Small Craft Advisory 891, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT WED OCT 24 2007

.ANALYSIS AND UPPER LEVELS...UPPER LEVEL LOWS CAN BE FOUND OVER THE
WESTERN BERING AND ALONG THE SE ALASKA COAST THIS MORNING. WEAK
RIDGING IS LOCATED OVER KODIAK ISLAND. A WARM FRONT EXTENDING FROM A
LOW IN THE BERING IS STRETCHED E-W ACROSS THE PRIBILOF ISLANDS TO THE
SW COAST.

.MODEL DISCUSSION...MODELS ARE IN GOOD AGREEMENT THROUGH THE FIRST 24
HOURS THEN BEGIN TO DIVERGE WITH THE EVOLUTION OF A BERING SEA LOW
COMPLEX WHICH WILL AFFECT THE WX ACROSS THE STATE. THE LATEST GFS AND
ECMWF ARE IN REASONABLE AGREEMENT THROUGH 96 HOURS THEN MUCH
UNCERTAINTY EXISTS.

.SHORT TERM FORECAST...A LITTLE LIGHT SNOW THIS MORNING ACROSS
SOUTHCENTRAL MOVING INTO THE COPPER RIVER BASIN DUE TO COLD ADVECTION
BEHIND A DEPARTING SHORTWAVE. OVERRUNNING PRECIP ALREADY IN FULL
SWING ALONG THE SW ALASKA COAST AND THIS AREA WILL EXPAND NORTH AND
EAST AS THE DAY PROGRESSES. DECENT AMOUNTS OF RAIN CAN BE EXPECTED
ALONG THE COAST WITH SEVERAL INCHES OF SNOW ACROSS THE KUSKOKWIM
VALLEY AS THE WARM FRONT LIFTS SLOWLY NORTH UNDER A DEEP LAYER OF
COLD AIR TRAPPED IN THE VALLEY. WITH THAT SAID...FZRA IS POSSIBLE FOR
A SHORT TIME AS THE WARMER AIR INITIALLY INVADES THE VALLEY.

AS THE WARM AIR CONTINUES TO SHIFT EAST...EXPECT PRECIP TO BEGIN IN
THE UPSLOPE AREAS OF THE MAT-SU VALLEY LATER THIS AFTERNOON OR
EVENING THEN INTO THE ANCHORAGE BOWL AND PRINCE WILLIAM SOUND AREA
AFTER MIDNIGHT. PRECIP TYPE IS ANOTHER CHALLENGE...WITH WARM
ADVECTION ALOFT, BUT SFC TEMPS BELOW FREEZING. WE THINK THE MAT-SU
VALLEY WILL BE COLD ENOUGH FOR SNOW WITH THE ANCHORAGE BOWL TOO CLOSE
TO CALL AT THIS TIME.

THE LOW IN THE BERING SENDS A MUCH STRONGER FRONT TOWARD THE GULF
EARLY THU WITH WINDS GETTING CRANKED UP ALONG TURNAGAIN ARM AND OTHER
FAVORED WINDY SPOTS. THE MAGNITUDE OF THE WIND IS STILL IN QUESTION
DUE TO UNCERTAINTY WITH THE ORIENTATION OF THE FRONT. ANOTHER SURGE
OF WARM AIR ACCOMPANYING THIS FRONT ALLOWS FOR MAINLY A RAIN EVENT AT
LOWER ELEVATIONS. MEANWHILE...SNOW SHOWERS AND WINDY CONDITIONS WILL
PERSIST ACROSS THE BERING SEA AND INTO SW ALASKA.

.LONG TERM FORECAST...
THE EASTERN BERING LOW IS EXPECTED TO WEAKEN SOMEWHAT FRIDAY
ONWARD...BUT IS EXPECTED TO REMAIN PRESENT THROUGH EARLY NEXT WEEK
WITH LITTLE CHANGE IN THE OVERALL PATTERN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 120 130 132 140 150 155 160 165 170 171 172 176 180
              185 351 352 411 412 414.
FIRE WEATHER...NONE.

JCA