Gale Warning 662, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AKDT FRI SEP 17 2010

.MODEL DISCUSSION...
MODELS IN REASONABLY GOOD AGREEMENT. NAM PREFERRED IN THE SHORT TERM
FOR ITS HIGHER DETAIL. IN THE LONGER RUN...TRENDED INHERITED FORECAST
TOWARDS THE GFS.

.UPPER LEVELS...
BLOCKING UPPER LEVEL RIDGE HOLDS FIRMLY THROUGH THE WEEKEND...THEN
EDGES GRADUALLY EASTWARD ON MONDAY AND TUESDAY BEFORE BEING FORCED
INTO WESTERN CANADA BY THE END OF THE COMING WEEK. LONG WAVE TROUGH
ALOFT ACROSS BERING SEA AND EASTERN RUSSIA HOLD THROUGH THE WEEKEND
THEN SLOWLY PUSHES EASTWARD INTO WESTERN ALASKA AND THE GULF OF
ALASKA BY MIDWEEK.

.SURFACE ANALYSIS...
BROAD HIGH PRESSURE PERSISTS OVER THE GULF OF ALASKA AND MOST OF
MAINLAND ALASKA. AN EXTENSIVE AREA OF LOW CLOUDS AND FOG WAS
OBSERVABLE ON VISIBLE SATELLITE THURSDAY EVENING ACROSS THE EASTERN
BERING SEA...COASTAL SOUTHWEST ALASKA...COOK INLET...PRINCE WILLIAM
SOUND...AND MUCH OF THE GULF. SOME WEAK TROUGHING ALONG THE GULF
COAST TODAY SHOULD ENCOURAGE OFFSHORE FLOW AND HELP ANCHORAGE AND THE
KENAI PENINSULA CLEAR OUT TEMPORARILY TODAY. HOWEVER NO RELIEF
EXPECTED FOR KODIAK OR SOUTHERN PRINCE WILLIAM SOUND.
OUT WEST...A WELL STACKED 989 MB LOW JUST SOUTH OF ADAK SWINGS
NORTHEASTWARD TO NEAR DUTCH HARBOR BEFORE DISSIPATING BY LATE SAT
NIGHT. NEW LOW DEVELOPS JUST SOUTH OF THE KAMCHATKA PENINSULA THIS
MORNING AND MOVES TO THE WESTERN ALEUTIANS EARLY SUNDAY. PLENTY OF
BOTH RAIN ASSOCIATED WITH BOTH WESTERN LOWS. GALE FORCE WINDS WILL BE
LIMITED TO THE WESTERN ALEUTIANS WITH THE FIRST SYSTEM...BUT WILL BE
SPREAD ACROSS MOST OF THE BERING WITH THE SECOND.

.SHORT TERM FORECAST...
SUBSIDENCE INVERSION ALOFT GRIPPING MUCH OF SOUTHERN ALASKA AND THE
GULF LIKELY TO HOLD THROUGH SUNDAY. BUT SYSTEM APPROACHING FROM THE
WEST ON MONDAY SHOULD TRIGGER SUFFICIENT MIXING TO FINALLY BREAK THE
INVERSION.
FIRST BERING LOW LACKS THE STRENGTH TO BREAK DOWN THE BLOCKING HIGH
BUT SECOND LOW SHOULD BE ABLE TO SPREAD CLOUDS AND LIGHT RAIN INTO
SOUTHWEST ALASKA BEGINNING MONDAY.

.LONG TERM FORECAST...
MODELS ARE INDICATING POTENTIAL PATTERN SHIFT MIDDLE OF NEXT WEEK.
ONCE BLOCKING RIDGE BREAKS DOWN PATTERN SHOULD BECOME MUCH MORE
ACTIVE...WITH JET STREAM STEERING LOWS ACROSS THE ALEUTIANS AND
TOWARDS MAINLAND ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 176.
FIRE WEATHER...NONE.

ASB SEP 10