Blizzard in Alaska, April 12 to 13, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT TUE APR 12 2011

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT...ESPECIALLY IN THE SHORT TERM. THE GFS
WAS MOSTLY USED WITH THIS PARTICULAR FORECAST PACKAGE FOR BOTH
DOMAINS. THE EC AND NAM DO SHOW GOOD AGREEMENT WITH AN EASTERLY WAVE
MOVING ACROSS THE NORTHERN GULF AND COASTAL LOCATIONS.

.ANALYSIS AND UPPER LEVELS...

A LARGE COMPLEX TROUGH ALOFT EXTENDS FROM THE CHUKCHI SEA SOUTH TO
THE GULF OF ALASKA. THIS LARGE AREA WITHIN THE TROUGH IS MOSTLY
SEEING WEAK DISTURBANCES IN WEAK FLOW. A STRENGTHENING RIDGE OVER THE
CENTRAL AND WESTERN BERING SEA IS HELPING TO INCREASE THE HEIGHT
GRADIENT IN NORTHERLY FLOW FROM FAR EASTERN RUSSIA SOUTHEAST TO THE
NORTH PACIFIC TO THE SOUTH OF THE ALASKA PENINSULA. A POTENT
NORTHERLY JET STREAK WILL CONTINUE TO STRENGTHEN AS THIS RIDGE OF
HIGH PRESSURE MOVES NORTH AND STRENGTHENS OVER THE NEXT COUPLE OF
DAYS. A VERY SMALL AND POTENT DISTURBANCE HAS JUST MOVED OVER THE
ALASKA PENINSULA IN THE LAST COUPLE OF HOURS AND BROUGHT A BRIEF
PERIOD OF HEAVY SNOW...BUT BLIZZARD CONDITIONS FAILED TO MATERIALIZE
THERE.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

COMPLEX YET WEAK LOW IN THE GULF WILL KEEP SCATTERED SHOWERS CONFINED
TO THAT REGION AS WELL AS COASTAL LOCATIONS. VERY LOW HEIGHTS ALOFT
MEAN CONVECTIVE ACTIVITY AGAIN POSSIBLE MAINLY OVER THE HIGHER
TERRAIN WITH AFTERNOON DAYTIME HEATING FROM THE SUN...BUT THIS
ACTIVITY SHOULD BE ISOLATED. A DISTURBANCE OVER NORTHWEST CANADA WILL
ROTATE SOUTH AND WEST TO THE NORTH AND WEST OF THE ALASKA RANGE...BUT

WILL HAVE LITTLE EFFECT ON THE SOUTHCENTRAL REGION. AN EASTERLY WAVE
FORMS OVER THE EASTERN GULF TODAY AND ROTATES WEST THROUGH WEDNESDAY
NIGHT...AND WILL BRING ANOTHER PERIOD OF SHOWERS ALONG THE NORTHERN
GULF COAST OVER TO THE KENAI PENINSULA THURSDAY.

SOUTHWEST...

A FEW SNOW SHOWERS WILL SPILL OVER INTO THE EASTERN BRISTOL BAY ZONE
TODAY. NORTHERLY WINDS WILL REMAIN STRONG ALONG THE KUSKOKWIM DELTA
COAST THROUGH TONIGHT...WITH SCATTERED LIGHT SNOW SHOWERS THROUGH
EARLY AFTERNOON AND BLOWING SNOW REDUCING VISIBILITIES TO NEAR ONE
MILE AT TIMES THROUGH TONIGHT. OTHERWISE...TRANQUIL CONDITIONS
EXPECTED OVER THE NEXT FEW DAYS WITH DRY DISTURBANCES MOVING THROUGH
IN NORTH TO NORTHEAST FLOW ALOFT.

BERING SEA/ALEUTIANS...

COLD ADVECTION SNOW SHOWERS AND STRONG WINDS WILL CONTINUE THROUGH
THIS AFTERNOON OVER THE BERING AND THROUGH AT LEAST TONIGHT ALONG THE
BERING SIDE OF THE ALASKA PENINSULA. FOG WILL BECOME MORE PREVALENT
OVER THE WESTERN BERING WITH A STEEP INVERSION JUST ABOVE THE
SURFACE. THE RIDGE WILL CONTINUE TO STRENGTHEN OVER THE NEXT FEW DAYS
OVER THE WEST CENTRAL BERING...AND WILL EVENTUALLY BECOME A CUT-OFF
HIGH OVER FAR NORTHEAST RUSSIA BY LATE WEEK. THIS WILL ALLOW FOR
EASTERLY WAVES FROM THE MAINLAND REGION MOVE SOUTH AND WEST OVER THE
SOUTHERN BERING AND NORTHERN PACIFIC TOWARDS LATE WEEK INTO EARLY
NEXT WEEK.

.LONG TERM FORECAST...

FAIRLY TRANQUIL AND SPRING LIKE PATTERN FOR THE MAINLAND WITH
EASTERLY WAVES MOVING FROM THE MAINLAND SOUTH AND WEST OVER THE
BERING ON THE SOUTH AND EAST SIDE OF THE STRONG CUT-OFF HIGH OVER
NORTHEAST RUSSIA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES...150 155 160 165 170 175
         HVY FRZG SPRY...150 155 160 165 179
FIRE WEATHER...NONE.

CC APR 11