Storm Warning 159, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1230 PM AKDT MON OCT 4 2010

.ANALYSIS AND UPPER LEVELS...A HIGH AMPLITUDE TROUGH IS CENTERED
OVER THE EASTERN BERING SEA AND WESTERN ALASKA. AT THE HEART OF
THE TROUGH IS A CLOSED UPPER LOW WHICH IS DROPPING SOUTHWARD ACROSS
THE EASTERN BERING TOWARD THE EASTERN ALEUTIANS AND SOUTHERN ALASKA
PENINSULA. SAINT GEORGE ISLAND OBSERVED SOME ENHANCED WINDS AS THIS
LOW PASSED JUST TO THE EAST THIS MORNING. THE 12Z SOUNDING FROM
SAINT PAUL ALSO INDICATES AN UNSTABLE WELL MIXED ATMOSPHERE.
THEREFORE...WOULD EXPECT THESE LOCALLY STRONGER GUSTS TO CONTINUE
BOTH IN THE VICINITY OF THIS UPPER CENTER AS WELL AS NEAR NEAR
SHOWERS. ON THESE EAST SIDE OF THE TROUGH EMBEDDED SHORT-WAVES ARE
TRACKING NORTHWARD FROM THE GULF OF ALASKA AND ACROSS THE MAINLAND.
MOST OF THE SHOWERS WITH THESE SHORT-WAVES ARE HANGING UP ALONG THE
COAST. ANY SHOWERS WHICH DO SURVIVE THE JOURNEY INLAND ARE CONFINED
PRIMARILY TO ALONG THE MOUNTAINS. THE NEXT MAJOR STORM (CURRENTLY
NEAR 48N 158W) IS RAPIDLY TRACKING TOWARD THE GULF OF ALASKA THANKS
TO A 150+ KT JET.

.MODEL DISCUSSION...THERE ARE MINOR DIFFERENCES IN THE TRACK AND
SPEED OF SYSTEM HEADED TO THE GULF...BUT MODEL SOLUTIONS ARE GROUPED
IN THE SAME VICINITY AND THERE IS GOOD RUN-TO RUN CONSISTENCY. WILL
CONTINUE TO FINE TUNE FORECASTS AS WE GET CLOSER TO THE EVENT.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...WINDS ACROSS THE GULF WATERS WILL RAPIDLY
INCREASE TONIGHT INTO TUESDAY MORNING AS A 970S LOW MOVES INTO
THE CENTRAL GULF. UNLIKE THE PAST COUPLE STORMS THIS ONE WILL
STALL OVER THE NORTHERN GULF AS THE JET MOVES OFF TO THE EAST.
ALSO...STRONG OFFSHORE FLOW WILL MAINTAIN DRY LOW LEVELS AND LIMIT
THE AMOUNT OF PRECIP REACHING THE GROUND.  EXPECT NEARLY ALL THE
PRECIP TO FALL IN THE PRINCE WILLIAM SOUND REGION. EVEN THERE
RAINFALL AMOUNTS WILL GENERALLY BE LIGHT DUE TO THE OFFSHORE FLOW.
ANYTHING THAT DOES MAKE IT ACROSS THE COASTAL RANGE WILL BE BRIEF
AND VERY LIGHT. THE REMNANTS OF THE UPPER LOW CURRENTLY OVER THE
EASTERN BERING WILL MOVE THROUGH THE TROUGH AND BEGIN TO TRACK
NORTHWARD ACROSS THE WESTERN GULF TUESDAY NIGHT. THIS WILL AID IN
FORMATION OF A SECODNARY LOW NEAR THE SOUTHERN KENAI PENINSULA.
THIS WILL BRING A CHANCE OF RAIN TO WESTERN PORTIONS OF SOUTHCENTRAL
LATE WEDNESDAY THROUGH THURSDAY.

SOUTHWEST ALASKA...AS THE UPPER LOW OVER THE EASTERN BERING DROPS
SOUTHWARD AND MAJOR SYSTEM MOVES INTO THE GULF OF ALASKA TONIGHT
FLOW WILL BECOME OFFSHORE OVER SOUTHWEST ALASKA AND CONDITIONS WILL
DRY OUT. MARGINALLY COOLER AIR WILL DROP DOWN FROM THE NORTH THE
NEXT COUPLE DAYS RESULTING IN SEASONABLE TEMPERATURES. BENIGN
WEATHER WILL PERSIST FOR THROUGH THE REMAINDER OF THE WEEK.

BERING SEA/ALEUTIANS...THE REGION WILL REMAIN IN THE BACK SIDE OF
THE LONG-WAVE TROUGH THROUGH THE WEEK. WEAK FEATURES EMBEDDED IN
THE NORTHWEST FLOW WILL FOCUS AREAS OF SHOWERS. WEAK COLD ADVECTION
ACROSS THE RELATIVELY WARM WATERS OF THE BERING SEA WILL ALSO AID
IN FORMATION OF SHOWERS.

.LONG TERM FORECAST...MEAN TROUGH POSITION WILL SHIFT EASTWARD AS
WE HEAD THROUGH THE WEEK. THEREFORE...TRACK OF NEXT MAJOR STORM
WILL BE TOWARD SOUTHEAST ALASKA LATE IN THE WEEK. GFS/ECMWF ARE
IN AGREEMENT ON BRINGING A LARGE UPPER LOW OUT OF RUSSIA AND INTO
THE BERING SEA LATE THIS WEEK...WHICH WON'T BE MUCH OF A STORM BY
BERING SEA STANDARDS...BUT AS THIS WILL LIKELY LEAD TO RECENTERING
THE TROUGH BACK WESTWARD WITH POTENTIAL FOR ANOTHER MAJOR GULF
STORM EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...120 130.
         GALE WARNING...132 138 140 172.
FIRE WEATHER...NONE.

SEB OCT 10