Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 182352
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
352 PM AKDT SAT APR 18 2015

.DISCUSSION...

MODELS SOLUTIONS ARE IN REASONABLE AGREEMENT THROUGH 00Z TUESDAY
BEFORE DIFFERENCES IN THE ECWMF AND GFS BECOME APPARENT. THERE ARE
MINOR DIFFERENCES AMONGST THE NAM/GFS/ECWMF REGARDING THE
POSITION AND STRENGTH OF THE CONGLOMERATION OF LOW CENTERS OVER
WESTERN ALASKA.

ALOFT...BROAD LONG WAVE TROUGH REMAINS OVER WESTERN ALASKA/BERING
STRAIT/BERING SEA WITH THE MAIN LOW...AT 504 DAM...CONTINUING ITS
TREK ALONG THE ALASKA PENINSULA. A SECOND BUT WEAKER UPPER LOW...A
512 DAM...IS OVER THE ANDYR GULF EARLY THIS AFTERNOON. A RIDGE
REMAINS STRETCHED FROM THE NORTHWEST OF THE LOWER 48...TO OVER
EASTERN ALASKA AND NORTH OVER THE NORTHERN ARCTIC COAST. THE 504
DAM LOW 170 NM SOUTHEAST OF UNALASKA WILL ROTATE NORTH AND MERGE
WITH THE 512 DAM LOW WEST OF NUNIVAK ISLAND SUNDAY
AFTERNOON...FORMING A NEW UPPER LOW CENTER. OUT AHEAD OF THIS NEW
LOW CENTER...A SHORTWAVE WILL MOVE NORTHWEST SUNDAY AFTERNOON AND
OVER THE SEWARD PENINSULA. AS THIS HAPPENS...THE RIDGE WILL BE
PUSHED WEST WITH THE RIDGE AXIS OVER WESTERN CANADA...NORTHWEST TO
THE EASTERN BEAUFORT SEA COAST. SOUTHERLY FLOW WILL DEVELOP OVER
THE ALASKA RANGE...WITH SEVERAL JET STREAKS RIDING THE FLOW NORTH
AND OVER THE ALASKA RANGE. BY MID WEEK...THE LONG WAVE TROUGH WILL
BE THE PREDOMINANT FEATURE OVER MAINLAND ALASKA...PUSHING THE
RIDGE FURTHER EAST.

SURFACE...A 976 MB LOW 175 NM SOUTH OF UNALASKA WILL CONTINUE TO
MOVE NORTHEAST...WEAKEN AND BE OVER THE YUKON DELTA AS A 984 MB
LOW SUNDAY AFTERNOON. AN INVERTED TROUGH EXTENDING NORTH AND ALONG
THE WEST COAST WILL SHIFT WEST INTO THE BERING SEA...STRENGTHENING
INTO A 983 LOW OVER ST LAWRENCE ISLAND SUNDAY MORNING.
A THIRD LOW CENTER...AT 987 MB...WILL FORM OVER THE UPPER
KUSKOKWIM VALLEY SUNDAY MORNING AND SHIFT NORTH TO THE SEWARD
PENINSULA EARLY SUNDAY EVENING. THIS CONGLOMERATION OF LOW CENTERS
WILL ROTATE NORTH AND STRETCH FROM THE CHUKCHI SEA TO ST LAWRENCE
ISLAND EARLY MONDAY AFTERNOON. MEANWHILE...HIGH PRESSURE EXTENDING
FROM CHUKOTSK PENINSULA TO THE ARCTIC COAST WILL BE PUSHED NORTH
INTO THE HIGH ARCTIC.

EASTERN AND CENTRAL INTERIOR...THE MAIN FORECAST CONCERN WILL BE
THE WINDS AND CONSEQUENTLY ANY FIRE WEATHER CONCERNS FOR THE
ALASKA RANGE. FOR FIRE WEATHER DETAILS...LOOK BELOW TO THE FIRE
WEATHER SECTION. AS THE SOUTHERLY FLOW PERSISTS THROUGH
MONDAY...SEVERAL JET STREAKS WILL RIDE THE WESTERN EXTENT OF THE
UPPER RIDGE TO PROVIDE ENHANCEMENT TO THE ONGOING MODERATE CHINOOK
FLOW ACROSS THE ALASKA RANGE. MODELS CONTINUE TO KEEP 50 TO 60 KTS
OF FLOW AT H700 AND H850 ACROSS THE ALASKA RANGE THROUGH SUNDAY
NIGHT...AND WEAKENING THEREAFTER. WILL KEEP THE HIGH END WIND
ADVISORY FOR ZONES 225...226...227 AND 223 AS IS.
ADDITIONALLY...GUSTY WINDS HAVE DEVELOPED OVER MOST REST OF THE
INTERIOR...BUT NOT EXPECTING ADVISORY LEVELS TO BE MET...EVEN
THOUGH THE SOUTHEAST PORTION OF ZONE 222 FLIRTED WITH 35 MPH
EARLIER THIS MORNING.

