Gale Warning 695, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
325 PM AKST FRI NOV 21 2008

.ANALYSIS AND UPPER LEVELS...
A VERY ACTIVE WEATHER PATTERN ACROSS THE STATE TODAY WITH MULTIPLE
VORTICIES EVIDENT ON THE WATER VAPOR IMAGERY. THE MOST IMPRESSIVE IS
LOCATED OVER THE KUSKOKWIM VALLEY WITH A STRONG SHORTWAVE CROSSING
THE ALASKA/CANADA BORDER NEAR EAGLE AND A SECOND WEAKER WAVE ALONG
THE NORTHEASTERN GULF COAST BETWEEN CORDOVA AND YAKUTAT. TO THE
WEST...A LARGE VERTICALLY STACKED LOW LOCATED NEAR THE PRIBILOF
ISLANDS IS WEAKENING AS IT BECOMES ABSORBED BY THE DOMINANT LONG WAVE
LOW OVER THE MAINLAND. AT THE SURFACE...THERE ARE SEVERAL KEY
FEATURES THAT WILL BE IMPORTANT IN THE UPCOMING FORECAST. THE MOST
CRITICAL IS A TRIPLE POINT LOW THAT IS DEVELOPING ALONG THE OCCLUSION
OVER THE ALASKA PENINSULA. IN THE GULF...THERE IS A WEAK LOW LOCATED
NEAR MIDDLETON ISLAND THAT IS INTERACTING WITH AN UPPER LEVEL
SHORTWAVE....PRODUCING NUMEROUS SHOWERS ALONG THE COAST AND
COMPLICATING THIS EVENINGS FORECAST FOR THE WESTERN KENAI AND
ANCHORAGE BOWL.

.MODEL DISCUSSION...
THE LARGE AREA OF LOW PRESSURE OVER THE WESTERN HALF OF THE STATE
WITH MULTIPLE EMBEDDED SHORTWAVES IS NOT BEING ACCURATELY DEPICTED BY
ANY OF THE 4 MODELS WE EVALUATED. OVERALL THERE IS RELATIVE AGREEMENT
ON THE SYNOPTIC FEATURES THROUGH 60 HOURS BUT TIMING AND STRENGTH IN
THE SHORT WAVES...WHICH TRANSLATES TO DISCREPANCIES IN THE SURFACE
FEATURES...WILL HAVE THE LARGEST IMPACT ON THE FORECAST THROUGH THE
WEEKEND. GIVEN ALL OF THESE UNCERTAINTIES...OUR CONFIDENCE IS NOT
HIGH IN SOME OF THESE KEY FEATURES THAT WILL BE DISCUSSED.

THE NAM HAS HAD THE WORST TRACK RECORD LATELY AND IS VARYING THE MOST
FROM RUN TO RUN WHILE THE GFS IS SHOWING IMPROVED RUN TO RUN
CONTINUITY. WE LEANED TOWARD THE 12Z GFS RUN FOR THIS FORECAST
PACKAGE.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
WHILE THE GAP WINDS HAVE DIMINISHED FROM PREVIOUS DAYS...SEVERAL
AREAS ARE STILL SEEING STRONG WINDS AS A RESULT OF THE LOW PRESSURE
SYSTEM IN THE GULF AND THE ARCTIC AIRMASS OVER THE INTERIOR. THE MOST
IMPRESSIVE FEATURE IS ASSOCIATED WITH THE GAP WINDS FLOWING OUT OF
KAMISHAK BAY AND BY THE BARREN ISLANDS. A MESO-LOW HAS DEVELOPED
SOUTH OF SEWARD.  THIS SUBTLE FEATURE COUPLED WITH A SHORTWAVE MOVING
UP COOK INLET IS RESULTING IN A BAND OF SNOW FROM HOMER UP TO KENAI
AND INTO THE SOUTHERN SUSITNA VALLEY. SNOWFALL FROM THIS FEATURE WILL
REMAIN LIGHT AS THERE IS VERY LITTLE MOISTURE TO WORK WITH.

