Gale Warning 661, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM ADT WED SEP 13 2006

.DISCUSSION...
ANALYSIS...
THE UPPER LEVEL TROUGH ANCHORED OVER THE THE SIBERIAN ARCTIC EXTENDS
SOUTH TO THE KAMCHATKA PENINSULA. AN UPPER LEVEL LOW IS SOUTH OF THE
ALASKA PENINSULA WHILE A RIDGE OF HIGH PRESSURE CONTINUES TO HOLD
OVER THE MAINLAND FROM THE GULF OF ALASKA.

SHORT TERM FORECAST...
THE MAIN ISSUE TODAY IS THE CONTINUED INCONSISTENCY OF THE MODEL
OUTPUT BEGINNING LATE FRI NIGHT. THERE REMAINS A HIGH LEVEL OF
UNCERTAINTY ABOUT THE POSITIONING AND STRENGTH OF THE STORM NOW
APPROACHING THE ALASKA PENINSULA FROM THE NORTH PACIFIC. WE EXPECT
THE APPROACHING UPPER LEVEL TROUGH AND FROM THE WESTERN BERING SEA TO
MOVE OVER THE EASTERN BERING SEA FRI MORNING AS THE SUPPORTING UPPER
LEVEL LOW TO THE NORTH PACIFIC STORM MERGES INTO THIS TROUGH. THE
ISSUE IS THE NEWEST MODEL SOLUTION IS CLOSING THIS LOW ALOFT AND AS A
RESULT THIS HOLDS THE SURFACE SYSTEM MUCH FURTHER SOUTH THAN
PREVIOUSLY FORECASTED AND MORE IN AGREEMENT WITH THE NAM. THE
BLOCKING RIDGE OF HIGH PRESSURE FROM THE GULF OVER THE MAINLAND
SHOULD HOLD BACK THE EASTWARD ADVANCEMENT OF THIS STORM. THIS SHOULD
ALSO RESULT IN A NORTHERLY STORM TRACK AND MOST LIKELY RESULT IN THE
LOW MOVING FURTHER NORTH INTO THE EASTERN BERING SEA AS FORECASTED BY
THE PREVIOUS MODEL RUNS. THE MAIN CHANGES TO THE FORECAST PACKAGE FOR
THIS AFTERNOON WILL REVOLVE AROUND TRENDING THE NEW FORECASTS TO THE
NEW MODEL OUTPUT. WE ARE RELUCTANT TO SELL OUT ON THE NEW OUTPUT DUE
TO THE INCONSISTENCY IN THE MODEL RUNS.

THE TIGHTENING GRADIENT OVER THE SOUTH CENTRAL REGION IS EXPECTED TO
PRODUCE A TYPICAL TURNAGAIN ARM WIND ALONG WITH THE STRONG CROSS
BARRIER FLOW AND RESULTANT DOWN SLOPE DRY CONDITIONS ACROSS THE KENAI
MOUNTAINS. . WE DO NOT SEE A GOOD INDICATION OF A RAPIDLY BUILDING
RIDGE OF HIGH PRESSURE ALONG THE GULF COAST REGION AND THEREFORE WILL
LEAVE THE FORECASTED WIND FOR SOUTHEAST PRINCE WILLIAM SOUND AS IS.
WE WILL CONTINUE TO HOLD THE RAIN OUT OF THE SOUTH CENTRAL REGION AND

THE EASTERN PRINCE WILLIAM SOUND AND COPPER RIVER BASIN ZONES THROUGH
FRI. THE TROPICALLY CONNECTED SOUTHERLY FLOW ASSOCIATED WITH THE
NORTH PACIFIC LOW WILL STEER MOISTURE INTO KODIAK AND THE WEST SIDE
COOK INLET TO THE WEST SIDE OF THE SUSITNA VALLEY ESPECIALLY ALONG
THE UPSLOPE REGIONS OF THE ALASKA RANGE.

LONGER TERM FORECAST...
THE MODELS CONTINUE TO BE INCONSISTENT RUN TO RUN IN THE LONGER TERM.
AS SUCH WE WILL MAINTAIN THE CURRENT FORECAST WITH VERY MINOR
TRENDING TOWARD THE NEW SOLUTION UNTIL THE MODELS BECOME MORE STABLE
AND CONSISTENT FROM RUN TO RUN. THE LAST COUPLE FO RUNS ARE SETTLING
ON A LOW SOUTHWEST OF THE GULF OF ALASKA ALONG WITH A STORM CENTERED
SOUTH OF ADAK AND WEAK HIGH PRESSURE EXTENDING FROM CANADA INTO THE
NORTHERN INTERIOR.

HYDROLOGY...
THE FLOOD ADVISORY FOR THE NELCHINA RIVER HAS BEEN CANCELED SINCE
WATER LEVELS HAVE CRESTED BELOW FLOW STAGE AND THE GLACIER DAM LAKE
THAT RELEASED CAUSING THE HIGH WATER IS NOW EMPTY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 130 132 150 155 160 165 170 350.
FIRE WEATHER...DONE.

SAM SEP 06