Small Craft Advisory 449, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTH CENTRAL AND SOUTHWEST ALASKA
500 PM ADT SUN MAY 20 2007

.ANALYSIS AND UPPER LEVELS...
THE TWO MAIN FEATURES ARE THE THERMALLY INDUCED SURFACE TROUGH ACROSS
THE INTERIOR AND THE BROAD RIDGE OF HIGH PRESSURE FROM THE GULF OF
ALASKA TO THE SURFACE HIGH NEAR ST MATTHEW ISLAND.

IN THE UPPER LEVELS WE HAVE A WEAK LOW OVER THE BRISTOL BAY COAST
THAT SHOULD SLOWLY DRIFT NORTHWEST THROUGH MON AFTERNOON. THE UPPER
TROUGH WILL ROTATE NORTH ACROSS KODIAK ISLAND TONIGHT THEN EXTEND
FROM THE KUSKOKWIM DELTA SOUTHEAST TO THE NORTH GULF COAST MONDAY.
WE ALSO HAVE A LOW WELL SOUTH OF THE ALEUTIANS IN THE NORTH PACIFIC.
THE COLD UPPER LEVEL AIR OVER THE MAINLAND COUPLED WITH LOW LEVEL
WARMTH AND MOISTURE WILL KEEP CONDITIONS UNSTABLE TODAY AND MON.

.MODEL DISCUSSION...
MODELS HAVE HAD GOOD RUN TO RUN CONSISTENCY AND ARE IN GENERALLY GOOD
AGREEMENT. THE MEAN SURFACE LOW PRESSURE OVER THE MAINLAND IS HANDLED
SIMILARLY BY ALL MODELS AND THE INCOMING LOW AND FRONT AND THE MEAN
TROUGH OF THIS SYSTEM IS ALSO HANDLED WELL, THOUGH THE NAM IS
SLIGHTLY SLOWER MOVING THE MEAN TROUGH NORTH THAN THE GFS AND UKMET.
THE CURRENT FORECAST SOLUTIONS WILL REFLECT THE GFS.

.SHORT TERM FORECAST...
THE UPPER LEVEL COLD AIR AND LOW LEVEL WARMTH AND MOISTURE WILL KEEP
CONDITIONS UNSTABLE OVER THE SOUTH CENTRAL AREA TO THE KUSKOKWIM
VALLEY THIS EVENING AND AGAIN MONDAY. THE HIGH PRESSURE OVER THE
BERING WILL HOLD THE LOW CLOUDS AND FOG OVER THAT REGION UNTIL THE
NORTH PACIFIC LOW PUSHES NORTH AND THE ASSOCIATED EAST TO NORTHEAST
GRADIENT SPREADS TO THE ALASKA PENINSULA AND EASTERN ALEUTIANS THAT
SHOULD MIX OUT THE LOW LEVEL CLOUDS AND FOG LATE MON. SINCE THE
NORTHWARD AND EASTWARD MOVEMENT OF THE NORTH PACIFIC LOW AND
ASSOCIATED FRONT IS SLOWER THAN PREVIOUSLY EXPECTED WE ARE BACKING
OFF ON THE BEGINNING OF RAIN FOR THE EASTERN ALEUTIANS ALASKA
PENINSULA AND KODIAK ISLAND.

THE UPPER TROUGH OVER THE BRISTOL BAY COAST WILL KEEP THE THREAT OF
SHOWERS GOING FOR THE BRISTOL BAY AND KUSKOKWIM DELTA AREAS THROUGH
MONDAY.

.LONG TERM FORECAST...
WEDNESDAY WE EXPECT AN INFLUX OF WARMER AIR ALOFT THAT WILL RESULT IN
MORE STABLE CONDITIONS OVER THE SOUTHERN MAINLAND WED. WE EXPECT THE
PATTERN TO SEE A SIGNIFICANT SHIFT BEGINNING SUN AS AN UPPER LEVEL
LOW OVER THE ARCTIC HAS A TROUGH EXTENDING SOUTH TO ANOTHER UPPER LOW
CENTERED OVER THE CENTRAL TO EASTERN ALEUTIANS. THE UPPER LEVEL
TROUGH IS EXPECTED TO EXTEND FROM THE ARCTIC OVER WESTERN ALASKA
WITH THE COLDER AIR ALOFT MOVING BACK OVER THE MAINLAND. AS FOR THE
CHANGES TO THE WEATHER EXPECTED WITH THIS PATTERN CHANGE. THE MAIN
CHANGE WILL BE INCREASED CHANCE FOR RAIN ALONG MOST OF THE COASTAL
AREAS AND A RETURN TO CLOUDIER AND COOLER CONDITIONS NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...RED FLAG ZONE 111.

SAM MAY 07