Small Craft Advisory 543, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT SAT JUL 11 2009

.ANALYSIS AND UPPER LEVELS...
ALOFT...UPPER RIDGING CONTINUES OVER THE MAINLAND WITH UPPER LOWS
OVER THE KAMCHATKA PENINSULA AND SOUTH OF THE AKPEN. THIS PATTERN IS
EXPECTED TO REMAIN FAIRLY STEADY STATE THROUGH TUESDAY.

AT THE SURFACE...THE THERMAL TROUGH IS DRAPED ALONG THE ALASKA RANGE
WITH HIGH PRESSURE EXTENDING FROM THE GULF OF ALASKA INTO THE AKPEN.
A LOW SOUTHWEST OF SHEMYA IS EVIDENT ON SATELLITE IMAGERY...WITH AN
ASSOCIATED FRONT OVER THE CENTRAL BERING. THIS LOW WILL MOVE
NORTHWARD THROUGH TUESDAY...WITH THE FRONT MOVING ACROSS THE
ALEUTIANS AND INTO THE AKPEN THROUGH LATE MONDAY.

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD AGREEMENT THROUGH TUESDAY...KEEPING THE RIDGE
OVER THE MAINLAND WHILE A SERIES OF LOWS AFFECT THE BERING. AS
USUAL...DIFFERENCES ARISE WITH REGARDS TO PLACEMENT AND INTENSITY OF
INDIVIDUAL FEATURES. THE AFTERNOON PACKAGE WAS CONSTRUCTED USING THE
GFS SOLUTION THROUGH THE SHORT TERM WITH ONLY MINOR CHANGES MADE TO
THE EXISTING FORECAST.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
MAIN FORECAST PROBLEMS OVER THE NEXT SEVERAL DAYS WILL REVOLVE AROUND
INLAND PENETRATION OF THE MARINE LAYER...AFTERNOON CONVECTION...AND
REMNANT HAZE AND SMOKE. THE MARINE LAYER HAS BECOME ENTRENCHED ACROSS
MOST COASTAL PORTIONS OF SOUTHCENTRAL THIS MORNING. CURRENT THINKING
IS AFTERNOON HEATING WILL BE ABLE TO MIX COOLER AIR OUT FOR LOCATIONS
FURTHER INLAND...BUT AREAS ALONG THE IMMEDIATE COAST MAY NOT CLEAR
OUT COMPLETELY. EXPECT THE MARINE LAYER TO SURGE WELL INLAND AGAIN
TONIGHT. NEXT...THE THERMAL TROUGH REMAINS WELL ESTABLISHED ALONG THE
ALASKA RANGE...LEADING TO INITIATION OF AFTERNOON SHOWERS AND
ISOLATED THUNDERSTORMS THE NEXT SEVERAL DAYS. EXPECTING MAJORITY OF
CONVECTION OF OCCUR ALONG AREAS OF ENHANCED TERRAIN. LASTLY...HAZE
AND SMOKE CONTINUE TO BE SLOW TO CLEAR OUT OF SOUTHCENTRAL...WITH
GRADUALLY IMPROVING CONDITIONS THROUGH THE BEGINNING OF THE WEEK.

.SOUTHWEST...
FAIR CONDITIONS WILL PERSIST ACROSS SOUTHWEST TODAY AND TOMORROW AS
HIGH PRESSURE REMAINS IN CONTROL. ONE EXCEPTION WILL BE AFTERNOON
SHOWERS AND ISOLATED THUNDERSTORMS ALONG THE ALASKA RANGE IN RESPONSE
TO THE THERMAL TROUGH. MOISTURE AND PRECIPITATION WILL BE ON THE
INCREASE MONDAY AND TUESDAY AS A DECAYING FRONT MOVES INTO THE AREA.

.BERING SEA AND ALEUTIANS...
WIDESPREAD RAIN ACROSS THE ISLANDS TODAY AND TOMORROW AS THE
AFOREMENTIONED LOW AND ASSOCIATED FRONT IMPACT THE AREA. RAIN WILL
CONTINUE ACROSS THE PRIBILOFS AND EASTERN ISLANDS THROUGH MONDAY AS
THIS FRONT MOVES ACROSS THE EASTERN BERING. DRIER CONDITIONS WILL
PERSIST ACROSS THE WESTERN AND CENTRAL ISLANDS AS BULK OF MOISTURE
STAYS EAST.

.LONG TERM FORECAST...
MODELS CONTINUE TO TREND TOWARDS A PATTERN CHANGE BY THE SECOND HALF
OF THE WEEK...WITH THE RIDGE BREAKING DOWN OVER MAINLAND ALASKA.
UNSETTLED WEATHER CAN BE EXPECTED OVER THE BERING AND
ALEUTIANS...WITH A RETURN TO MORE SEASONABLE TEMPERATURES AND HIGHER
CHANCES OF PRECIPITATION OVER THE SOUTHERN MAINLAND AS WE HEAD INTO
THE WEEKEND.

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

NRH JUL 09