THE TRIPLE POINT LOW NEAR THE ALASKA PENINSULA DEVELOPS AND MOVES
SOUTHEAST OF KODIAK AND INTO WESTERN PRINCE WILLIAM SOUND SATURDAY.
UPPER LEVEL SUPPORT IS LACKING WITH THIS LOW AS IS THE THERMAL
PACKING WE LIKE TO SEE AT 850 MB. WHILE WE ARE STILL CALLING FOR SNOW
IN THE ANCHORAGE AREA SATURDAY...IT SHOULD REMAIN LIGHT. SATURDAY
NIGHT IS LOOKING MORE AND MORE LIKE A FAVORABLE SETUP FOR
ACCUMULATING SNOW IN SOUTHCENTRAL WITH THE AFOREMENTIONED FEATURES
ALL NICELY COMING TOGETHER. AT THIS POINT...WILL BE CALLING FOR 2 TO
4 INCHES FOR THE WESTERN KENAI AND ANCHORAGE BOWL AND LOWER AMOUNTS
IN THE MATANUSKA AND SUSITNA VALLEYS. IF SUBSEQUENT MODEL RUNS
CONTINUE ADVERTISING THIS SCENARIO...WILL HAVE TO TREND THE SNOW
AMOUNTS UP.

SOUTHWEST ALASKA...
CLEAR AND COLD WEATHER PERSISTS OVER THE SOUTHWEST INTERIOR WITH THE
EXCEPTION BEING THE UPPER KUSKOKWIM VALLEY. RECORD LOW TEMPERATURES
HAVE BEEN SET FOR THIS DATE IN BETHEL AND KING SALMON...THE 3RD DAY
IN A ROW FOR BETHEL.

A DEFORMATION ZONE STRETCHING NORTHWEST TO SOUTHEAST IS PROVIDING
JUST ENOUGH LIFT TO SQUEEZE MOISTURE OUT OF THE CLOUDS NEAR MCGRATH.
THE LIGHT SNOW FALL IS LETTING UP ALREADY THIS AFTERNOON AS THE AXIS
SHIFTS TO THE EAST AND NORTH.

THE BIGGEST CONCERN FOR THIS AREA IS THE NEAR RECORD COLD
TEMPERATURES AND BITTER WIND CHILL READINGS ALONG THE COAST OF THE
KUSKOKWIM DELTA. STRONGEST WINDS ARE ALONG THE COAST BRINGING WIND
CHILL READINGS NEAR ADVISORY CRITERIA LEVEL. 25-35 BELOW ZERO WIND
CHILL READINGS ARE LIKELY TO CONTINUE THROUGH TOMORROW WITH A
REINFORCING SHOT OF COLD AIR MOVING SOUTH TONIGHT.

OTHERWISE...SURFACE HIGH PRESSURE WILL REMAIN IN CONTROL RESULTING IN

CLEAR AND COLD WEATHER THROUGH SUNDAY MORNING. A FRONTAL BOUNDARY
APPROACHING BRISTOL BAY AND THE KUSKOKWIM DELTA COULD POTENTIALLY
RESULT IN BLIZZARD CONDITIONS ALONG THE COAST AS EARLY AS SUNDAY
EVENING. THIS IS ONE FEATURE THAT THE MODELS ARE HAVING A HARD TIME
HANDLING SO WILL NOT RUSH TO ANY WATCHES AT THIS TIME. THIS WILL HAVE
TO BE WATCHED AS MODELS CONVERGE ON A SOLUTION THIS WEEKEND.

BERING SEA ALEUTIANS...
THE FORECAST CHALLENGE FOR THE FIRST 48 HOURS WILL BE THE WEAKENING
LOW NEAR THE PRIBILOF ISLANDS. STORM FORCE WINDS WILL DIMINISH TO
GALES LATER TONIGHT AS THE LOW SAGS SOUTHEAST TOWARD THE ALASKA
PENINSULA. A NORTH PACIFIC LOW WILL DEEPEN RAPIDLY THIS WEEKEND FROM
990 MB TO 968 MB IN 24 HOURS. THIS WILL BRING STORM FORCE WINDS BACK
TO THE CENTRAL AND WESTERN BERING SEA BY SUNDAY ON THE COLD AIR
ADVECTION SIDE OF THE LOW. THE FRONTAL BOUNDARY ASSOCIATED WITH THIS
LOW COULD POSSIBLY BRING BLIZZARD CONDITIONS TO THE PRIBILOFS
SATURDAY NIGHT.

.LONG TERM FORECAST...
COPIED FROM THE PREVIOUS FORECAST DISCUSSION...
A VERY PROGRESSIVE HEMISPHERIC PATTERN WITH A STRONG SUB-TROPICAL JET
WILL LEAD TO A VERY STORMY EXTENDED PERIOD WITH RAPIDLY CHANGING
CONDITIONS ACROSS THE FORECAST AREA. THIS WILL MAKE IT VERY DIFFICULT
TO FORECAST THE DETAILS OF THESE STORMS VERY FAR OUT IN TIME.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...185.
         GALE WARNING...155 165 170 171 172 175 176 179 180.
         HEAVY FREEZING SPRAY...160 180.
FIRE WEATHER...NONE.

AB NOV 08