Gale Warning 572, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKDT TUE SEP 8 2009

.ANALYSIS AND UPPER LEVELS...
A LARGE UPPER LEVEL CLOSED LOW IS SITUATED SOUTH OF THE AKPEN REGION
WHILE ANOTHER LOW IS DROPPING OUT OF THE ARCTIC INTO THE BERING.  A
FRONT EXTENDING NORTHEAST FROM THE AKPEN LOW IS CURRENTLY BRINGING
LIGHT RAIN TO THE SOUTHERN KENAI PENINSULA.  ON THE BACKSIDE OF THIS
LOW...NEAR GALE FORCE WINDS ARE BEING REPORTED IN THE ALEUTIANS
WHILE COLDER AIR IS FILTERING INTO THE BERING.  THESE TWO LOWS WILL
MERGE LATE TOMORROW IN THE SOUTHWEST GULF AND BECOME A MAJOR PLAYER
IN OUR WEATHER THROUGHOUT THE WEEK.

.MODEL DISCUSSION...
ALOFT...ALL MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH THURSDAY. THE
LOW CURRENTLY DIGGING OUT THE THE ARCTIC WILL COMBINE WITH THE AKPEN
LOW TO FROM A LARGE UPPER LEVEL CLOSED LOW SOUTH AND WEST OF THE GULF
ON THURSDAY.  AN IMPRESSIVE 190 KT UPPER LEVEL JET WILL HELP CARVE
THIS OUT AND SET THE STAGE FOR A POWERFUL STORM THURSDAY INTO FRIDAY.
AT THE SURFACE...THE VERTICALLY STACKED AKPEN LOW WILL MEANDER IN
THIS REGION BEFORE A POWERFUL LOW MOVES NEAR THE SOUTHWEST GULF ON
THURSDAY.  AT THIS TIME IT APPEARS THAT THE LOW WILL DEEPEN INTO THE
960S EARLY THURSDAY MORNING BEFORE FILLING IN AS IT MOVES NORTH AND
EAST.  WE LIKE HOW THE ECMWF IS HANDLING THE STORM AND ARE TRENDING
TOWARDS ITS SOLUTION DURING THE LATTER HALF OF THE WEEK.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
LIGHT RAIN IS CURRENTLY MOVING INTO PORTIONS OF THE KENAI PENINSULA
TONIGHT WHILE CLOUDS ARE ON THE INCREASE THROUGHOUT MUCH OF
SOUTHCENTRAL. EXPECT THIS ACTIVITY TO MOVE NORTH AND EAST THROUGHOUT
THE DAY TODAY. WITH THE EASTERLY FLOW ALOFT EXPECT AREAS THAT SIT ON
THE WESTERN SIDES OF MOUNTAINS TO EXPERIENCE DOWNSLOPING THAT WILL
MINIMIZE THE AMOUNT OF RAINFALL. THIS FRONT SHOULD HIT THE SOUTHERN
COAST WEDNESDAY BUT SHOULD NOT PENETRATE TOO FAR INLAND. THE NEXT
SYSTEM MOVES INTO THE GULF WEDNESDAY NIGHT INTO THURSDAY BRINGING
ALONG GALE TO STORM FORCE WINDS. IT LOOKS AS THOUGH THE STORM SHOULD
REACH MAXIMUM STRENGTH EARLY THURSDAY AND THEN WEAKEN AS IT MOVES
NORTH AND EAST TO THE SOUTHERN COAST. KODIAK ISLAND LOOKS TO BE AN
AREA OF CONCERN FOR HIGH WIND DUE TO ITS RELATIVE CLOSE PROXIMITY TO
THE STORM THURSDAY MORNING. EVEN MORE IMPORTANT...THE WATERS OF THE
GULF LOOK TO BE QUITE TREACHEROUS DURING THIS TIME FRAME.

.SOUTHWEST...
AREAS OF LIGHT PRECIPITATION ARE OVER PARTS THE AKPEN AND SOUTHERN
AREAS OF SOUTHWEST ALASKA THIS MORNING.  AS MENTIONED EARLIER...THE
LOW SOUTH OF THE AKPEN WILL COMBINE WITH THE LOW THAT IS CURRENTLY
DIGGING OUT OF THE ARCTIC.  DURING THIS TIME FRAME THE REGION WILL
REMAIN UNDER A CYCLONIC FLOW WITH SEVERAL SHORTWAVES ROTATING THROUGH
THE AREA TILL WEDNESDAY NIGHT.  EXPECT THIS TO BRING SHOWERS AND
CLOUDS TO THE AREA UNTIL THEN.  THURSDAY...A NORTHERLY FLOW BEGINS TO
DEVELOP AS THE UPPER LEVEL LOW SHIFT INTO THE GULF.  THIS WILL HELP
DRY OUT MOST OF THE REGION DURING THE LATTER HALF OF THE WEEK.

.BERING SEA AND ALEUTIANS...
A NORTHERLY FLOW BRINGING GALE FORCE WINDS HAS SET IN FOR MOST OF THE
EASTERN BERING AS THE LOW HAS SHIFTED OFF TO THE EAST. COLDER AIR IS
FILTERING INTO THE REGION AND WILL KEEP STRONG NORTH WINDS PERSISTENT
THOUGH WEDNESDAY. AFTER THIS ALL EYES FOCUS ON FORMER TROPICAL STORM
DUJUAN.  LAST NIGHT MODELS HAD A MUCH BETTER HANDEL ON THE SITUATION
BUT NOW THEIR SOLUTIONS BEGIN TO DIVERGE. THE ECMWF IS STILL
CONSISTENT OF TAKING A RELATIVELY STRONG STORM (960S MB) WEST OF ATTU
WHILE THE GFS IS TAKING A MUCH WEAKER STORM (980S MB) TO THE CENTRAL
ALEUTIANS THURSDAY.  CURRENT THINKING IS TO USE THE ECMWF AS IT HAS
BEEN MUCH MORE CONSISTENT OVER THE PAST SEVERAL DAYS...HOWEVER...THIS
WILL NEED TO BE CLOSELY WATCHED AS THERE IS STILL MUCH UNCERTAINTY
OVER THIS POTENTIALLY STRONG STORM.

.LONG TERM FORECAST...
THE FLOW BECOMES MORE ZONAL LATER IN THE WEEK AS THERE IS GENERAL
AGREEMENT OF MOVING A NEW UPPER LEVEL LOW TO THE BRISTOL BAY REGION
SATURDAY AND THEN SOUTH OF THE GULF BY MONDAY. IF THIS PATTERN PANS
OUT EXPECT MOSTLY CLOUDY SKIES WILL SOME PRECIPITATION FOR THE
EXTENDED.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE WARNING ZONES 165 170 171 172 179 180 185 412 413 414
FIRE WEATHER...NONE

WILSON SEP 09