High Wind in Alaska, September 2 to 3, 2012

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
110 PM AKDT SUN SEP 2 2012

.ANALYSIS AND UPPER LEVELS...LONG-WAVE TROUGH IS CENTERED OVER
THE BERING SEA WITH A STRONG UPPER JET ROUNDING THE BOTTOM OF
THE TROUGH FROM THE SEA OF OKHOTSK TO THE ALEUTIANS AND ACROSS
THE GULF TO SOUTHEAST ALASKA. A STRONG SHORT-WAVE TROUGH ACROSS
THE EASTERN BERING SEA AND ALASKA PENINSULA IS SWINGING
NORTHEASTWARD TOWARD MAINLAND ALASKA ALONG WITH A MATURE LOW
AND OCCLUDING FRONTAL SYSTEM. THE DEPTH OF THE SURFACE LOW (AROUND
982 MB) AND STRENGTH OF UPPER LEVEL FORCING IS PRODUCING WIDESPREAD
STRONG WINDS AND LOCALIZED HEAVY RAIN ACROSS SOUTHWEST ALASKA...
WITH DETERIORATING CONDITIONS OVER THE GULF AND SOUTHCENTRAL ALASKA.

MEANWHILE...ANOTHER SHORT-WAVE MOVING OUT OF ASIA IS BEGINNING TO
DEVELOP ANOTHER SURFACE LOW NEAR THE KAMCHATKA PENINSULA. UPPER
LEVEL JET WITH THIS IS QUITE IMPRESSIVE FOR THIS TIME OF YEAR...AT
160 KT PLUS. EXPECT THIS TO RAPIDLY DEVELOP INTO AN EVEN STRONGER
SYSTEM THAN THE CURRENT ONE AND PRODUCE WIDESPREAD IMPACTS ACROSS
THE ALASKA REGION OVER THE NEXT FEW DAYS.

.MODEL DISCUSSION...MODELS ARE IN EXCELLENT AGREEMENT AND FORECAST
CONFIDENCE IS ABOVE AVERAGE.

.SHORT TERM FORECAST...BACK TO BACK POWERFUL SYSTEMS WILL IMPACT
THE REGION OVER THE NEXT FEW DAYS. THE GREATEST IMPACT OF THESE
SYSTEMS WILL BE WIDESPREAD STRONG WINDS. ALTHOUGH STORMS LIKE THIS
ARE VERY COMMON DURING THE WINTER MONTHS IT IS RARER TO SEE THEM
THIS EARLY IN THE SEASON. THE BIG DIFFERENCE IS THE GROUND IS NOT
FROZEN AND ALL THE LEAVES ARE STILL ON THE TREES. THIS INCREASES
THE LIKELIHOOD OF OF FALLING TREES AND BRANCHES AS WELL AS POWER
OUTAGES. THE STRONGEST WINDS WITH THE FIRST STORM ARE EXPECTED
ALONG TURNAGAIN ARM AND HIGHER ELEVATIONS. WINDS LOOK LIKE THEY
WILL PEAK SOMEWHERE NEAR THE WARNING THRESHOLD. BECAUSE THIS IS
AN UNUSUALLY STRONG EARLY SEASON STORM AND BECAUSE OF THE HIGHER
THREAT TO FALLING TREES DECIDED TO ISSUE A HIGH WIND WARNING FOR
THIS BORDERLINE SITUATION. WITH STRONG SOUTHERLY FLOW ALOFT THE
FRONTAL SYSTEM WILL PUSH INLAND...PRODUCING FAIRLY WIDESPREAD
STRONG AND GUSTY WINDS. MODERATE TO HEAVY RAINFALL CAN BE EXPECTED
RIGHT OUT AHEAD OF THE UPPER SHORT-WAVE. HOWEVER...EVERYTHING WILL
MOVE THROUGH QUICKLY SO HEAVY RAIN SHOULD NOT LAST VERY LONG IN
ANY ONE LOCATION.

THE FIRST STORM SYSTEM WILL EXIT TO THE NORTH MONDAY AFTERNOON
AND MONDAY NIGHT WHILE THE SECOND IS BOMBING OUT OVER THE WESTERN
ALEUTIANS. THIS STORM WILL ULTIMATELY TAKE A NEARLY IDENTICAL
TRACK TO THE FIRST STORM PRODUCING A LOT OF THE SAME TYPES OF
WEATHER. THE DIFFERENCE IS EVERYTHING WILL BE STRONGER...WITH THE
CENTRAL PRESSURE EXPECTED TO BOTTOM OUT NEAR 970 MB (ABOUT 10 MB
DEEPER THAN THIS FIRST STORM). ASSUMING THIS FORECAST REMAINS ON
TRACK IT LOOKS LIKE A NO DOUBTER HIGH WIND WARNING FOR TURNAGAIN
ARM AND HIGHER ELEVATIONS OF ANCHORAGE. THIS RAISES EVEN MORE
CONCERN FOR DOWNED TREES AND POWER LINES THAN THE FIRST STORM.
A SPECIAL WEATHER STATEMENT HAS BEEN ISSUES TO HIGHLIGHT THESE
CONCERNS.

.LONG TERM FORECAST...THINGS WILL WIND DOWN WEDNESDAY AND THURSDAY
AS THE SECOND STORM EXITS TO THE NORTH. THE LONG-WAVE TROUGH WILL
SHIFT EASTWARD A BIT AS A RIDGE MOVES INTO THE NORTHWEST PACIFIC
AND FAR WESTERN BERING SEA. THIS WILL ALLOW A TROUGH TO DROP DOWN
OUT OF THE RUSSIAN ARCTIC THURSDAY AND FRIDAY...DIGGING SOUTHEASTWARD
INTO THE GULF BY THE WEEKEND AND LIKELY RESULTING IN ANOTHER ROUND
OF RAIN FOR THE SOUTHERN MAINLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101.
MARINE...STORM WARNING...160 165 170 172 175 176.
         GALE WARNING...120 125 129 130 132 138 140 150 155
                        171 179 180 185.
FIRE WEATHER...NONE.

SEB SEP 12