Small Craft Advisory 700, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
115 PM AKDT THU SEP 3 2009

.ANALYSIS AND UPPER LEVELS...TWO CUT-OFF LOWS DOMINATE THE FORECAST
AREA THIS MORNING. THE MORE SIGNIFICANT OF THE TWO IS POSITIONED
JUST SOUTH OF THE GULF TRACKING EASTWARD. ITS CYCLONIC CIRCULATION
EXTENDS OVER THE SOUTHERN MAINLAND AND EASTERN BERING...WITH WEAK
EMBEDDED SHORT-WAVES PRODUCING A FEW SHOWERS FROM THE GULF TO
BRISTOL BAY AND THE ALASKA PENINSULA. SKIES ARE CLEARING OVER
SOUTHCENTRAL AS THE SHOWERS ROTATE SOUTHWESTWARD.

THE SECOND CUT-OFF IS A MUCH SMALLER VERTICALLY STACKED LOW JUST
SOUTHWEST OF THE WESTERN ALEUTIANS. A GALE FORCE FRONT IS WOUND
FAIRLY TIGHT NEAR THE LOW CENTER. A RIDGE OF HIGH PRESSURE NOSES
UP BETWEEN THE TWO UPPER LOWS ACROSS THE CENTRAL AND NORTHERN
BERING.

.MODEL DISCUSSION...MODELS ARE VERIFYING WELL AND SOLUTIONS ARE
IN GOOD AGREEMENT THROUGH THE WEEKEND. THERE ARE SMALL DIFFERENCES
IN THE DETAILS OF SHORT-WAVES ROTATING ACROSS SOUTHCENTRAL SATURDAY
AND SUNDAY...BUT NONE OF THESE FEATURES SEEMS REALLY STRONG AND
DONT EXPECT ANY WELL ORGANIZED AREAS OF RAIN. INSTEAD...THESE
SHOULD PRODUCE MAINLY ISOLATED TO SCATTERED SHOWERS AND SO THAT
EXACT PLACEMENT OF THESE FEATURES WILL NOT GREATLY IMPACT THE
FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL...THE CLEARING OCCURRING ACROSS SOUTHCENTRAL TODAY
WILL NOT LAST VERY LONG. AN EASTERLY WAVE CURRENTLY OVER THE YUKON
WILL ROTATE WESTWARD INTO THE EASTERN COPPER BASIN TONIGHT AND THEN
SOUTHWESTWARD TOWARD PRINCE WILLIAM SOUND. THIS WILL KEEP AREAS
FARTHER WEST UNDER MOSTLY SUNNY SKIES ON FRIDAY. WITH OFFSHORE FLOW
TEMPERATURES WILL WARM UP INTO THE 60S TO 70S. OTHER WEAK WAVES
EMBEDDED WITHIN THE CYCLONIC ROTATION AROUND THE PERIPHERY OF THE
LOW SOUTH OF THE GULF WILL CONTINUE TO MOVE ACROSS SOUTHCENTRAL
THROUGH THE WEEKEND. MOST OF THESE LOOK TO BE WEAK AND THERE ARE
BREAKS IN BETWEEN THEM. THEREFORE...EXPECT VARIABLE CLOUDS WITH
ISOLATED TO SCATTERED SHOWERS ACROSS THE REGION. ALL OF THIS WILL
BE PUSHED OFF TO THE EAST SUNDAY NIGHT AND MONDAY AS THE WESTERLIES
RETURN.

SOUTHWEST...CLOUDS AND SHOWERS WILL DECREASE THIS AFTERNOON AND
EVENING AS THE UPPER LOW MOVES FARTHER AWAY AND RIDGE OVER THE
BERING BUILDS JUST TO THE NORTH OVER INTERIOR ALASKA. SOUTHWEST
ALASKA WILL REMAIN UNDER THE INFLUENCE OF THIS RIDGE THROUGH THE
WEEKEND RESULTING IN SUNNY AND WARM WEATHER.

BERING SEA/ALEUTIANS...THE LOW OUT NEAR THE WESTERN ALEUTIANS HAS
LITTLE IN THE WAY OF STEERING WINDS SO WILL BE SLOW TO MOVE. IT
WILL REMAIN NEARLY STATIONARY THROUGH FRIDAY AND THEN TRACK SLOWLY
EASTWARD OVER THE WEEKEND.

.LONG TERM FORECAST...ECMWF AND GFS ARE CONVERGING ON A SOLUTION
WHICH TRACKS THE ALEUTIAN LOW TO A POSITION SOUTH OF THE ALASKA
PENINSULA AND KODIAK ISLAND EARLY NEXT WEEK...BRINGING RAIN TO
MOST OF THE SOUTHERN MAINLAND. A LARGE SPREAD REMAINS IN THE
ENSEMBLES FOR MID TO LATE WEEK...ALTHOUGH ENSEMBLE MEANS DO
INDICATE HIGH AMPLITUDE TROUGH REMAINING CENTERED NEAR 160W.
ALSO...MOST OF THE ENSEMBLE MEMBERS BRING A DEEP LOW FROM THE
PACIFIC NORTHWARD INTO THE GULF MID TO LATE WEEK. BOTTOM LINE...IT
LOOKS TO REMAIN ACTIVE FROM THE EASTERN BERING ACROSS THE SOUTHERN
MAINLAND AND GULF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...172 175 176.
FIRE WEATHER...NONE.

SEB SEP 09