FXAK69 PAFG 071425
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
525 AM AKST MON DEC 7 2009

.DISCUSSION...
THE GFS AND NAM MODELS BOTH FORECAST THE STRONG HIGH PRESSURE AREA
ALOFT TO BUILD FROM THE NORTH GULF OF ALASKA COAST UP OVER THE
ALASKA MAINLAND AND TO REMAIN THROUGH WEDNESDAY AND BEYOND. BOTH
FORECAST A SHORT WAVE ALOFT TO MOVE RAPIDLY NORTHWARD ALONG THE
BERING SEA COAST TONIGHT. THIS IS EXPECTED TO CAUSE THE SOUTHEAST
GALES OVER THE EAST BERING SEA TO REJUVENATE TONIGHT AFTER A SMALL
DECREASE TODAY. THIS DEVELOPMENT AND ITS TIMING HAVE BEEN
CONSISTENTLY FORECAST BY THE MODELS FOR AT LEAST 2 DAYS AND LOOK
CREDIBLE. FOR THIS REASON...THE GALES OVER PKZ WEST OF SAINT
LAWRENCE ISLAND HAVE BEEN FORECAST TO CONTINUE THROUGH TUESDAY.

THE INFLOW OF WARM AIR ALOFT OVER NEARLY ALL OF THE REALM IS
UNUSUALLY STRONG FOR THIS TIME OF YEAR. FREEZING DRIZZLE GOT AS
FAR EAST AS FAIRBANKS ON SUNDAY AND AS FAR NORTH AS KOTZEBUE
SUNDAY NIGHT. PRUDHOE BAY HAD BRIEF FREEZING RAIN SUNDAY MORNING.
THERE MAY BE ISOLATED AREAS OF FREEZING DRIZZLE AS FAR UP AS
BARROW AND PRUDHOE BAY TODAY AND TONIGHT.

EARLY MORNING POLAR ORBITING SATELLITE IMAGERY SHOWS A SOLID BAND 
OF CLOUDS EXTENDING FROM THE SEWARD PENINSULA TO THE CENTRAL
ALASKA RANGE. SO FAR...NEITHER SURFACE REPORTS NOR THE FAIRBANKS
RADAR HAVE PICKED UP ANY PRECIPITATION WITH THIS FEATURE. SOME
THINNER BANDS OF CLOUDS BROUGHT SOME FLURRIES TO THE NORTHEAST
INTERIOR DURING THE NIGHT. EAGLE PICKED UP .02 INCHES OF
PRECIPITATION...BETTLES MEASURED .03 INCHES. THUS...THE INCOMING
BAND OF CLOUDS MAY SET OFF SOME FLURRIES IN THE SAME AREA TODAY.

THE WARM AIR ALOFT...FLOWING OVER THE COLD AIR IN THE BOUNDARY
LAYER IS A REASONABLE PATTERN FOR PRECIPITATION FOR NORTHEAST
ALASKA. IT ALSO IS THE REASON FOR THE VAST RANGE OF TEMPERATURES
FORECAST BETWEEN THE VALLEY FLOOR AND THE UPLANDS THROUGHOUT
NORTHERN ALASKA. 

THE ABNORMALLY WARM TEMPERATURES THROUGHOUT NORTHERN ALASKA...WITH
THE EXCEPTION OF THE INTERIOR EAST OF BETTLES AND BIG DELTA...HAS
MOISTENED THE BOUNDARY LAYER. NOW THAT CLEARING IS UNDERWAY
STARTING IN SOUTHWEST ALASKA...THERE WILL BE A FEW AREAS OF FOG AS
TEMPERATURES INEVITABLY FALL AS THE CLOUDS MOVE AWAY. 

THE PROLONGED SOUTHEAST GALES OVER THE BERING SEA MAY HAVE CAUSED
THE PACK ICE EDGE TO RETREAT SOME TOWARD SAINT LAWRENCE ISLAND
OVER THE WEEKEND. IF THIS HAS OCCURRED TO A SUFFICIENT
EXTENT...FORECASTS FOR SEAS WILL BE RESUMED IN PKZ210.

MOVING BEYOND WEDNESDAY...THE GFS MODEL FORECASTS THE HIGH ALOFT
TO ELONGATE ON AN AXIS FROM CHUKOTKA TO BERING STRAIT DOWN THROUGH
MCGRATH. STARTING THURSDAY...THE GFS FORECASTS A FAIRLY STRONG
SURGE OF ARCTIC AIR TO BEGIN OVER NORTHEAST ALASKA. BY
SATURDAY...THE GFS FORECASTS 850 MB TEMPERATURES OVER THE ARCTIC
AND THE NORTHERN AND EASTERN INTERIOR TO BE A REMARKABLE 15 TO 28
DEGREES C /25 TO 52 DEGREES F/ COLDER THAN THEY ARE TODAY. THE
GREATEST COOLING WILL BE OVER THE EASTERN BROOKS RANGE. SINCE THIS
ARCTIC OUTBREAK COMES FROM THE NORTH IT IS EXPECTED TO PRODUCE
VERY LITTLE PRECIPITATION. THE SNOWPACK IN MOST OF NORTHERN ALASKA
IS ABNORMALLY LIGHT SO FAR THIS SEASON.

LOOKING AT THE MEDIUM RANGE FORECASTS...THE GFS AND EUROPEAN
MODELS HAVE BEEN SWAPPING FORECASTS FOR AT LEAST 2 DAYS. THIS
CONSIDERABLY LOWERS THE CONFIDENCE FACTOR FOR FORECASTS BEYOND
WEDNESDAY.

TODAY...THE GFS FORECASTS GREATER COOLING OVER EASTERN ALASKA
THAN THE EUROPEAN MODEL...STARTING ON FRIDAY THIS WEEK AND ALL THE
WAY THROUGH WEDNESDAY OF THE FOLLOWING WEEK. YESTERDAY...THE GFS
WAS RESTRAINED ON THE FORECAST COOLING WHILE THE EUROPEAN MODEL WAS
MORE AGGRESSIVE. THE MODEL OUTPUT STATISTICS FORECASTS CONTINUE TO
INDICATE VERY LITTLE COOLING THROUGH THIS WEEK. THIS DOES NOT LOOK
REASONABLE REGARDLESS OF THE MODEL CHOSEN. THUS...TEMPERATURES IN
THIS MORNINGS ZONE FORECASTS FOR EASTERN ALASKA AT THE END OF THIS
WEEK ARE CONSIDERABLY COLDER THAN THE NUMERICAL GUIDANCE. THE
MODEL OUTPUT STATISTICS APPEAR TO GIVE TOO GREAT A WEIGHT TO
CLIMATOLOGY AND TOO LITTLE TO THE FORECASTS OF CIRCULATION
FEATURES. 

ONE PART OF THE FORECASTS HAS A HIGH CONFIDENCE FACTOR. THIS IS
FOR THE DECREASE IN WIND OVER THE BERING SEA COAST STARTING
TUESDAY. BY WEDNESDAY...WINDS OUT THERE AND OVER THE REST OF
NORTHERN ALASKAS COASTAL WATERS ARE EXPECTED TO BE QUITE LIGHT.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FOR PKZ210.

BRISK WIND ADVISORY FOR PKZ200.
&&

$$

TF DEC 09