Gale Warning 620, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AKDT TUE SEP 28 2010

.MODEL DISCUSSION...MODELS ARE VERY CONSISTENT THROUGH THURSDAY AND
THEN BEGIN TO DISAGREE ON THE TIMING OF A STRONG LOW MOVING TOWARD
KODIAK ISLAND. THE MAIN THEME OF A STRONG LOW IS CARRIED ON ALL
MODELS ON ALL RUNS BUT THE ACTUAL TRACK AND TIMING VARIES ENOUGH TO
IMPACT THE FORECAST IN THE GULF REGION LATE THIS WEEK. OTHER THAN
THAT THE MODELS ARE DOING WELL.

.ANALYSIS AND UPPER LEVELS...THERE IS JUST ONE UPPER LEVEL LOW TO
DEAL WITH TODAY...BUT THAT NORMALLY INDICATES A LARGE ONE AND THAT IS
THE CASE. THE UPPER LOW IS CENTERED NORTH OF THE ARCTIC COAST BUT
ENCOMPASSES THE ENTIRE STATE WITH A TROUGH DIGGING SOUTHWARD OVER THE
EASTERN BERING SEA. THE 250 MB JET STREAM IS JUST SOUTH OF THE
FORECAST AREA AS IT MOVES SOUTHEAST OFF THE KAMCHATKA PENINSULA AND
THEN CURVES AROUND SOUTH OF THE ALEUTIAN ISLANDS AND THEN BACK INTO
THE SOUTHEASTERN GULF OF ALASKA. OVER THE NEXT DAY THIS TROUGH WILL
BECOME MORE AMPLIFIED AS IT DIGS SHARPLY SOUTHWARD WITH ITS AXIS
EXTENDING THROUGH THE BERING STRAIT TO THE ALASKA PENINSULA AND THEN
TO AROUND 40N 165W. THE JET STREAM WILL RESPOND BY STRENGTHENING FROM
NORTH TO SOUTH OVER THE CENTRAL AND WESTERN ALEUTIAN ISLANDS.
THE SURFACE LOW IS NOW IN THE VICINITY OF COLD BAY AND WILL MOVE INTO
SOUTHERN SHELIKOF STRAIT BY WEDNESDAY EVENING. THINGS GET A BIT MORE
COMPLICATED AT THIS POINT AS A STRONG SURFACE LOW WILL DEVELOP IN THE
BEND OF THE STRONG JET STREAM SOUTH OF THE FORECAST AREA AND ABSORB
THE LOW IN SHELIKOF STRAIT ON THURSDAY WHILE RAPIDLY STRENGTHENING
AND MOVING INTO THE KODIAK ISLAND AREA FRIDAY.

.SHORT TERM FORECAST...THE ALEUTIAN ISLANDS AND BERING SEA REGION
WILL SEE STRONG WEST TO NORTHWEST WINDS PERSIST AS RAIN SHOWERS
FREQUENT THE AREA. THIS SYSTEM IS WARM ENOUGH THAT THE ALEUTIANS AND
MOST OF THE BERING SEA WILL ONLY SEE RAIN AS THE PRECIPITATION TYPE.
RAIN WILL ALSO BE THE PRECIPITATION TYPE THROUGH BRISTOL BAY THROUGH
TOMORROW. THERE WAS THE THOUGHT THAT THE DILLINGHAM COULD SEE
FREEZING RAIN OVERNIGHT BUT THAT SEEMS UNLIKELY AS SURFACE
TEMPERATURES ARE NOT COLD ENOUGH AND WARMER AIR IS MOVING INTO THE
AREA AT ALL LEVELS. MOST LIKELY SCENARIO IS THAT PRECIPITATION WILL
BE RAINFALL IN WESTERN BRISTOL BAY BEFORE COLDER AIR BEGINS TO MOVE
INTO THE AREA FORM THE NORTHWEST WEDNESDAY EVENING WHEN THE
PRECIPITATION TYPE WILL TURN TO SNOW FROM WESTERN BRISTOL BAY TO THE
NORTHWEST. THE BETHEL AREA IS COLD ENOUGH FOR SNOW BUT WILL LIKELY BE
JUST NORTHWEST OF THE PRECIPITATION AREA. THE KILBUCK MOUNTAINS AND
LOWER KUSKOKWIM VALLEY LOOK TO BE THE AREAS MOST AT RISK FOR SNOWFALL
THROUGH TOMORROW NIGHT.
SOUTH CENTRAL ALASKA WILL SEE PRECIPITATION...MOSTLY RAIN...MOVING IN
FROM THE SOUTH AND SOUTHEAST OVERNIGHT. AREAS ALONG THE EAST SIDE OF
COOK INLET WILL SEE A LOT OF DOWNSLOPE KEEPING THE RAINFALL LIGHT IN
THAT AREA. COPPER RIVER BASIN COULD SEE SOME OVERRUNNING SNOW TONIGHT
BUT IT LOOKS LIKE THE DOWNSLOPE WILL KICK IN THERE AS WELL AND KEEP
MOST OF THE SNOW CONTAINED TO HIGHER ELEVATIONS AND ALONG THE ALASKA
RANGE.

.LONG TERM FORECAST...THE BIG WEATHER STORY FOR LATER IN THE WEEK IS
A VERY STRONG LOW THAT WILL MOVE INTO THE KODIAK TO SOUTHERN COOK
INLET AREA AROUND FRIDAY. THIS LOW WILL ONLY BE 5 TO 10 MILLIBARS
WEAKER THAN THE MASSIVE LOW IN THE SOUTHERN GULF THAT PRODUCED A WIND
STORM IN SOUTH CENTRAL ALASKA LAST FRIDAY INTO SATURDAY. THIS LOW
HOWEVER WILL MOVE NEAR LAND BEFORE IT BEGINS TO WEAKEN AND MIGHT HAVE
MORE WIDESPREAD IMPACT DUE TO THIS TRACK. ALL AREAS OF SOUTHERN
MAINLAND ALASKA AS WELL AS KODIAK ISLAND AND THE AK PENINSULA WILL BE
IMPACTED BY THIS SYSTEM. THIS IS A WARM AIRMASS SO THE PRECIPITATION
TYPE WILL BE RAIN WITH IT EXCEPT FOR HIGHER ELEVATIONS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 120 130 132 140 150 155 160 165 170 171 172 179 180
185.
FIRE WEATHER...NONE.

SEP 10