Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 172200
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
100 PM AKST WED DEC 17 2014

.DISCUSSION...

DETERMINISTIC GUIDANCE ARE GENERALLY IN GOOD AGREEMENT THROUGH
THE FIRST 60 HOURS...WITH DIFFERENCES BECOMING MORE APPARENT
THEREAFTER. SPECIFICALLY...DIFFERENCES IN HOW THE 500 HPA RIDGE
EVOLVES THAT NOSES INTO NORTHERN AK...YUKON...AND NORTHWEST
TERRITORIES AND THE HANDLING OF THE BROAD LOW PRESSURE AREA OVER
THE BERING AND SOUTHWEST AK BEGINNING LATE FRI AND SAT. GUIDANCE
OTHERWISE IS STILL ON COURSE FOR MUCH OF THE SHORT-TERM AND
MEDIUM RANGE UP TO FRI...OUTSIDE OF MESOSCALE DETAILS AND LOCAL
EFFECTS. AS SUCH...THE SPIRIT OF THE GOING FORECAST OVERALL IS OK
AND NO DRASTIC CHANGES ARE ANTICIPATED.

WV SATELLITE SHOWS A WELL DEFINED LOW IN THE CENTRAL BERING WITH
ANOTHER LOW IN THE NORTHERN PACIFIC SOUTH OF THE ALEUTIAN ISLANDS
AND THE AK PENINSULA. THE LATTER...IS A STRONG CYCLONE THAT WILL
BE INFLUENCING AREAS MORE SO OUTSIDE OF OUR AREA OF
RESPONSIBILITY. A SHORT-WAVE TROUGH IS CURRENTLY MOVING NORTH OVER
THE LOWER YUKON VALLEY THATS APPARENT FROM WV AS WELL. NASA SPORT
NIGHTTIME MICROPHYSICS SHOWS MID-LEVEL STRATUS WITH BASES AROUND
6-9 KFT OVER MOST OF THE NORTH SLOPE COAST. A MIX OF STRATUS AND
HIGH- LEVEL CLOUDS ARE ELSEWHERE IN NORTHERN AK

THE SFC LOW ASSOCIATED WITH THE LOW OVER THE BERING HAS A CENTRAL
PRESSURE OF AROUND 983 HPA AT 9 AM...WHILE THE CYCLONE IN THE
NORTHERN PACIFIC HAS A PRESSURE OF ABOUT 967 HPA. SFC OBS SHOW
FLURRIES OVER PORTIONS OF THE NORTH SLOPE. LIGHT SNOW IS SEEN OVER
THE UPPER KOYUKUK VALLEY AND IN THE SEWARD PENINSULA NORTH TO THE
WESTERN BROOKS RANGE. THIS WEATHER IS ASSOCIATED WITH THE
APPROACHING S/W TROUGH AND TOPOGRAPHIC LIFT. OTHERWISE...THE REST
OF THE ACTIVE WEATHER IS SOUTH OF THE AK RANGE IN TERMS OF
PRECIPITATION.

.ALOFT...

LONG WAVE TROUGH FIRMLY IN PLACE ALOFT OVER THE BERING SEA AND
THE WESTERN HALF OF AK WITH A RIDGE BUILDING ON THE WEST
COAST/WESTERN CANADA THU. JET STREAM IS LOCATED IN THE NORTHERN
PACIFIC WITH IT STAYING WELL SOUTH OF NORTHERN AK THROUGH THE
FORECAST PERIOD. THE MID-LEVEL LOW IN THE BERING WILL CONTINUE TO
MOVE WEST AND WEAKEN THEN DISSIPATE BY THU...AS A STRONG MID-
LEVEL LOW MOVES EASTWARD SOUTH OF THE KAMCHATKA PENINSULA. 500
HPA LOW IN THE NORTHERN PACIFIC WILL MOVE INTO THE SOUTHERN HALF
OF THE GULF OF AK THU WHILE WEAKENING...AND THEN BE DRAWN INTO THE
BROAD AREA OF LOW PRESSURE THATS DEVELOPING OVER THE BERING LATE
THU/EARLY FRI. THE BROAD LOW IS GENERALLY CENTERED OVER SOUTHEAST
AK AND THE EASTERN ALEUTIAN ISLANDS BY SAT. OTHERWISE...RIDGE
BUILDS INTO NORTHERN AK AND THE MACKENZIE RIVER BASIN THU AND
STAYS IN PLACE FRI OVER NORTHERN AK.

.SURFACE...

THE SURFACE LOW IN THE BERING WILL CONTINUE TO WEAKEN AND DRIFT
WEST. A WEAK FRONTAL BOUNDARY EXTENDS FROM THE LOW EAST INTO THE
KOTZEBUE SOUND CURRENTLY. THE FRONT WILL CONTINUE TO WEAKEN AND
DISSIPATE TONIGHT. OTHERWISE...THE SFC LOW SOUTH OF THE ALEUTIAN
ISLANDS WILL MOVE EAST INTO THE SOUTHERN HALF OF THE GULF OF AK
WHILE WEAKENING. COMPLEX SURFACE PATTERN DEVELOPS THEREAFTER WITH
A BROAD SFC LOW COMING FROM THE WEST THAT MOVES EAST INTO THE
WESTERN ALEUTIAN ISLANDS THU WITH MULTIPLE LOW PRESSURE CENTERS.
A STRONG SFC LOW PRESSURE SYSTEM THEN DEVELOPS AND ORGANIZES SOUTH
OF THE AK PENINSULA/EASTERN ALEUTIAN ISLANDS FRI WITH GUIDANCE
GENERALLY SUGGESTING TWO MAIN LOW CENTERS FRI/EARLY SAT.

MAIN CONCERN IS WINDS FOR THIS FORECAST PERIOD. PRECIPITATION
IN ON THE QUIET SIDE IN OUR AOR. LOCAL WINDS...TANANA VALLEY
JET...WILL BECOME ACTIVE AS THE PRESSURE GRADIENT INCREASES WITH
HIGH PRESSURE IN THE YUKON AND THE SFC LOW MOVING INTO THE
SOUTHERN HALF OF THE GULF OF AK LATE THU AND FRI. INCREASING GUSTS
AND WINDS IN THE PASSES OF THE AK RANGE ARE ALSO EXPECTED
BEGINNING TOMORROW INTO FRI. WINDS WILL CONTINUE TO BE MODERATE
OVER THE BERING STRAIT AND OVER OUR MARINE AREAS NEAR ST LAWRENCE
ISLAND. WINDS WILL BECOME MORE ELEVATED IN THOSE AREAS FRI INTO
SAT AS THE PRESSURE GRADIENT INCREASES IN MAGNITUDE THAT IS
ASSOCIATED WITH THE DEVELOPING LOW IN THE GULF OF ALASKA FRI-SAT.

TONIGHT AND TOMORROW...ISOLATED TO SCATTERED SNOW SHOWERS OVER THE
NORTH SLOPE...NEAR THE BROOKS RANGE...AND ON THE EXTREME END OF
WEST COAST/OVER THE NORTHEASTERN BERING SEA. DRY CONDITIONS ARE
GENERALLY ANTICIPATED TOMORROW NIGHT INTO FRI NIGHT OVER THE WEST
COAST AND INTERIOR.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE

&&

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

SMALL CRAFT ADVISORY FOR PKZ210.

GALE WARNING FOR PKZ210.

BRISK WIND ADVISORY FOR PKZ225-PKZ230.
&&

$$

ET DEC 14


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