Blizzard in Alaska, November 29, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
115 PM AKST TUE NOV 29 2011

.ANALYSIS AND UPPER LEVELS...A PROGRESSIVE PATTERN CONTINUES ACROSS
THE ALASKA FORECAST REGION AS A POTENT JET STREAM INTENSIFIES AND
MOVES SYSTEMS ACROSS THE NORTH PACIFIC AND BERING. THE MAIN FOCUS OF
TODAY'S FORECAST IS AN OCCLUDED LOW PRESSURE SYSTEM THAT IS
CURRENTLY LOCATED OVER UNALASKA ISLAND. WHILE THIS LOW HAS ALREADY
REACHED ITS PEAK INTENSITY OF 968 MB THIS MORNING...IT WILL IMPACT
MUCH OF THE FORECAST AREA OVER THE NEXT 30 HOURS. THIS SYSTEM WILL
TRACK INLAND ACROSS BRISTOL BAY TODAY AND REACH THE KUSKOKWIM DELTA
AT 995 MB BY WEDNESDAY EVENING. ITS ASSOCIATED FRONT ALREADY
STRETCHES ACROSS THE ALASKA PENINSULA AND KUSKOKWIM DELTA AND IS
SUPPORTING SNOW ACROSS THE SOUTHWEST MAINLAND. THIS FRONT WILL
REMAIN RELATIVELY STRONG AND CONTINUE TO PROGRESS EASTWARD OVER THE
NEXT 30 HOURS...BRINGING SNOW AND GUSTY WINDS TO THE SOUTHCENTRAL
ZONES.

.MODEL DISCUSSION...MODELS ARE NOW IN EXCELLENT AGREEMENT IN BOTH
THE TRACK AND INTENSITY OF THE LOW PRESSURE SYSTEM TRACKING FROM THE
NORTH PACIFIC INTO THE BERING. HOWEVER...THE MODELS ARE SHOWING MORE
DISCREPANCIES IN THE TEMPERATURE AND PRECIPITATION ACROSS THE
REGION...WITH THE HIGH RESOLUTION NAM CAPTURING GAP WINDS MORE
ACCURATELY...AND THE GFS PICKING UP ON MORE SUBTLE PRECIPITATION
PROCESSES. THEREFORE A BLEND OF THE NAM AND GFS WAS USED FOR THE
SHORT TERM FORECAST.

.SHORT TERM FORECAST...

.SOUTHCENTRAL ALASKA...
AN APPROACHING FRONT WILL BRING PRECIPITATION AND GUSTY GAP WINDS
ACROSS MUCH OF THE SOUTHCENTRAL REGION BEGINNING IN KODIAK ISLAND
AND SOUTHERN KENAI PENINSULA BY THIS AFTERNOON. WITH MORE SOUTHERLY
WINDS ALOFT...DOWNSLOPING IS NOT EXPECTED TO BE AS SIGNIFICANT WITH
THIS EVENT AND MORE WIDESPREAD SNOW IS EXPECTED. PRECIPITATION TYPE
REMAINS A CHALLENGING PROBLEM FOR THIS FORECAST.  WHILE THIS SYSTEM
WILL TRANSPORT A SIGNIFICANT AMOUNT OF WARM AIR NORTHWARD...COLD AIR
WILL REMAIN IN PLACE. FOR THE BULK OF THE EVENT...PRECIPITATION IS
EXPECTED TO REMAIN SNOW WITH UP TO ONE INCH POSSIBLE ACROSS THE
ANCHORAGE BOWL AND MATANUSKA VALLEY. HOWEVER...WITH WARM
TEMPERATURES ALOFT...LIGHT FREEZING RAIN MAY MIX IN WITH SNOW AT
TIMES.

SEVERAL INCHES OF SNOW ARE EXPECTED TO FALL ALONG THE ALASKA RANGE
THROUGH BOTH THE COPPER RIVER BASIN AND SUSITNA VALLEY. SNOW WILL
BEGIN THIS EVENING ACROSS THE WESTERN SUSITNA VALLEY AND REACH THE
WRANGELL MOUNTAINS BY LATE TONIGHT. STEADY SNOW IS ALSO EXPECTED
ALONG THE EASTERN KENAI PENINSULA...WHERE COOLER INLAND AIR WILL
KEEP SNOW FALLING FROM THIS AFTERNOON THROUGH TONIGHT. THE HEAVIEST
SNOW TOTALS FOR THIS WEATHER SYSTEM WILL BE ACROSS THE VALDEZ AREA
WHERE OVER TWO FEET OF SNOW IS POSSIBLE.

THIS SYSTEM WILL ALSO SUPPORT STRONG WINDS AND BLIZZARD CONDITIONS
THROUGH SEVERAL GAPS ACROSS THE REGION. BLIZZARD CONDITIONS ARE
EXPECTED THROUGH PORTAGE VALLEY BY THIS EVENING THROUGH TONIGHT. FOR
 THOMPSON PASS...BLIZZARD CONDITIONS WILL START BY MIDNIGHT TONIGHT
AND CONTINUE THROUGH WEDNESDAY MORNING. MEANWHILE...WIND GUSTS UP TO
70 MPH ARE POSSIBLE THROUGH WEST TURNAGAIN ARM THIS EVENING.

LIGHT SNOW WILL CONTINUE TO BE A POSSIBILITY ACROSS THE SOUTHCENTRAL
ZONE INTO THURSDAY AS A WEAK UPPER LEVEL SHORTWAVE PROGRESSES
THROUGH BEHIND THE MAIN FRONT.

.SOUTHWEST ALASKA...A 974 MB LOW NEAR UNALASKA ISLAND AND ITS
ASSOCIATED FRONT ARE BRINGING SNOW AND GUSTY WINDS TO THE SOUTHWEST
MAINLAND. BLIZZARD CONDITIONS ARE EXPECTED TO OCCUR ON THE NORTH
SIDE OF THE LOW ACROSS THE KUSKOKWIM DELTA WHERE COLD AIR IS ALREADY
IN PLACE. PRECIPITATION WILL BE MIXED ACROSS THE BRISTOL BAY
ZONE...WITH TEMPERATURES ALREADY ABOVE FREEZING ACROSS MUCH OF THE
AKPEN. HOWEVER...BLIZZARD CONDITIONS ARE EXPECTED TO CONTINUE
THROUGH THE AREA NORTH AND WEST OF KING SALMON WHERE COLD AIR WILL
MAINTAIN ITS HOLD AS THE FRONT PROGRESSES THROUGH.  A MIXED BAG OF
PRECIPITATION WILL IMPACT THE REST OF THE ZONE AS WARM AIR
PROGRESSES INLAND THROUGH THE AFTERNOON AND EVENING HOURS.

BERING SEA/ALEUTIANS....A STRONG LOW PRESSURE SYSTEM OVER UNALASKA
ISLAND HAS BEEN BRINGING RAIN AND SOME GUSTY WINDS ACROSS THE
EASTERN ALEUTIANS. THE NEXT SYSTEM IS FOLLOWING QUICKLY ON THE HEELS
OF THIS LOW...WITH A FRONT APPROACHING THE WESTERN ALEUTIANS BY
TONIGHT...AND REACHING THE EASTERN ALEUTIANS BY WEDNESDAY NIGHT.

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

ELN NOV 11