Small Craft Advisory 674, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTED
SOUTHCENTRAL AND SOUTHWEST ALASKA
145 PM AKDT THU AUG 27 2009

.ANALYSIS AND UPPER LEVELS...STRONG RIDGES ARE POSITIONED OVER
THE NORTHWEST PACIFIC/WESTERN BERING AND OVER THE WESTERN U.S.
TWO SIGNIFICANT LOWS ARE EMBEDDED WITH IN THE HIGH AMPLITUDE
TROUGH IN BETWEEN...THE FORMER TYPHOON (WHICH IS STILL A STORM
FORCE LOW) IS DROPPING SOUTH OF THE EASTERN ALEUTIANS AND A
SLIGHTLY WEAKER LOW IS TRACKING NORTHWARD INTO THE SOUTHERN
GULF OF ALASKA WITH A STRONG FRONTAL SYSTEM SPREADING OUTWARD
ACROSS THE GULF AND TOWARD SOUTHCENTRAL.

THE LATEST QUIKSCAT IMAGE (AROUND 1720 UTC) SHOWS MAX GALES TO
MIN STORMS OVER THE EASTERN ALEUTIANS...BUT THESE WINDS ARE VERY
SLOWLY DIMINISHING AS THE STORM TRACKS SOUTHEASTWARD. A SURFACE
TROUGH EXTENDING FROM THIS LOW IS TRACKING WESTWARD ACROSS
WESTERN ALASKA PRODUCING A SOLID LINE OF SHOWERS. SOUTHCENTRAL
ALASKA IS CURRENTLY IN A BREAK BETWEEN THIS TROUGH WHICH MOVED
THROUGH OVERNIGHT AND THE APPROACHING SYSTEM...ALTHOUGH CLOUDS
AND RAIN ARE RAPIDLY APPROACHING FROM THE GULF AND CONDITIONS
WILL HEAD DOWNHILL THIS AFTERNOON OVER THE EASTERN COPPER BASIN
AND PRINCE WILLIAM SOUND.

.MODEL DISCUSSION...MODELS ARE IN VERY GOOD AGREEMENT IN THE
SHORT-TERM WITH ONLY MINOR DIFFERENCES IN POSITIONS/STRENGTH
OF LOWS AND FRONTS. THEREFORE...AFTERNOON PACKAGE WILL
REFLECT FINE-TUNING OF FORECAST WITH NO MAJOR CHANGES.

.SHORT TERM FORECAST...

.SOUTHCENTRAL ALASKA...THE OCCLUDED FRONT WILL QUICKLY MOVE WESTWARD
ACROSS COASTAL SOUTHCENTRAL TONIGHT AND THEN DISSIPATE OVER THE
WESTERN GULF FRIDAY. THIS SHOULD BRING SOME RAIN TO MOST
LOCATIONS TONIGHT...WITH THE MOST SIGNIFICANT RAIN ACROSS PRINCE
WILLIAM SOUND. ANOTHER ROUND OF RAIN WILL QUICKLY FOLLOW LATE
THURSDAY NIGHT AND FRIDAY AS THE UPPER CLOSED LOW OPENS INTO A TROUGH
AND ROTATES ACROSS SOUTHCENTRAL. THE GULF LOW WILL MERGE WITH THE
FORMER TYPHOON AND THEN MOVE BACK INTO THE GULF AS A LARGE VERTICALLY
STACKED LOW ON SATURDAY. EASTERLY WAVES EMBEDDED WITHIN THE UPPER
FLOW WILL CONTINUE TO MOVE ACROSS SOUTHCENTRAL THROUGH SATURDAY. ON
SUNDAY...MODELS INDICATE A TROUGH/FRONT DROPPING DOWN THROUGH
INTERIOR ALASKA...BUT THERE IS A LOT OF UNCERTAINTY AS TO HOW FAR
SOUTH IT WILL ACTUALLY DROP...SO FOR NOW WILL INCLUDE JUST A CHANCE
OF PRECIPITATION ALONG THE NORTHERN TIER OF SOUTHCENTRAL.

.SOUTHWEST ALASKA...THE SURFACE TROUGH MOVING WESTWARD ACROSS
SOUTHWEST ALASKA WILL DISSIPATE THIS EVENING AS IT RUNS INTO
THE BERING RIDGE. DRY NORTHERLY FLOW WILL THEN DOMINATE THROUGH
FRIDAY ON THE BACK SIDE OF THE GULF LOW AND THE DEPARTING ALEUTIAN
LOW. THE BERING RIDGE WILL BUILD TOWARD SOUTHWEST ALASKA OVER THE
WEEKEND. HOWEVER...NORTHERN PORTIONS OF SOUTHWEST MAY BE CLIPPED
BY ENERGY MOVING OVER TOP OF THE RIDGE ON SUNDAY. FOR NOW WILL
JUST INCLUDE A CHANCE OF PRECIPITATION FOR THIS AREA.

.BERING SEA/ALEUTIANS...STRONG WINDS WILL PERSIST OVER THE EASTERN
ALEUTIANS AND SOUTHERN ALASKA PENINSULA ON THE BACK SIDE OF THE
DEPARTING STORM THROUGH FRIDAY...ALTHOUGH WITH A STEADY BUT GRADUAL
WEAKENING TREND. ELSEWHERE ACROSS THE BERING REGION THE LARGE RIDGE
OF HIGH PRESSURE WILL DOMINATE THE WEATHER THROUGH SATURDAY. A TROUGH
WILL SWING OUT OF RUSSIA SATURDAY AND START TO PUSH THE RIDGE SOUTH
AND EASTWARD ALLOWING UNSETTLED WEATHER TO MOVE INTO THE WESTERN
BERING AND ALEUTIANS.

.LONG TERM FORECAST...MEDIUM RANGE MODELS INDICATE A PROGRESSIVE
PATTERN THROUGH NEXT WEEK WITH TROUGH OVER THE WESTERN BERING
SUNDAY MOVING TO MAINLAND ALASKA BY THE END OF THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WATCH ZONE 141.
MARINE...GALE WARNING 120 130 132 155 165 170 171 172.
FIRE WEATHER...NONE.

SEB AUG 09