Gale Warning 639, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM ADT THU SEP 13 2007

.MODEL DISCUSSION...THERE ARE A FEW MORE PROBLEMS WITH THE MODELS
TODAY AS COMPARED WITH YESTERDAY WHEN THEY LOOKED TO BE PERFORMING
VERY WELL. THE FIRST ISSUE IS AN IMMEDIATE IMPACT ON THE FORECAST
RELATING TO AN UPPER LEVEL WAVE THAT HAS DEVELOPED SOUTH OF KODIAK
ISLAND LATE LAST NIGHT AND IS HEADING TOWARD COOK INLET. THE ONLY
MODEL THAT HAS A HINT AT THIS FEATURE IS THE NAM FROM THE 12Z RUN.
THE WAVE CAN BE DISCERNED IN THE 500 MB LEVEL IN THE VORTICITY AND
TEMPERATURE FIELDS. THE GFS HAS ALMOST NO INDICATION OF THE EXISTENCE
OF THIS WAVE. THIS WILL AFFECT THE WEATHER IN SOUTH CENTRAL ALASKA
OVERNIGHT AS IT MOVES THROUGH THE AREA.
THE OTHER BIG QUESTION WITH THE MODELS DEALS WITH THE LOW THAT IS
DEVELOPING SOUTH OF SAND POINT AND WILL MOVE INTO THE GULF OF ALASKA
THIS WEEKEND. THE BIG PICTURE ON THIS SYSTEM REMAINS FAIRLY
CONSISTENT WHICH IS GOOD. THE ISSUE IS THE STRENGTH OF THE SYSTEM AND
THE EXACT POSITIONING. THE GFS 12Z RUN WEAKENED THE LOW AND MOVED IT
FARTHER EAST THAN ANY OF THE PREVIOUS RUNS. THE NAM DID NOT DO THIS.
THE GFS ENSEMBLE SHOWS THAT THE MODEL IS STRUGGLING A BIT WITH THE
POSITIONING OF THIS LOW IN THE GULF. THIS LOOKS LIKE A SITUATION
WHERE THE NAM MAY HAVE A BETTER SOLUTION FOR HOW THIS STORM PLAYS OUT
IN THE GULF AND ALONG THE GULF COAST.

.ANALYSIS AND UPPER LEVELS...AS MENTIONED IN THE PREVIOUS SECTION
THERE IS A POTENT UPPER LEVEL WAVE THAT IS SOUTH OF KODIAK ISLAND
MOVING NORTHWARD. THIS WAVE SHOWS UP VERY WELL ON THE IR AND WATER
VAPOR SATELLITE. IT LOOKS TO HEAD INTO COOK INLET THIS EVENING AND
INTO THE SUSITNA VALLEY AFTER THAT. THE LOW THAT WILL MOVE INTO THE
GULF OF ALASKA THIS WEEKEND IS BEGINNING TO ORGANIZE NEAR 45N 155W.
THIS IS ALSO VISIBLE ON IR SATELLITE.
IN THE BERING SEA THE LOW CONTINUES TO CHURN NEAR THE BERING STRAIT
AND WILL SLOWLY WEAKEN OVER THE NEXT DAY OR TWO. A MODERATELY TIGHT
SOUTHWEST GRADIENT WILL PERSIST IN THIS AREA INTO THE WEEKEND.

.SHORT TERM FORECAST...RAIN IN SOUTHWEST ALASKA WILL PERSIST
OVERNIGHT IN THE SOUTHWEST FLOW AND UNSTABLE AIR. THE UPPER LEVEL
WAVE MOVING TOWARD COOK INLET SHOULD ALSO BRING RAIN TO
KODIAK...KENAI PENINSULA...ANCHORAGE...AND THE MAT-SU VALLEY.

.LONG TERM FORECAST...THE BIGGEST WEATHER MAKER WILL BE THE LOW
MOVING INTO THE GULF THIS WEEKEND. GALES WILL BE IN THE OFFSHORE AREA
WITH THIS LOW AND IT MAY BRING GOOD AMOUNTS OF RAINFALL ALONG THE
GULF COAST. THE RAIN WILL BE HEAVIER THE FURTHER EAST ONE GOES AND
AREAS ALONG THE EASTERN KENAI PENINSULA MAY MISS MUCH OF THE RAIN
DEEPENING HOW FAR EAST THIS LOW GOES.
A LOW EAST OF THE KAMCHATKA PENINSULA FRIDAY AFTERNOON WILL MOVE INTO
THE WESTERN BERING SEA SATURDAY. THIS LOW WILL NOT LAST LONG AS IT
WILL GET ABSORBED BY A STRONG LOW THAT WILL MOVE INTO THE SOUTHWEST
BERING SEA SUNDAY. THIS SYSTEM WILL MOVE ACROSS THE ALEUTIAN ISLANDS
AND BERING SEA EARLY NEXT WEEK AND BEARS WATCHING AS THE FORECAST
CENTRAL PRESSURE IS UNDER 960 MB ON THE GFS MODEL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

SEP 07