Small Craft Advisory 671, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT WED AUG 26 2009

.ANALYSIS AND UPPER LEVELS...
ALOFT...A SOMEWHAT COMPLICATED PATTERN IS IN PLACE ACROSS ALASKA THIS
AFTERNOON. A VERTICALLY STACKED CLOSED LOW IS IN THE CENTRAL
BERING...WITH ANOTHER CLOSED LOW SOUTH OF THE GULF OF AK. SHORTWAVE
RIDGING IS OVER SOUTHWEST AK...WITH A DEFORMATION ZONE OVER
SOUTHCENTRAL. A NARROW AND WEAKENING TROUGH AXIS IS ALSO OVER
SOUTHCENTRAL AK THIS AFTERNOON. RIDGING IS BEGINNING TO BUILD OVER
THE WESTERN BERING AND ALEUTIANS.

AT THE SURFACE...A BROAD LOW COMPLEX IS SOUTH OF THE GULF OF AK. THE
MOST PRONOUNCED LOW IS CURRENTLY SOUTH OF 50TH PARALLEL. MOISTURE
ASSOCIATED WITH THIS COMPLEX IS KEEPING RAIN AND SHOWERS ACROSS
COASTAL PORTIONS OF SOUTHCENTRAL. THE REMNANTS OF TYPHOON VAMCO ARE
NORTH OF THE CENTRAL ALEUTIANS...BRINGING STRONG WIND AND HEAVY RAIN
TO THE BERING SEA AND ALEUTIANS. FAIR WEATHER EXISTS BETWEEN THESE
TWO SYSTEMS WITH WEAKENING HIGH PRESSURE OVER SOUTHWEST AK.

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD AGREEMENT THROUGH THE START OF THE WEEKEND. THE
GENERAL PATTERN INVOLVES A LARGE LOW COMPLEX OVER THE NORTH
PACIFIC...WITH THE EMBEDDED LOW CURRENTLY SOUTH OF 50N MOVING
NORTHWESTWARD TO THE SOUTHERN TIP OF KODIAK ISLAND BY FRIDAY. THE
REMNANTS OF TYPHOON VAMCO WILL CROSS THE CENTRAL ALEUTIANS THURSDAY
AND BE ABSORBED INTO THE LOW COMPLEX ON FRIDAY. ELSEWHERE...HIGH
PRESSURE WILL BUILD OVER THE WESTERN ALEUTIANS THROUGH THE END OF THE
WEEK. THE GFS WAS USED TO CONSTRUCT THE AFTERNOON FORECAST PACKAGE.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
ACTIVE WEATHER WILL CONTINUE THROUGH THE END OF THE WEEK ACROSS
SOUTHCENTRAL AS THE LOW COMPLEX AFFECTS THE AREA. THE AFOREMENTIONED
DEFORMATION ZONE AND WEAKENING TROUGH OVER THE AREA WILL CONTINUE TO
RESULT IN LIGHT RAIN AND SHOWERS TAPERING OFF THROUGH TONIGHT. GOOD
ONSHORE FLOW AND A SURFACE LOW MOVING NORTHWESTWARD INTO THE GULF
WILL BRING UNSETTLED WEATHER AGAIN TOMORROW AND FRIDAY. PRIMARY
CONCERNS REVOLVE AROUND POTENTIALLY HEAVY RAIN ALONG EASTERN KENAI
PENINSULA AND PRINCE WILLIAM SOUND...AS WELL AS A STRENGTHENING
BARRIER JET ALONG THE COAST. WINDS UP TO STORM FORCE ARE
EXPECTED...WITH WIDESPREAD GALES ALONG COASTAL WATERS.

.SOUTHWEST...
CONDITIONS WILL REMAIN QUIET ACROSS MOST OF SOUTHWEST THROUGH THE END
OF THE WEEK AS THE MAJOR WEATHER FEATURES REMAIN TO THE SOUTH.
MOISTURE WILL GENERALLY BE ON THE INCREASE THOUGH...WITH SHOWERS
POSSIBLE ALONG AREAS OF ENHANCED TERRAIN. THE AKPEN WILL SEE RAIN AND
SHOWERS FROM FORMER TYPHOON VAMCO AS IT MOVES INTO THE NORTH
PACIFIC...AS WELL AS FROM THE LOW MOVING TO NEAR KODIAK ISLAND ON
FRIDAY.

.BERING SEA AND ALEUTIANS...
STRONG WIND AND WIDESPREAD RAIN ASSOCIATED WITH FORMER TYPHOON VAMCO
WILL IMPACT THE EASTERN HALF OF THE ALEUTIANS AND PRIBILOFS TONIGHT
THROUGH THURSDAY AS THE LOW MOVES INTO THE NORTH PACIFIC. HIGH
PRESSURE BUILDING AS THE SYSTEM DEPARTS WILL LEAVE QUIET WEATHER FOR
THE END OF THE WEEK...EXCEPT FOR THE CHARACTERISTIC LOW CLOUDS AND
PATCHY FOG.

.LONG TERM FORECAST...
THE UPCOMING WEEKEND WILL BE CHARACTERIZED BY THE LOW COMPLEX IN THE
GULF AND HIGH PRESSURE OVER THE ALEUTIANS. THIS WILL KEEP SHOWERS AND
RAIN ACROSS SOUTHCENTRAL AK. BY THE START OF NEXT WEEK A MORE ACTIVE
PATTERN LOOKS TO SET UP ACROSS THE BERING SEA AND ALEUTIANS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WATCH 141
         HIGH WIND WARNING 187
MARINE...STORM 120 130 132 172
         GALE 138 140 155 165 170 171 175
FIRE WEATHER...NONE

NRH AUG 09