Small Craft Advisory 1024, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKST THU DEC 17 2009

.MODEL DISCUSSION...THE NAM MODEL WAS BY FAR THE BEST FOR THE LAST
SNOWFALL AROUND SOUTH CENTRAL ESPECIALLY IN THE COOK INLET REGION
WHERE IT WAS THE ONLY MAJOR MODEL TO DETECT THAT MESO LOW AS WELL AS
HAVING THE SHORT WAVE THAT DROPPED MORE SNOW OVER ANCHORAGE AND THE
MAT-SU VALLEY LAST NIGHT. THE NAM SHOULD REMAIN THE BEST ONE FOR THE
NEXT FEW DAYS IN THE SOUTH CENTRAL REGION AND AROUND THE NORTHERN
GULF.
ALL THE MODELS ARE DOING FINE OUT WEST IN THE SHORT TERM BUT THE
LARGE AND COMPLEX LOW THAT IS MOVING INTO THE WESTERN ALEUTIANS IS A
MESS WITH ALL THE MODELS. THE NAM IS TOO FAR WEST INITIALLY AND THE
ECMWF FAILS TO DEVELOP THE SECONDARY LOW THAT WILL MOVE INTO THE
CENTRAL ALEUTIANS FRI NIGHT. THE GFS IS PROBABLY THE BEST BET AT THIS
TIME. WHILE IT HAS NOT BEEN TERRIBLY STABLE IN RUN TO RUN CONSISTENCY
IT HAS SETTLED DOWN THE LAST TWO RUNS AND LOOKS TO BE THE BEST MODEL
TO START WITH.

.ANALYSIS AND UPPER LEVELS...THE COLD UPPER LEVEL LOW IS CENTERED
OVER THE LOWER KUSKOKWIM VALLEY THIS AFTERNOON. THIS IS BRINGING DUE
SOUTH UPPER LEVEL FLOW TO PRINCE WILLIAM SOUND AND EASTWARD WHILE
COLD NORTH TO NORTHWEST FLOW REMAINS OVER SOUTHWEST ALASKA.
AT THE SURFACE THE LOW THAT WAS IN PRINCE WILLIAM SOUND HAS BECOME
VERY DIFFUSE WITH AN APPARENT CENTER SOUTHEAST OF SEAWARD AND THE
MESO LOW REMAINING IN COOK INLET. THE MESO LOW IN COOK INLET WILL
REMAIN AND SLOWLY DISSIPATE THROUGH FRIDAY.

A STRONG JET STREAM IS REMAINING WELL SOUTH OF THE AREA BUT IS
FEEDING THE LOW THAT IS MOVING INTO THE WESTERN ALEUTIANS. IT WILL
ALSO CAUSE A TRIPLE POINT LOW TO DEVELOP AND MOVE INTO THE CENTRAL
ALEUTIANS ON SATURDAY...WHICH WILL BECOME THE DOMINANT LOW AND MAIN
WEATHER FEATURE BY THEN.

.SHORT TERM FORECAST...THE SOUTHWEST ALASKA REGION WILL REMAIN COLD
AND BREEZY WHILE THAT VERY COLD AIR SPILLS INTO SOUTH CENTRAL ALASKA.

SNOWFALL SHOULD BE TAPERING OFF OVER SOUTH CENTRAL ALASKA EXCEPT FOR
THE COPPER RIVER BASIN WHICH WILL STILL SEE SOME OVER RUNNING
OVERNIGHT.
SNOW BANDS SIMILAR TO LAKE EFFECT SNOW CAN BE SEEN CIRCULATING INTO
THE MESO LOW IN COOK INLET WHICH HAS BECOME A MORE SIGNIFICANT
FEATURE THAN NORMAL.

.LONG TERM FORECAST...AS THE LOW IN THE CENTRAL ALEUTIANS THIS
WEEKEND MOVES INTO THE BERING SEA AN UPPER LEVEL RIDGE WILL BEGIN TO
BUILD OVER SOUTH CENTRAL ALASKA AND EASTWARD. THIS WILL RESULT IN
WIDESPREAD SOUTHERLY WINDS AND A RETURN TO WARMER TEMPERATURES ACROSS
THE SOUTHERN PART OF THE STATE. THE WEATHER WILL REMAIN STORMY IN THE
ALEUTIAN ISLANDS THROUGH THE WEEKEND AS A SERIES OF LOWS PROGRESS
THROUGH THE REGION. BY EARLY NEXT WEEK A CHINOOK IS POSSIBLE IN SOUTH
CENTRAL ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 125 130 132 150 155 170 172 185
 STORM 175 176
 HEAVY FREEZING SPRAY 121 129 130 132 138 140 141 150 155 160 180 185
FIRE WEATHER...NONE.

DEC 09