Gale Warning 294, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AKDT TUE MAR 30 2010

UPDATED FOR NEW BLIZZARD WARNING ZONE 181

.ANALYSIS AND UPPER LEVELS...AN UPPER LEVEL TROUGH REGION CONTINUES
TO DOMINATE A REGION STRETCHING FROM THE BEAUFORT SEA TO THE WESTERN
NORTH PACIFIC. AN UPPER LEVEL LOW PRESSURE THAT COVERS MUCH OF THE
BERING IS CENTERED NORTH OF KAMCHATKA PENINSULA AND IS SLOWLY MOVING
TO THE SOUTHEAST. A SMALLER AND WEAKER LOW IS CENTERED OVER THE
BEAUFORT SEA WHILE A BROAD WEAK LOW SITS OVER THE GULF OF ALASKA. AN
EXTENSIVE UPPER LEVEL RIDGE SPANS FROM THE CENTRAL ALEUTIANS TO THE
WESTERN ALASKA PENINSULA. A POWERFUL 180 KT UPPER LEVEL JET IS
LOCATED ALONG THE WESTERN BOUNDARY OF THIS RIDGE WHILE A 160 KT JET
IS STRENGTHENING ALONG THE EASTERN EDGE OF THE RIDGE.

AT THE SURFACE...A 975 MB LOW IS CURRENTLY 200 MILES SOUTH OF
MIDDLETON ISLAND. ALTHOUGH IT IS WITHIN PROXIMITY OF THE 160 KT JET
ALONG THE EASTERN SIDE OF THE UPPER LEVEL RIDGE...IT IS LOCATED
WITHIN THE LEFT ENTRANCE REGION OF THE JET WHERE LOWS WEAKEN DUE TO
SINKING AIR. IN CONTRAST... A POTENT 968 MB LOW 450 MILES SOUTH OF
SHEMYA IS LOCATED WITHIN THE LEFT EXIT REGION OF THE WESTERN JET
WHERE STRONG VERTICAL MOTION IS SUPPORTED.  AS A RESULT THIS LOW WILL
CONTINUE TO DEVELOP THROUGH TOMORROW AND MOVE TO THE NORTHEAST
RELATIVELY QUICKLY. A FRONT EXTENDS TO THE SOUTHEAST FROM THE STRONG
LOW SOUTH OF SHEMYA.

.MODEL DISCUSSION...MODELS ARE CURRENTLY IN GENERAL AGREEMENT ON THE
DISSIPATION OF THE GULF LOW AND PROGRESSION EASTWARD OF THE ALEUTIAN
LOW IN THE SHORT TERM.  HOWEVER...THE NAM IN PARTICULAR WAS TOO MOIST
THIS MORNING AND WAS DEPICTING PRECIPITATION OVER THE ANCHORAGE BOWL
REGION WHERE ONLY PARTLY CLOUDY CONDITIONS EXISTED. THEREFORE...THE
FORECAST WAS ADJUSTED FOR DRIER CONDITIONS AND LOWER PRECIPITATION
AMOUNTS FOR THE SHORT TERM IN THE SOUTHCENTRAL REGION. THE ECMWF WAS
USED FOR THE LONG TERM.

.SHORT TERM FORECAST...
SOUTH-CENTRAL ALASKA...AN UPPER LEVEL SHORT WAVE ASSOCIATED WITH THE
KAMCHATKA LOW WILL BRING THE POSSIBILITY OF RAIN AND SNOW SHOWERS TO
SOUTHCENTRAL TONIGHT AND TOMORROW. MODELS INDICATE ONLY ISOLATED
SHOWERS TODAY BUT A GREATER CHANCE FOR RAIN AND SNOW SHOWERS TOMORROW
WITHIN THE SUSITNA VALLEY. ALTHOUGH THERE IS UPPER LEVEL
SUPPORT...THE AIR WILL REMAIN TOO DRY OVER THE ANCHORAGE AREA FOR
STEADY PRECIPITATION. THE COPPER RIVER BASIN IS EXPECTED TO REMAIN
RELATIVELY DRY AS WELL...WITH RELATIVELY QUIET WEATHER OVER THE NEXT
FEW DAYS.

SOUTHWEST ALASKA...THE ISOLATED SNOW SHOWERS THAT HAVE IMPACTED THE
EASTERN PORTION OF THE ZONE TODAY IN LOCATIONS SUCH AS STONEY WILL
SLOWLY TAPER OFF THROUGH THE EVENING AS THE UPPER LEVEL SHORTWAVE
PROGRESSES EASTWARD. MEANWHILE...ISOLATED SNOW SHOWERS ARE STILL A
POSSIBILITY ALONG THE NORTHERN BERING COAST OF THE ALASKA PENINSULA
AS COOLER AIR MOVES OFF THE ICE AND OVER THE OPEN SEA. HOWEVER...THIS
SNOW SHOULD TAPER OFF BY TONIGHT AS THE WIND DIRECTION CHANGES TO THE
SOUTHEAST AHEAD OF THE APPROACHING SHEMYA LOW.

BERING SEA AND ALEUTIANS...BLIZZARD CONDITIONS ARE POSSIBLE TODAY AND
INTO TOMORROW ACROSS THE CENTRAL ALEUTIANS AND THEN THE ALASKA
PENINSULA AND THE PRIBILOF ISLANDS TONIGHT INTO TOMORROW AFTERNOON.
AS A POTENT LOW PRESSURE MOVES RAPIDLY TO THE NORTHEAST...IT WILL
PRODUCE STRONG WINDS AND SNOW AHEAD OF THE LOW. STORM FORCE WINDS ARE
A POSSIBILITY ACROSS THE CENTRAL AND EASTERN ALEUTIAN ISLANDS.

.LONG TERM FORECAST...MODELS CONTINUE TO INDICATE AN UPPER LEVEL
TROUGH REGION ACROSS THE BERING AND THE GULF WITH THE UPPER LEVEL JET
IN CLOSE PROXIMITY.  AS A RESULT...THE PATTERN WILL REMAIN ACTIVE
OVER THE NEXT WEEK WITH MULTIPLE LOWS MOVING ACROSS THE REGION.
THERE IS NO HINT OF A STRONG WARM UP IN THE NEAR FUTURE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...181 187 195
MARINE...STORM 155 170
         GALE 120 130 132 138 150 160 165 171 172 175 179
         HEAVY FREEZING SPRAY...130 138 150
FIRE WEATHER...NONE.

ELN MAR 10