FXAK68 PAFC 252311
AFDAFC

AREA FORECAST DISCUSSION 
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKST WED NOV 25 2009

.ANALYSIS/UPPER LEVELS...
LONG WAVE PATTERN REMAINS UNCHANGED WITH BROAD TROUGH CENTERED OVER
THE EASTERN BERING SEA. MULTIPLE WAVES ROTATING AROUND THE CYCLONIC
CIRCULATION...THE MOST SIGNIFICANT TWO ARE LOCATED OVER THE NORTHERN
GULF AND A MORE POWERFUL STORM LOCATED JUST SOUHTWEST OF THE PRIBILOF
ISLANDS. 

AT THE SURFACE...THE TWO MAIN FEATURES ASSOCIATED WITH THESE WAVES IS
AN ELONGATED 981 MB LOW MOVING INTO THE NORTHERN GULF...SPREADING
SNOW FROM PRINCE WILLIAM SOUND BACK TOWARD THE KENAI PENINSULA AND
THE SECOND LOW VERTICALLY STACKED UNDER THE UPPER FEATURE...BUT THERE
ARE SEVERAL MESO LOWS LOCATED ALONG THE FRONTAL BOUNDARY EXTENDING
SOUTHEAST TOWARD THE ALASKA PENINSULA. STRONG WINDS AND A MIX OF RAIN
AND SNOW CAN BE FOUND ALL ALONG THIS BOUNDARY WITH NUMEROUS SHOWERS
ON THE BACKSIDE.

.MODEL DISCUSSION...MODELS ARE STRUGGLING WITH THIS PATTERN AS RUN TO
RUN CONSISTENCY IS VERY POOR LEADING TO LOW CONFIDENCE BEYOND THE
FIRST 48 HOURS. THE LOW IN THE GULF DID NOT INITIALIZE VERY WELL. IT
APPEARS TO BE LOCATED WEST OF WHERE THE MODELS THINK IT SHOULD BE AND
HEADING TOWARD SEWARD INSTEAD OF MONTAGUE ISLAND. THIS IS SIGNIFICANT
BECAUSE A MORE WESTWARD TRACK WILL RESULT IN A BETTER CHANCE OF SNOW
IN ANCHORAGE THIS EVENING. 

FOCUS TURNS TO THE NEXT DEVELOPING WAVE THURSDAY AFTERNOON AROUND
KODIAK AND THE ALASKA PENINSULA. MODEL SOLUTIONS HAVE BEEN VERY
DIFFERENT WITH THESE FEATURES OVER THE PAST SEVERAL RUNS. WE CONTINUE
TO LEAN TOWARD THE ECMWF WHICH HAS THE INITIAL LOW WEAKENING AND
MOVING ONSHORE NEAR PORT HEIDEN WHILE A SECONDARY LOW DEVELOPS
SOUTHEAST OF KODIAK AND MOVES UP COOK INLET THURSDAY NIGHT. THE
DIFFERENCES IN THE MODELS IS SIGNIFICANT BECAUSE THE 12Z GFS/NAM
SOLUTION WOULD BRING HIGH WIND WARNING WINDS TO TURNAGAIN ARM AND THE
PORTAGE AREA THURSDAY EVENING WHILE THE UKMET/ECMWF WOULD RESULT IN A
VERY SIMILAR FORECAST FROM THE STORM EARLIER IN THE WEEK...STRONG
WINDS BUT NOT QUITE WARNING CRITERIA. 

.SHORT TERM FORECAST...
STILL EXPECTING SNOW WITH THE FIRST STORM TO AFFECT SOUTHCENTRAL
TONIGHT. THE MODELS HAVE PRODUCED SNOW FALL TOTALS RANGING FROM
ALMOST A FOOT TO ZERO IN THE LAST COUPLE OF RUNS. OUR CURRENT
FORECAST OF 1 TO 4 INCHES IS STILL LOOKING VERY REASONABLE GIVEN THE
UNCERTAINTY AND THE CURRENT TRENDS. SNOW WILL SPREAD ACROSS THE
ANCHORAGE BOWL LATE THIS AFTERNOON AND THROUGH THIS EVENING. THE MORE
SIGNIFICANT ACCUMULATING SNOW FALL IS EXPECTED LATER THIS EVENING AS
THE UPPER WAVE APPROACHES...AND EVENTUALLY TAPERING OFF BY MORNING. 

THE NEXT SYSTEM RAPIDLY DEVELOPS AROUND KODIAK AND WINDS INCREASE TO
GALE FORCE ACROSS THE NORTHERN GULF BY THURSDAY AFTERNOON. THE
INCREASING PRESSURE GRADIENT ALONG THE COASTAL MOUNTAIN RANGE WILL
RESULT IN SOME GUSTY GAP WINDS...ESPECIALLY OF CONCERN IS THOMPSON
PASS WHERE FRESH SNOWFALL TONIGHT WILL EASILY BE PICKED UP AND BLOWN
AROUND. A BLIZZARD WATCH HAS BEEN ISSUED THURSDAY NIGHT FOR THAT AREA
SINCE WINDS ARE EXPECTED TO BE STRONG REGARDLESS OF WHERE THE LOW
ENDS UP.   

SOUTHWEST...DEFORMATION ZONE ALONG THE ALEUTIAN/ALASKA RANGE RESULTED
IN SOME LIGHT SNOW THIS MORNING...OTHERWISE SOUTHWEST ALASKA REMAINED
PARTLY CLOUDY. AREAS OF DENSE FOG HAS BEEN SLOW TO DISSIPATE UNDER
THE TRANSIENT UPPER RIDGE BETWEEN SYSTEMS. AS THE AFOREMENTIONED LOW
DEVELOPS TONIGHT...ANOTHER DEFORMATION ZONE WILL SET UP IN THE SAME
AREA BRINGING GENERALLY LIGHT SNOW FROM THE ALASKA PENINSULA UP TO
THE UPPER KUSKOKWIM VALLEY. 

ALEUTIANS/BERING SEA...THE MOST ACTIVE WEATHER REMAINS OUT WEST UNDER
THE BROAD UPPER TROUGH WITH WAVE AFTER WAVE DEVELOPING AND ROTATING
AROUND ITS PERIPHERY. THE LOW SOUTHWEST OF THE PRIBILOFS HAS A STRONG
SHORTWAVE DROPPING SOUTH ACROSS THE CENTRAL ALEUTIANS THIS EVENING. A
HIGH WIND WARNING HAS BEEN ISSUED FOR THIS AREA WITH GUSTS TO 75 MPH
THROUGH TONIGHT. A HIGH WIND WATCH WAS IN EFFECT FOR THE CENTRAL
ALEUTIANS BUT WAS CANCELLED. THE CORE OF THE STRONGEST WINDS WILL
STAY JUST WEST OF THE CENTRAL ALEUTIANS...ALTHOUGH LOCAL GUSTS TO 60
MPH ARE NOT OUT OF THE QUESTION AS THE SYSTEM ROTATES ACROSS
THURSDAY. ON FRIDAY...BROAD NORTHERLY FLOW SETS UP AND WILL PERSIST
THROUGH SATURDAY WHEN THE NEXT STRONG LOW DEVELOPS NEAR THE WESTERN
ALEUTIANS...POSSIBLY SPREADING STORM FORCE WINDS INTO THE CENTRAL
BERING SEA BY SATURDAY NIGHT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 187
         BLIZZAR WATCH 131
MARINE...STORM 170 172 
         GALES 120 130 132 150 155 175
         HEAVY FREEZING SPRAY 180 175
FIRE WEATHER...NONE

AB NOV 09