Small Craft Advisory 1017, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SUN NOV 21 2010

.MODEL DISCUSSION...MODELS ARE DOING WELL AND ARE IN GOOD AGREEMENT
FROM THE 12Z RUNS. OFF HOUR RUNS OF THE NAM HAVE BEEN ACCELERATING
THE PRECIPITATION IN SOUTHWEST AND SOUTH CENTRAL ALASKA BUT THE 00Z
AND 12Z SLOWER SOLUTIONS ARE MORE REASONABLE.

.ANALYSIS AND UPPER LEVELS...A WARM UPPER LEVEL RIDGE OVER THE
WESTERN GULF INTO SOUTH CENTRAL ALASKA WILL SLOWLY MOVE EASTWARD AS
AN UPPER LEVEL TROUGH IN THE BERING SEA BEGINS TO DISPLACE IT.
A SOUTH TO SOUTHWEST JET STREAK IS MOVING OVER SOUTHWEST ALASKA AND
THEN OVER THE TOP OF THIS UPPER LEVEL RIDGE CAUSING ENHANCED
PRECIPITATION IN THIS WARM AIRMASS. INVERSIONS THAT HAVE KEPT SURFACE
TEMPERATURES COLD HAVE DIMINISHED IN SOUTHWEST ALASKA BUT THE THREAT
FOR FREEZING RAIN PERSISTS INLAND TONIGHT.

.SHORT TERM FORECAST...STRONG INVERSIONS FOR AREAS IN SOUTH CENTRAL
ALASKA WILL KEEP THE THREAT OF FREEZING RAIN IN THE AREA FROM LATE
TONIGHT THROUGH AT LEAST NOON TOMORROW. INLAND AREAS IN THE SUSITNA
VALLEY ARE LIKELY TO KEEP SOME FREEZING RAIN THROUGHOUT THE DAY
TOMORROW. IT IS EXPECTED THAT MOST AREAS WILL WARM UP ABOVE FREEZING
BEFORE THE NEXT BATCH OF RAIN MOVES INTO THE AREA TUESDAY.
TEMPERATURES ABOVE THE INVERSION LAYER ARE ARE VERY WARM WITH THE
FREEZING LEVEL WHERE THE TEMPERATURE DROPS BELOW FREEZING AGAIN WAS
OVER 8000 FT IN BOTH ANCHORAGE AND KING SALMON THIS MORNING.

.LONG TERM FORECAST...A LOW WILL MOVE INTO THE WESTERN GULF ON WED
FROM THE BERING SEA WHICH WILL BRING ZONAL FLOW ACROSS MOST OF THE
BERING SEA. BY THURSDAY A 500 MB TROUGH MOVES FROM THE CHUKCHI SEA
INTO THE INTERIOR OF THE STATE. IT APPEARS THAT MOST OF FORECAST AREA
WILL HAVE A CHANCE FOR PRECIPITATION. IT ALSO LOOKS AS IF THAT REGION
WILL BE COOLING BACK TO MORE SEASONABLE TEMPS BY WED OR THURSDAY.
THEREFORE THERE WILL BE SOME SNOW INSTEAD OF RAIN FOR A LARGE PART OF
THE AREA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 160 172 179 180.
FIRE WEATHER...NONE.

NOV 10