Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 222342
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
242 PM AKST MON DEC 22 2014

.DISCUSSION...

EVEN THOUGH QUIET WEATHER IS EXPECTED ACROSS MOST OF NORTHERN
ALASKA THROUGH WEDNESDAY MORNING...THERE ARE A FEW FORECAST
CONCERNS INCLUDING STRATUS OVER THE WESTERN TWO-THIRDS OF ALASKA
AND THE YUKON AND CHANCES FOR SNOW SHOWERS OVER PARTS OF THE
INTERIOR THROUGH WEDNESDAY AFTERNOON.

IN REGARDS TO THE 12Z DETERMINISTIC MODEL GUIDANCE...THERE IS
FAIRLY GOOD AGREEMENT AMONGST THE MODELS THROUGH 12Z WEDNESDAY.
AFTER 12Z WEDNESDAY...SIGNIFICANT DIFFERENCES BETWEEN THE ECWMF
AND THE GFS/GEFS/NAM ON THE KEY SYNOPTIC FEATURES DEVELOP AND
BECOME WORSE DURING THE EXTENDED.

ALOFT...

COLD UPPER LEVEL TROUGH EXTENDS FROM A WEAK LOW OVER THE NEW
SIBERIAN ISLANDS SOUTHEAST OVER THE CHUKOTSK AND SEWARD PENINSULAS
AND BEAUFORT SEA. THIS TROUGH WILL DEEPEN AS IT MOVES EAST OVER
THE NORTHERN HALF OF ALASKA THROUGH LATE THIS WEEK. COINCIDENT
WITH THIS TROUGH...A COLDER AIRMASS WILL BE MOVING EASTWARD. THE
COLDEST AIR AT H850...AROUND -20C...WILL BE CONTAINED TO NORTH OF
THE BROOKS RANGE AND AT THE SURFACE...A 10F TO 15F DROP IN
TEMPERATURES FROM WHAT WAS SEEN LAST NIGHT. LOCATIONS SOUTH OF
THE BROOKS RANGE WILL SEE TEMPERATURES COOLING TO NEAR NORMAL
TUESDAY AND WEDNESDAY.

AFTER 12Z WEDNESDAY...DETAILS BECOME A BIT FUZZY SINCE MODEL
SOLUTIONS GREATLY DIFFER. EVEN THOUGH THIS IS THE CASE...THERE IS
A GENERAL CONSENSUS THAT AN UPPER LEVEL RIDGE WILL BUILD NORTH
FROM THE BERING SEA AND OVER MAINLAND ALASKA FOLLOWING THE PASSAGE
OF THE AFOREMENTIONED TROUGH. CONCERNING THE AFOREMENTIONED TROUGH
AFTER 12Z WEDNESDAY...THE GFS IS MORE PROGRESSIVE WITH MOVING IT
EAST...WHILE THE ECWMF HOLDS IT BACK...KEEPING A BROAD UPPER LEVEL
TROUGH OVER WESTERN ALASKA BEFORE LIFTING IN NORTHEAST LATE THIS
WEEK.

AN UPPER LOW WILL DEVELOP EAST OF KAMCHATKA PENINSULA BY 06Z
WEDNESDAY AND GRADUALLY DRIFT EAST INTO THE BERING. SIMILAR TO
OTHER UPPER LEVEL FEATURES MENTIONED...THE GFS AND ECWMF HANDLE
THE PROGRESSION OF THIS LOW DIFFERENTLY BEYOND 12Z WEDNESDAY.
HOWEVER...BOTH MODELS DO SHOW MULTIPLE SHORTWAVES ROUNDING THE
BASE OF THIS LOW AND MOVING NORTHEAST TOWARDS THE WEST COAST.
THOUGH TIMING OF THESE SHORTWAVES IS UNCERTAIN GIVEN MODEL
DISAGREEMENT.

SURFACE...

1008MB SURFACE LOW LOCATED 140 MILES NORTHWEST OF BARROW AT 18Z IS
PROGGED TO MOVE NORTHWEST TOWARDS THE NEW SIBERIAN ISLANDS THROUGH
MIDWEEK. THE WEAK 1009MB LOW OVER PRINCE WILLIAM SOUND WILL MERGE
INTO A NORTHWARD MOVING 990MB LOW FROM THE NORTHERN PACIFIC. THE
RESULTING LOW WILL MOVE EAST AND OVER THE SOUTHEAST AK PANHANDLE.

OVER THE BERING...A STRONG LOW WILL MOVE TO NEAR SHEMYA BY 12Z
TUESDAY. AN OCCLUSION STRETCHING FROM THIS LOW WILL ROTATE EAST
OVER THE ALEUTIAN ISLANDS WEDNESDAY AND THEN NORTHEAST ALONG THE
ALASKA PENINSULA AND SOUTHWEST COAST BY 00Z THURSDAY. POSSIBLE
HAZARDS POSSIBLY ASSOCIATED WITH THIS LOW WILL BE GALE TO STORM
FORCE WINDS DEVELOPING WEDNESDAY NIGHT OVER ST LAWRENCE AND BERING
STRAIT AND A MESSY WINTRY MIX OF SNOW/FREEZING RAIN/RAIN OVER THE
SOUTHWEST...WHERE WARM AIR ADVECTION ALOFT AHEAD OF THE FRONT WILL
CREATE SOME ISSUES WITH PRECIPITATION TYPE STARTING AFTER 00Z
THURSDAY FOR ST LAWRENCE ISLAND AND THE YUKON DELTA.

MORNING AND EARLY IMAGES FROM THE SPORT MICROPHYSICS RGB
PRODUCT...SHOWS A BLANKET OF STRATUS OVER THE WESTERN TWO-THIRDS
OF ALASKA THAT IS GRADUALLY INCREASING IN AREAL EXTENT OVER
EASTERN ALASKA THIS AFTERNOON. THE PRESENCE OF STRATUS WILL
GREATLY IMPACT OVERNIGHT TEMPERATURES...KEEPING TEMPERATURES
WARMER THAN OTHERWISE WOULD BE WITHOUT STRATUS AND COLDER H850
TEMPERATURES.

IN REGARDS TO PRECIPITATION...AS THE AFOREMENTIONED UPPER LEVEL
TROUGH SHIFTS EAST OVER NORTHERN ALASKA...PERIODS OF SNOW DEVELOP
OVER THE CENTRAL/EASTERN INTERIOR AND EASTERN ARCTIC COAST TUESDAY
MORNING AND THEN GRADUALLY SHIFT EAST THROUGH THURSDAY. SNOW
ACCUMULATIONS WILL RANGE FROM A DUSTING UP TO 2 INCHES...WITH
POSSIBLE IMPACTS TO THE PUBLIC BEING HAZARDOUS ROAD CONDITIONS
ALONG THE HIGHWAYS.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
HEAVY FREEZING SPRAY WARNING FOR PKZ210.

&&

$$

LTH DEC 14


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