Heavy Freezing Spray Warning 154, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKDT TUE APR 3 2012

.ANALYSIS AND UPPER LEVELS...IN THE UPPER LEVELS THERE IS A RIDGE
OVER SOUTHWEST ALASKA THAT IS KEEPING DRY NORTHWEST FLOW OVER SOUTH
CENTRAL ALASKA. A DEEP TROUGH OVER THE CENTRAL BERING SEA THAT
STRETCHES OVER THE CENTRAL ALEUTIAN ISLANDS IS FEEDING A STRONG LOW
THAT IS BETWEEN ADAK AND ATKA THIS AFTERNOON. THIS UPPER LEVEL TROUGH
WILL CONTINUE TO STRENGTHEN AS THE SURFACE LOW MOVES TO THE SOUTHEAST
INTO WEDNESDAY. ANOTHER UPPER LEVEL RIDGE WILL MOVE INTO THE WESTERN
BERING SEA WEDNESDAY BEHIND THIS LOW.

.MODEL DISCUSSION...MODELS ARE DOING FINE IN THE EASTERN PART OF THE
FORECAST AREA BUT ARE RAPIDLY DIVERGING IN THEIR SOLUTIONS WITH THE
STRONG LOW IN THE CENTRAL ALEUTIANS. AT ISSUE IS THE WAY THE LOW
MOVES TO THE SOUTHEAST AND SPLITS ITS ENERGY. THE ECMWF IS EXPECTED
TO HAVE THE BEST SOLUTION OF THE BUNCH AND HAS BEEN THE MAIN ONE USED
IN THE AFTERNOON PACKAGES. THE ECMWF DROPS THE MAIN LOW TO THE
SOUTHEAST AND DEVELOPS A SECONDARY LOW NEAR BRISTOL BAY WEDNESDAY AND
THEN MOVES THAT ONE RAPIDLY NORTHWARD. THE GFS AND NAM BOTH TRY TO
MEAN OUT THE PRESSURE ALONG THE FRONT AND HAVE LARGE SWINGS IN THE
POSITION OF THE SECONDARY LOW AS A RESULT.

.SHORT TERM FORECAST...CLEAR SKIES IN SOUTH CENTRAL ALASKA WILL GIVE
WAY TO SOME CLOUDS WEDNESDAY MORNING BUT PRECIPITATION WILL BE AROUND
KODIAK ISLAND UNTIL WEDNESDAY NIGHT WHEN IT PUSHES FARTHER EAST
THE BIG ACTION REMAINS IN THE CENTRAL ALEUTIANS AND THE PRIBILOF
ISLANDS AS THE LARGE LOW MOVES THROUGH THOSE AREAS. THE LOW HAS
CAUSED BLIZZARD WARNINGS FOR THE PRIBILOF ISLANDS AND FOR THE CENTRAL
ALEUTIAN ISLANDS. ADAK HAS BEEN EXPERIENCING NEAR ZERO VISIBILITY IN
SNOW AND BLOWING SNOW WITH WIND GUSTING 55 TO 60 MPH MOST OF THE DAY.

WITH THE TRAJECTORY OF THE LOW MOVING MORE TO THE SOUTHEAST IT IS
EXPECTED THAT THE PORTION OF THE CENTRAL ALEUTIANS FROM ATKA EASTWARD
WILL NOT SEE BLIZZARD CONDITIONS DUE TO THE PRECIPITATION DIMINISHING
IN INTENSITY AND THE PRESSURE GRADIENT RELAXING SOME...BUT IT IS
POSSIBLE OVERNIGHT AS THE STORM MOVES THROUGH THE AREA.

.LONG TERM FORECAST...THE RIDGE OF HIGH PRESSURE OVER THE GULF OF
ALASKA WILL SHIFT TO THE EASTERN GULF BY WEDNESDAY ALLOWING THE UPPER
TROUGH ALONG WITH THE SURFACE FRONT WILL BRING RAIN AND SNOW TO THE
COASTAL AREAS BY THURSDAY WITH A CONTINUED CHANCE OF PRECIPITATION
INLAND. A STRONG FRONT WILL CROSS THE BERING PUSHING UP AGAINST THE
SOUTHWEST COAST BY SATURDAY. EXPECT RAIN AND SNOW AHEAD OF THE FRONT
AS IT MOVES ACROSS THE BERING/ALEUTIANS THROUGH MUCH OF THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 187 195.
MARINE...GALE 170 171 175.
         STORM 172 176 179.
FIRE WEATHER...NONE.

APR 12