Small Craft Advisory 255, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
145 PM AST THU MAR 24 2005

.DISCUSSION...UPPER LEVEL LOW OVER THE BERING SEA WITH A WEAK RIDGE
OVER EASTERN ALASKA. JET ORIENTED ALONG THE ALEUTIAN RANGE INTO
DENALI WITH AN ASSOCIATED SURFACE FRONT. ANOTHER FEATURE PAIRED WITH
THIS IS A SURFACE LOW OVER BRISTOL BAY SPREADING SHOWERS INTO
SOUTHWEST ALASKA. SOME OF THESE ARE BRIEFLY INTENSE. RAIN AND SNOW
SHOWERS ARE PRESENT WITH THE LOW AND ALONG THIS BOUNDARY. THE
BOUNDARY AND LOW TO SLIP EAST A BIT AS A RIDGE AMPLIFIES IN THE
WESTERN ALEUTIANS. THIS IS DUE TO THE DEVELOPMENT OF AN UPPER LEVEL
AND  SURFACE LOW NEAR KAMCHATKA. THE BOUNDARYS PROGRESSION IS HELD
BACK AS WELL BY A UPPER LEVEL/SURFACE LOW IN THE NORTH PACIFIC MOVING
INTO THE SOUTHERN GULF TONIGHT AMPLIFYING THE RIDGE OVER EASTERN
ALASKA. PRECIP WILL RUN INTO THE SUSITNA VALLEY THOUGH. HAVE
INTRODUCED A SNOW ADVISORY THERE...AS SNOW IS NOT EXPECTED TO END
THERE FOR AWHILE ESPECIALLY WEST OF THE PARKS HIGHWAY. IN
ADDITION...THE JET EXITS INTO CANADA FRIDAY NIGHT WEAKENING THE
BOUNDARY TOMORROW.

AS THE UPPER LEVEL LOW MOVES INTO SOUTHWEST ALASKA FRIDAY
NIGHT...COLD AIR IS PUSHED UP ALONG THE ALEUTIAN RANGE IN SOUTHWEST
ALASKA WITH A BIT FILTERING OVER INTO SOUTH CENTRAL. WITH THE OTHER
UPPER LEVEL LOW MOVING NORTH IN THE GULF...EXPECT THE TWO UPPER LEVEL
LOWS TO SYNC UP WITH A NEGATIVELY TILTED TROUGH DEVELOPING BY
SATURDAY. THE UPPER LEVEL LOW MOVES INTO THE WESTERN GULF SUNDAY. A
SURFACE LOW IS EXPECTED TO MOVE NORTH THROUGH THE GULF SATURDAY AND
INLAND SUNDAY. THE MODELS DIFFER ON THE TIMING AND STRENGTH OF THIS
LOW AT THIS TIME. SO...CONFIDENCE ON THE EXACT SNOWFALL IS LOW.
HOWEVER...IT WILL SNOW THIS WEEKEND OVER MUCH OF SOUTH CENTRAL
ALASKA. THE CONFIDENCE IS HIGH ON THIS SINCE ALL MODELS DO BRING THE
LOW INTO A FAVORABLE LOCATION OVER PRINCE WILLIAM SOUND AT SOME POINT
THIS WEEKEND. IT DOES NOT LOOK LIKE IT WILL STOP SNOWING OVER BRISTOL
BAY AND KUSKOKWIM VALLEY THROUGH THE WEEKEND. EVENTUALLY...THE SNOW
WILL WRAP BACK INTO THE KUSKOKWIM DELTA AROUND THE UPPER LEVEL LOW
SUNDAY. THE UPPER LEVEL LOW

FURTHER WEST A FRONT WILL MOVE THROUGH THE WESTERN ALEUTIAN CHAIN
TONIGHT THEN DISSIPATE OVER THE CENTRAL BERING AND ALEUTIAN CHAIN AS
IT HITS THE RIDGE. ANOTHER...BUT STRONGER...FRONT WILL MOVE INTO THE
WESTERN ALEUTIAN CHAIN FRIDAY NIGHT. THIS FRONT IS ASSOCIATED WITH A
DEVELOPING LOW NEAR THE KAMCHATKA PENINSULA AND BREAK DOWN THE RIDGE
IN THE CENTRAL BERING. A SURFACE LOW WILL DEVELOP ALONG THE FRONT IN
THE CENTRAL ALEUTIANS BY SATURDAY EVENING AND FEED INTO THE UPPER
LEVEL LOW BY SUNDAY. A SERIES OF SHORT WAVE TROUGHS WILL WORK OUT OF
THE KAMCHATKA LOW AND FEED INTO THE UPPER LEVEL LOW OVER SOUTH
CENTRAL INTO EARLY NEXT WEEK.

IN THE EXTENDED...THE WESTERN GULF UPPER LEVEL LOW IS FORCED NORTH AS
THE LOW NEAR THE POLE DROPS INTO THE BERING STRAIT BY MID WEEK. THE
KAMCHATKA LOW AT THIS SAME TIME IS FORCED INTO THIS POLAR LOW AS
ANOTHER LOW RAMPS UP INTO KAMCHATKA. THE POLAR LOW DROPS OVER
SOUTHWEST ALASKA BY THURSDAY WITH A KAMCHATKA LOW. A RIDGE WILL BE
PREVALENT OVER THE CENTRAL BERING SEA. UNSETTLED AND COLD WEATHER
OVER THE INTERIOR MUCH OF THE MAINLAND AS A RESULT. THE ALEUTIAN
CHAIN SHOULD BE COLD OVER THE EAST AND MILD CENTRAL AND WEST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...NONE
FIRE WEATHER...NONE

JN MAR 05