Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 021355
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
455 AM AKST MON MAR 2 2015

.DISCUSSION...

UPPER AIR...
AXIS OF UPPER LEVEL RIDGE OVER ALASKA EXTENDS FROM THE SOUTHERN
BERING SEA ACROSS THE SOUTHERN MAINLAND TO THE EASTERN NORTH
GULF COAST THEN SOUTHEASTWARD INTO THE GULF OF ALASKA AND
EASTERN PACIFIC OCEAN. THE RIDGE WILL MOVE EASTWARD...BY 3 AM
TUE THE RIDGE AXIS WILL EXTEND FROM THE EASTERN ARCTIC COAST
TO THE SOUTHERN YUKON TERRITORY AND SOUTHWARD. THE RIDGE WILL
MOVE TO THE YUKON TERRITORY AND SOUTHWARD BY 3 AM WED... WITH
THE TOP OF THE RIDGE BEING FLATTENED OUT AS A SHORT WAVE TROUGH
MOVES EASTWARD.

THE SHORT WAVE TROUGH CURRENTLY EXTENDS FROM THE NECK OF THE
KAMCHATKA PENINSULA TO NEAR ADAK. THE TROUGH WILL MOVE EASTWARD...
BY 3 PM TUE THE TROUGH WILL EXTEND FROM THE NORTHWEST ALASKA
SOUTHWARD TO THE ALASKA PENINSULA. BY 9 AM WED THE TROUGH WILL
FLATTEN OUT OVER THE ALCAN BORDER AS WEAK RIDGING MOVES INTO THE
WESTERN ALASKA INTERIOR.

THE NEXT SHORT WAVE TROUGH IN THE CURRENT SERIES WILL MOVE
ONSHORE ALONG THE WEST COAST BY 9 AM THU...GRADUALLY FLATTENING
OUT IN AMPLITUDE AS IT PROCEEDS EAST TO THE ALCAN BORDER BY 3 PM
FRI...RESULTING IN WESTERLY FLOW ALOFT OVER NORTHERN ALASKA.

THIS WILL BE FOLLOWED BY A MUCH STRONGER SHORT WAVE...NUMBER 3 IN
THE LINEUP...WHICH WILL ARRIVE OVER THE NORTHERN BERING SEA BY 3
AM SAT. SIGNIFICANT COLD ADVECTION WILL DEEPEN THE TROUGH AND
SLOW DOWN THE ITS EASTWARD MOVEMENT...THE TROUGH WILL EXTEND
NORTH- SOUTH ACROSS THE MAINLAND BY 3 AM MON...BRINGING SHARPLY
COLDER TO NORTHERN ALASKA...ESPECIALLY OVER THE WEST COAST AND
WESTERN INTERIOR WHERE 850 MB TEMPERATURES WILL COOL TO BELOW
-20C. THE COLDEST AIR WILL SPREAD EASTWARD TO THE CENTRAL
AND EASTERN INTERIOR BY TUE NIGHT.

THE WEST TO SOUTHWEST FLOW ALOFT OUT AHEAD OF THE THIRD SHORT
WAVE WILL BE FAVORABLE FOR EXPORTING SIGNIFICANT MOISTURE EASTWARD
ACROSS NORTHERN ALASKA...RESULTING IN THE POTENTIAL FOR HEAVY
SNOWFALL. THIS TYPE OF SYNOPTIC PATTERN IS NOT TYPICAL IN
THE MONTH OF MARCH...AT FAIRBANKS THERE HAVE BEEN ONLY 13 DAYS IN
THE MONTH DURING THE PERIOD OF RECORD FROM 1904 TO 2014 WHERE
CALENDAR DAY SNOW AMOUNTS OF 6 INCHES OR MORE HAVE OCCURRED...AN
AVERAGE OF ABOUT ONE SUCH EVENT PER DECADE. THE CURRENT GFS/ECMWF
RUNS AND THEIR ENSEMBLE MEANS AGREE WELL ON THE FORECAST LARGE
SCALE UPPER PATTERN. CURRENT GFS/ECMWF SOLUTIONS INDICATES SNOW
SPREADING TO THE NORTHERN BERING SEA FRI...ARRIVING ON THE WEST
COAST FROM THE SEWARD PENINSULA SOUTH BY FRI EVENING...AND
SPREADING EAST ACROSS THE INTERIOR FRI NIGHT INTO SAT.

AS THE TROUGH INCREASES IN AMPLITUDE...SOUTH TO SOUTHWEST
FLOW ACROSS THE SOUTHEAST INTERIOR COULD BRING OVERRUNNING
SNOWFALL TO THE ALASKA RANGE AND SOUTHEAST INTERIOR DURING
THE UPCOMING WEEKEND.

SURFACE...
A 1003 MB LOW OVER THE GULF OF ANADYR WILL MOVE TO ABOUT 100 MILES
NORTH OF BARROW BY 9 PM TUE...DEEPENING TO 997 MB. THE LOW IS
PROJECTED TO BE ABOUT 250 MILES NORTH OF DEADHORSE BY 3 AM
WED...AND TO ABOUT 300 MILES NORTH OF DEMARCATION POINT BY 3 PM
WED. THESE FORECAST POSITIONS ARE BASED ON A MEAN BETWEEN THE
CURRENT GFS/ECMWF RUNS. AS THE LOW TRACKS ACROSS THE BEAUFORT
SEA...BRISK WEST WINDS WILL DEVELOP ALONG THE WESTERN AND NORTHERN
ARCTIC COAST TUE...SPREADING ACROSS THE CENTRAL AND EASTERN ARCTIC
COASTS TUE NIGHT. NEAR BLIZZARD CONDITIONS COULD DEVELOP ON THE
EASTERN ARCTIC COAST LATE TUE NIGHT. WEST WINDS WILL ALSO SPREAD
ACROSS THE INTERIOR ARCTIC COAST...BUT BE LESS THAN AS THOSE
EXPECTED ALONG THE ARCTIC COAST. A PERIOD OF SNOW IS EXPECTED WITH
PASSAGE OF THE SHORT WAVE TROUGH ALOFT AND A SURFACE WEATHER
FRONT. THE FRONT WILL MOVE ACROSS THE WESTERN ARCTIC COAST
TUE...AND MOVE EAST TO THE ALCAN BORDER BY AROUND MIDNIGHT TUE
NIGHT.

SNOW IS EXPECTED TO BEGIN ON ST LAWRENCE ISLAND BY MID AFTERNOON
MON...SPREADING TO THE WESTERN SEWARD PENINSULA AND NORTHWEST
CAPES BY LATE MON NIGHT. SNOW WILL SPREAD OVER THE REMAINDER OF
THE WEST COAST BY TUE MORNING...INTO THE WESTERN INTERIOR BY TUE
AFTERNOON...AND INTO THE CENTRAL INTERIOR AND NORTHERN PARTS
OF THE EASTERN INTERIOR TUE AFTERNOON INTO TUE EVENING.

AS INDICATED EARLIER IN THE DISCUSSION...THERE IS POTENTIAL
FOR SIGNIFICANT SNOWFALL OVER MUCH OF NORTHERN ALASKA SOUTH
OF THE BROOKS RANGE...BEGINNING ON THE WEST COAST BY FRI EVENING
AND SPREADING EASTWARD OVER THE WEEKEND.

&

.AFG WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FOR PKZ220-PKZ225-PKZ245.

BRISK WIND ADVISORY FOR PKZ200-PKZ210-PKZ215-PKZ225-PKZ230-
PKZ235-PKZ240-PKZ245.
&&

$$

RF MAR 15



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