Small Craft Advisory 890, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKST FRI NOV 14 2008

.MODEL DISCUSSION...THE MODELS ARE CONSISTENT WITH EACH OTHER TODAY.
THE GFS AND OLD RUN ECMWF MODELS ARE BEING USED FOR OVERALL PATTERN
AND NAM WITH A FEW DETAILS. THE GFS ENSEMBLE FROM THE 12Z RUN SHOWS A
REASONABLE INTERNAL CONSISTENCY IN THE MODEL THROUGH 60 HOURS. BEYOND
84 HOURS IT REALLY BEGINS TO DETERIORATE SO USE GFS WITH CAUTION PAST
84 HOURS.

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL TROUGH OVER THE EASTERN
BERING SEA THAT HAS DOMINATED THE WEATHER PATTERN FOR MUCH OF THIS
WEEK HAS WEAKENED BUT REMAINS IN ROUGHLY THE SAME PLACE. THE 250 MB
JET STREAM IS RATHER WEAK BUT DOES EXTEND AROUND THE SOUTHERN
PERIPHERY OF THIS TROUGH. THIS PATTERN WILL PERSIST UNTIL MONDAY WHEN
AN UPPER LEVEL RIDGE MOVES INTO THE BERING SEA AND PUSHES THE TROUGH
OVER SOUTH CENTRAL ALASKA.

THE LOW IN THE EASTERN GULF OF ALASKA WILL MOVE ON SHORE NEAR YAKUTAT
THIS EVENING. WHILE THIS LOW WAS EXPECTED TO HAVE MINIMAL IMPACT FOR
THE ANCHORAGE FORECAST AREA IT DID PRODUCE A FEATURE THAT HAD A BIT
OF IMPACT ON TODAYS WEATHER. IT PRODUCED A WAVE OFF OF THE MAIN GULF
LOW THAT MOVED AS FAR WEST AS COOK INLET. THIS BROUGHT SNOW INTO THE
PRINCE WILLIAM SOUND AREA AS WELL AS THE EASTERN AND INTERIOR KENAI
PENINSULA AND ANCHORAGE AREAS. THIS DEFORMATION ZONE OVER ANCHORAGE
AND THE INTERIOR OF THE KENAI PENINSULA CAUSED THE MOISTURE THAT WAS
PUSHED OVER THE MOUNTAINS TO BE WRUNG OUT OVER THE REGION. THAT IS
THE REASON THE SNOW PERSISTED LONG AFTER CLOUD TOP TEMPERATURES HAD
WARMED.

IN THE WEST A LOW IN THE WESTERN BERING SEA CONTINUED TO MOVE SLOWLY
SOUTHEASTWARD. THIS LOW IS BECOMING A COMPLEX LOW WITH A TRIPLE POINT
DEVELOPING ALONG THE WEATHER FRONT. THIS TRIPLE POINT WILL BECOME THE
MAIN LOW BY TOMORROW AND WILL MOVE SLOWLY SOUTHEAST...NOT CROSSING
THE ALASKA PENINSULA UNTIL SUNDAY NIGHT.

.SHORT TERM FORECAST...GUSTY OUTFLOW WINDS WILL PERSIST TONIGHT ALONG
THE NORTH GULF COAST AS THE LOW MOVES INTO SOUTHEAST ALASKA. THE
EASTERN COPPER RIVER BASIN WILL SEE SOME SNOW FROM THIS SYSTEM AS IT
MOVES THROUGH TONIGHT BUT AREAS WEST OF THAT WILL ONLY SEE A FEW
ISOLATED SNOW SHOWERS. SNOW WILL DIMINISH AND TURN TO SNOW SHOWERS
THIS EVENING IN THE KUSKOKWIM VALLEY.
THE PRIBILOF ISLANDS WILL ALSO SEE SNOW WITH THE WEAK FRONT MOVING
OVER THEM.

.LONG TERM FORECAST...THERE WILL BE A PATTERN CHANCE EARLY NEXT WEEK
AND AN UPPER LEVEL RIDGE MOVES INTO THE CENTRAL BERING SEA AND
DISPLACES THE TROUGH THAT HAS BEEN IN THAT AREA AND MOVES IT OVER
SOUTH CENTRAL ALASKA. IF THE SURFACE LOW IN THE INTERIOR DEVELOPS
SUFFICIENTLY IT WILL CAUSE A DECREASE IN CLOUDS. THIS WOULD ALLOW
MUCH COLDER TEMPERATURES TO DEVELOP BY THE MIDDLE OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 170 172 175 176 185.
FIRE WEATHER...NONE.

NOV 08