Snow Advisory 15, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM ADT SAT APR 5 2008

.MODEL DISCUSSION...MODELS ARE IN AGREEMENT IN THE OVERALL PATTERN
AND DEVELOPMENT OF LOWS. THERE IS STILL SOME DISAGREEMENT WITH THE
LOW NEAR PRINCE WILLIAM SOUND. NAM MAY HAVE THE BEST SOLUTION FOR THE
SHORT TERM SINCE IT HAS BEEN MORE CONSISTENT WITH THE LOW POSITION
AND THIS MAY BE DUE TO ITS HIGHER GRID RESOLUTION. LONGER TERM THE
GFS SOLUTION LOOKS A BIT BETTER THAN NAM OF ECMWF BUT THE PATTERN
WILL BE PROGRESSIVE ENOUGH THAT THIS MAY CHANGE AS WELL SINCE IT IS A
DIFFICULT SITUATION FOR MODELS TO ACCURATELY RESOLVE.

.ANALYSIS AND UPPER LEVELS...A COLD UPPER LEVEL LOW IS CENTERED OVER
THE BERING STRAIT WITH AN ELONGATED TROUGH EXTENDING SOUTHEAST OVER
THE SOUTHERN COOK INLET AREA AND INTO THE CENTRAL GULF OF ALASKA.
THIS ELONGATION IS SIGNIFICANT SINCE MODELS ALL HAVE A CUT OFF LOW
DEVELOPING SOUTH SOUTHEAST OF THE KENAI PENINSULA OVERNIGHT AND THEN
MOVING TO THE NORTHERN PANHANDLE BY SUNDAY NIGHT. THE MAIN UPPER
LEVEL LOW WILL REMAIN NEARLY STATIONARY THROUGH MONDAY.

THE WEAK SURFACE LOW IN SOUTHERN PRINCE WILLIAM SOUND IS PUSHING
MOISTURE INTO THE NORTH GULF COAST AS WELL AS INTO THE ANCHORAGE AREA
AND NORTHWARD. THE COLD AIR ADVECTION FROM THE SOUTHWEST IN
ASSOCIATION WITH THE COLD FRONT THAT WENT THROUGH THE COOK INLET AREA
EARLY THIS MORNING IS CAUSING TEMPERATURES TO SLOWLY DROP THROUGH THE
DAY. IT IS ALSO CAUSING THE MOISTURE TO PRECIPITATE OUT OVER
ANCHORAGE AND AREAS NORTH.

.SHORT TERM FORECAST...
THE BACK EDGE OF THE MOISTURE PASSED THROUGH HOMER EARLY THIS MORNING
AND THROUGH KENAI AROUND NOON. THIS MOVEMENT WILL STALL SOUTHWEST OF
FIRE ISLAND AND REMAIN THERE THROUGH THE NIGHT. THE MAJORITY OF
SNOWFALL IN THE ANCHORAGE TO MAT-SU VALLEY AREA WILL BE THROUGH THE
EVENING. AFTER THIS THE UPPER LEVEL SUPPORT DIMINISHES AS THE 500 MB
CUT OF LOW DEVELOPS AND MOVES SOUTHEAST.

PRECIPITATION IN THE EASTERN PRINCE WILLIAM SOUND AREA WILL CHANGE TO
ALL SNOW THIS EVENING AS THE COLD ADVECTION REACHES THOSE AREAS.

HIGH PRESSURE IN THE CENTRAL BERING SEA WILL MOVE INTO SOUTHWEST
ALASKA OVERNIGHT AND INCREASE THE POSSIBILITY OF FOG DEVELOPING.

.LONG TERM FORECAST...THE UPPER LEVEL LOW IS EXPECTED TO REMAIN OVER
THE CHUKCHI SEA INTO THE MIDDLE OF NEXT WEEK. OTHER THAN THAT THE
CONFIDENCE IN THE MODELS IS VERY LOW FROM THE MIDDLE TO LATE PART OF
NEXT WEEK SO THERE ARE NO SIGNIFICANT CHANGES IN LONG TERM FORECASTS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 120 130 132.
         HEAVY FREEZING SPRAY 130 132 138 150.
FIRE WEATHER...NONE.

APR 08