Gale Warning 416, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
230 PM AKDT SUN APR 19 2009

.MODEL DISCUSSION...MODEL INITIALIZATIONS WERE GOOD AND FORECAST OF
SYNOPTIC FEATURES ARE REASSONABLE AND IN EXCELLENT AGREEMENT THROUGH
WED. THE TREND HAS BEEN TO SLOW DOWN THE ONSET OF SW FLOW AND
MOISTURE ADVECTION INTO SOUTHCENTRAL. AFTERNOON PACKAGES WILL BE
BASED ON A BLEND THE THE NAM AND GFS IN THE EAST AND SOME SLIGHT
ADJUSTMENT WITH THE GFS IN THE WEST.

.UPPER LEVELS...
500 MB...THE OMEGA BLOCKING PATTERN SHIFTS EAST THROUGH THIS WEEK.
THE CUT-OFF LOW OVER THE GULF MOVES EAST INTO CANADA AS A HIGH
AMPLITUDE RIDGE BUILDS OVER THE WESTERN GULF AND THE MAINLAND TUE
NIGHT. THE RIDGE AXIS MOVES EAST TO OVER THE WEST/CENTRAL GULF AND
WESTERN CANADA THU AFTERNOON AND SETS UP SOUTHWESTERLY FLOW OVER THE
MAINLAND. FURTHER WEST...THE LOW NEAR KAMCHATKA MOVES INTO THE NORTH
CENTRAL BERING SEA THU AND INTENSIFIES.

.SHORT TERM FORECAST...

.EAST...SHORT WAVE OVER THE WESTERN GULF/SOUTHCENTRAL ALASKA WILL
WEAKEN AS IT SHIFTS WEST TONIGHT. THE GENERAL LOW COMPLEX OVER THE
GULF OF ALASKA WILL MOVE EAST AS HIGH PRESSURE BUILDS OVER THE GULF
AND MAINLAND TUE.  A WEAK INVERTED TROUGH WILL LIKELY OVER ALONG THE
NORTHERN GULF THROUGH TUE...BUT SHOULD WEAKEN WED AS HIGH PRESSURE
TAKES HOLD. UNSTABLE CONDITIONS ARE LIKELY OVER THE EASTERN COPPER
RIVER BASIN MON AND TUE AS A WEAK THERMAL TROUGH SETS OVER THE AREA.
OTHERWISE...GENERALLY WARMER AND DRIER WEATHER IN STORE FOR MUCH OF
EASTERN ZONES THROUGH THE MIDDLE OF THIS WEEK. SHOULD SEE INCREASING
CLOUDS WITH A CHANCE OF PRECIPITATION INTO SOUTHCENTRAL ON THU AS
FRONTAL TROUGH APPROACHES.

.WEST...
SHORT WAVE MOVING THROUGH SW ALASKA THIS AFTERNOON IS SHOWING SIGNS
OF WEAKENING WITH WARMING CLOUD TOPS AND GREATLY REDUCED RADAR
RETURNS. SUBSIDENCE ON THE BACKSIDE OF TROUGH PRODUCED FOG OVER
EASTERN BRISTOL BAY THIS MORNING. ABUNDANT LOW LEVEL MOISTURE AND A
BUILDING RIDGE TONIGHT WILL LIKELY PRODUCE WIDESPREAD FLOW OVER
BRISTOL BAY TONIGHT...AS WILL AS PORTIONS OF THE DELTA. LOW CENTER
NEAR KAMCHATKA WILL SLOWLY WEAKEN AND SHIFT WEST. FRONTAL TROUGH OVER
THE WESTERN ALEUTIANS THIS MORNING WILL MOVE JUST EAST OF THE
DATELINE EARLY MON. A SECONDARY LOW DEVELOPS ALONG THE FRONT MON AND
INTENSIFIES AS IT MOVES TO THE NORTH CENTRAL BERING SEA TUE
AFTERNOON. THE ASSOCIATED FRONT WHICH SLOWS SOME MON WITH DEVELOPING
LOW...MOVES TO THE AK PEN AND AND DELTA/WESTERN BRISTOL BAY BY EARLY
WED MORNING. EXPECT SOUTHERLY GALES WITH AND IN ADVANCE OF FRONTAL
SYSTEM. THE AIR IN ADVANCE OF THE FRONTAL TROUGH WILL BE WARM ENOUGH
THAT PRECIPITATION WILL BE A MIX OR RAIN AND SNOW. FRONT WEAKENS AS
IT MOVES INLAND WED AND THU. BROAD SOUTHWESTERLY FLOW SETS UP OVER
MUCH OF THE BERING SEA AND SW ALASKA THU WITH CENTRAL NEUTRAL
TEMPERATURE ADVECTION.

.LONG TERM FORECAST...A PATTERN CHANGE IS UNDERWAY STARTING TODAY FOR
MAINLAND ALASKA AND THE BERING SEA. AS THE RIDGE MOVES EAST TO BE
CENTERED OVER MAINLAND ALASKA BY MIDWEEK IT WILL BE REPLACED BY MOIST
SOUTHERLY FLOW THAT WILL SPREAD ABUNDANT MOISTURE TO THE BERING AND
MOST OF MAINLAND ALASKA. IN GENERAL...AN UNSEASONABLY CLEAR AND WARM
START TO THE WEEK WILL DETERIORATE TO COOLER AND MUCH WETTER
CONDITIONS BY THE END OF THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...170 172 179
FIRE WEATHER...NONE.

RMC APR 09