Blizzard in Alaska, November 24, 2009

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKST MON NOV 23 2009

.ANALYSIS/UPPER LEVELS...COMPLEX PATTERN CONTINUES WITH A BROAD LOW
OVER THE CENTRAL BERING SEA WITH MULTIPLE STRONG WAVES ROTATING
AROUND ITS PERIPHERY. THE FIRST STORM IS MOVING ONSHORE EARLY THIS
AFTERNOON...A 971 MB LOW OVER THE SOUTHERN TIP OF THE KENAI
PENINSULA. THE NEXT STORM IS STILL DEVELOPING AROUND 45N AND WILL
EVENTUALLY TURN NORTH TONIGHT AND WEAKEN AS IT APPROACHES THE GULF. A
THIRD WAVE WHICH IS A LITTLE MORE SUBTLE IS JUST SPINNING UP OVER THE
WESTERN BERING SEA.

.MODEL DISCUSSION...MODELS IN EXCELLENT AGREEMENT REGARDING THE FIRST
LOW MOVING INLAND TODAY. THE WINDS ASSOCIATED WITH THE SHIFT IN THE
GRADIENT ARE ALSO ALL WELL COVERED IN THE CURRENT FORECAST. ATTENTION
TURNS TO THE NEXT STORM DEVELOPING IN THE NORTH PACIFIC. THE
GFS...UKMET...AND ECMWF ARE IN FAIR AGREEMENT WITH THIS SYSTEM
LEAVING THE NAM AS THE OUTLIER. THE CONSENSUS IS FOR THE SYSTEM TO
DEVELOP A SECONDARY AREA OF LOW PRESSURE THAT WILL ROTATE AROUND INTO
THE NORTHERN GULF BY TUESDAY EVENING. A NICE DEFORMATION ZONE WILL
SET UP AHEAD OF A POTENT SHORTWAVE MOVING ACROSS THE ALASKA RANGE AND
UP COOK INLET WEDNESDAY AFTERNOON. WHAT THE MODELS DIFFER ON IS THE
EXTENT OF THE MOISTURE BEING THROWN OVER THE CHUGACH RANGE AND WHERE
EXACTLY THE DEFORMATION ZONE SETS UP. FOR THIS FORECAST
PACKAGE...LEANED TOWARD THE WETTER SOLUTION OF THE GFS/ECMWF THAT
WOULD PUT SNOW BACK IN ANCHORAGE SOMETIME WEDNESDAY.

OUT WEST...LARGE DIFFERENCES ARISE ON THANKSGIVING DAY WHEN A SERIES
OF LOWS EVENTUALLY DEVELOP INTO ANOTHER LARGE 970ISH LOW NEAR BRISTOL
BAY. THE LATEST ECMWF IS NOW ABOUT 12 HOURS BEHIND WHERE THE GFS HAS
BEEN CONSISTENTLY PUTTING THIS LOW BY THURSDAY EVENING. THIS FORECAST
PACKAGE WILL LEAN TOWARD THAT NEW GFS SOLUTION BUT CONFIDENCE IS LOW
WITH THIS SYSTEM.

.SHORT TERM FORECAST...
SOUTHCENTRAL...HIGH WIND WARNING FOR TURNAGAIN ARM TO BEGIN IN A
COUPLE HOURS IS STILL LOOKING GOOD. 971 MB LOW PRESSURE MOVING UP
COOK INLET WILL EVENTUALLY SHIFT THE PRESSURE GRADIENT TO ALLOW THE
STRONGEST WINDS TO FUNNEL THROUGH TURNAGAIN ARM. SOME OF THESE WINDS
WILL BEND NORTHWARD AND MAKE IT INTO ANCHORAGE...RESULTING IN A GUSTY
EVENING WITH WINDS 25 TO 40 MPH IN TOWN...STRONGEST ALONG THE INLET.
WEST OF THE CHUGACH RANGE SHOULD STAY MOSTLY DOWNSLOPED DURING THIS
EVENT...ONLY EXPECTED SCATTERED RAIN AND SNOW SHOWERS THIS AFTERNOON
AND EVENING...UNTIL THE PRESSURE GRADIENT AGAIN BECOMES ORIENTED
NORTH/SOUTH AS THE NEXT LOW MOVES INTO THE GULF.

SOUTHWEST...UPPER LOW AND ASSOCIATED DEFORMATION ZONE SLOWLY MAKING
PROGRESS ACROSS SOUTHWEST ALASKA RESULTING IN SNOW FROM BRISTOL BAY
UP TO THE LOWER KUSKOKWIM VALLEY. THE DEFORMATION MOVES
INLAND...ALLOWING FOR MOIST SOUTHWEST WINDS TO USHER IN FOG AND
SHOWERS THROUGH TONIGHT AND TUESDAY. HIGH PRESSURE BRIEFLY BUILDS
TUESDAY NIGHT AND WEDNESDAY MORNING BEFORE THE NEXT SYSTEM APPROACHES
THE COAST WEDNESDAY EVENING.

ALEUTIANS/BERING SEA...COLD AIR ADVECTING OVER THE RELATIVELY WARM
BERING SEA WATERS IS RESULTING IN WIDESPREAD SHOWER ACTIVITY. THE
COMBINATION OF GUSTY WINDS AND SNOW SHOWERS WILL OCCASIONALLY REDUCE
VISIBILITY LESS THAN ONE HALF MILE ALL ALONG THE
ALEUTIANS...INCLUDING THE PRIBILOFS. LONG WAVE TROUGH DOES NOT MAKE
MUCH PROGRESS SO SHOWER ACTIVITY WILL PERSIST THROUGH THE REMAINDER
OF THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131
         HIGH WIND WARNING 101
MARINE...STORM 175 176
        GALES 120 130 132 150 155 170 172 185
FIRE WEATHER...NONE

AB NOV 09