN SNOW AND WILL NOT BE IN THE POTENTIAL
DOWNSLOPE AREA.
THOMPSON PASS IS ALSO EXPECTED TO SEE BLIZZARD CONDITIONS AS THE
SOUTHEAST WINDS INCREASE AROUND MIDNIGHT TONIGHT.

SOUTHWEST...THE FRONT WILL BE MOVING QUICKLY THROUGH THE AREA THIS
EVENING AND THEN THINGS WILL SETTLE DOWN A LITTLE SUNDAY AS THE LOW
WEAKENS AND APPROACHES BRISTOL BAY. WINDS WILL SWITCH TO THE NORTH TO
NORTHWEST AS THE LOW PASSES INTO THE GULF OF ALASKA LATE SUNDAY.

ALEUTIANS AND AK PENINSULA...RAIN WILL TURN TO SNOW SHOWERS AS THE
LOW MOVES EASTWARD AND COLD ADVECTION ALONG THE BACK OF THE LOW MOVES
THROUGH THE REGION.

.LONG TERM FORECAST...THE PROGRESSIVE PATTERN WILL CONTINUE THROUGH
THE MIDDLE OF NEXT WEEK AND THEN BECOME A LITTLE MORE SETTLED DOWN AS
A LONG WAVE TROUGH DIGS DOWN OUT OF THE ARCTIC AND SETS UP ALONG THE
WESTERN AND SOUTHWEST ALASKA COAST LATE NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 101 125 131 155 161.
         HEAVY SNOW WARNING 121 145. SNOW ADVISORY 152.
MARINE...GALE 120 130 132 150 155 160 165 170 171 176 179 180.
         STORM 172 175 185. HEAVY FREEZING SPRAY 179.
FIRE WEATHER...NONE.

FEB 12