BESIDES THE ALASKA RANGE WINDS...THE CHINOOK FLOW WILL CONTINUE TO
PUMP WARMER AIR OVER THE INTERIOR THROUGH LATE SUNDAY. THE WARMEST
DAY WILL BE SUNDAY...WHERE TEMPERATURES WILL CLIMB INTO THE 50S
FOR MOST LOCATIONS...AND EVEN MAY REACH 60 DEGREES IN ZONES 222
AND 223. REGARDLESS...TEMPERATURES WILL BE WELL ABOVE NORMAL ON
SUNDAY.

WESTERN ALASKA...ON GOING BLIZZARD WARNING FOR 213 WILL REMAIN AS
IS. SURFACE OBSERVATIONS FROM AROUND 23Z SHOW THAT VISIBILITIES
AND WINDS ARE MEETING CRITERIA ALONG THE BERING COAST
STRAIT...HOWEVER ST LAWRENCE ISLAND HAS YET TO JOIN IN BUT THE
EXPECTATION IS TO SEE VISIBILITIES LOWERING AS SNOW AND WINDS RAMP
UP THIS EVENING. CONCERNING ZONE 214...DECIDED TO LET THE WINTER
ADVISORY EXPIRE EARLIER SINCE WINDS AND VISIBILITIES WERE NO
LONGER MEETING THE CRITERIA. EXPECTING THE IMPROVING TREND TO
CONTINUE INTO THIS EVENING. ELSEWHERE...A WET AND SLOPPY MESS IS
EXPECTED THROUGH MONDAY MORNING. SNOW/SNOW SHOWERS MIXING WITH
RAIN DURING THE DAYTIME SOUTH OF THE SEWARD PENINSULA. WITH THE
UPPER LEVEL SHORTWAVE MOVING OVER THE SEWARD PENINSULA SUNDAY
AFTERNOON...PERIODS OF SNOW WILL DEVELOP AND CONTINUE THROUGH
MONDAY MORNING. DESPITE WARMING TEMPERATURES ALOFT...EXPECTING
THAT THE PRECIPITATION WILL BE ALL SNOW...WITH LOW SNOW RATIO
VALUES. 24 HOUR SNOWFALL ACCUMULATIONS WILL FALL BELOW WARNING
THRESHOLDS...WITH 3 TO 6 INCHES OF SNOW FORECAST FOR ZONES
207...208...209 AND 210.

NORTH SLOPE...WINDS WILL INCREASE ON THE NORTH SLOPE TONIGHT AS
THE GRADIENT BETWEEN THE ARCTIC HIGH AND THE DEVELOPING LOW OVER
ST LAWRENCE ISLAND TIGHTENS. AS WIND INCREASES...AREAS OF BLOWING
SNOW WILL DEVELOP. DESPITE EAST WINDS OF 25 TO 35 MPH...NOT
EXPECTING ANY PROBLEMS WITH VISIBILITY REDUCTIONS TO BELOW ONE
MILE AT THIS TIME.

REGARDING TEMPERATURES ON THE NORTH SLOPE...H850 TEMPERATURES
WARM WILL RAPIDLY WARM FROM NOW THROUGH SUNDAY EVENING AND RANGE
FROM +4C TO +6C OVER THE EASTERN NORTH SLOPE. AT THE
SURFACE...THIS POTENTIALLY COULD TRANSLATE TO TEMPERATURES IN THE
30S AND LOWER 40S. WITH ONGOING ISSUES ALONG THE DALTON HIGHWAY
NORTH OF THE BROOKS RANGE...THESE WARM TEMPERATURES COULD CAUSE
ADDITIONAL PROBLEMS AS SNOW AND ICE MELTS WITH WARMING
TEMPERATURES.


&&

.FIRE WEATHER...

WARM AND DRY CONDITIONS ARE EXPECTED OVER THE CENTRAL AND EASTERN
INTERIOR...ESPECIALLY IN THE CHINOOK ZONES ALONG THE NORTH SLOPES
OF THE ALASKA RANGE. MIN RH VALUES THIS AFTERNOON LIKELY TO DIP
INTO THE 20S COMBINED WITH ADVISORY LEVEL WINDS IN AND NEAR THE
ALASKA RANG PASSES WILL COMBINE FOR METEOROLOGICAL RED FLAG
CONDITIONS HOWEVER NO HEADLINES AT THIS TIME AS FUELS IN SNOW FREE
AREAS NOT DRY ENOUGH.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ223-AKZ225-AKZ226-AKZ227.

BLIZZARD WARNING FOR AKZ213.

GALE WARNING FOR PKZ210-PKZ220-PKZ225-PKZ230-PKZ235-PKZ240-
PKZ245.

BRISK WIND ADVISORY FOR PKZ200-PKZ215-PKZ220-PKZ230-PKZ235-
PKZ240-PKZ245.
&&

$$

LTH APR 15



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