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000
FXAK69 PAFG 230950
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
150 AM AKDT THU MAY 23 2013

.DISCUSSION...
MODELS ARE MOSTLY SIMILAR THROUGH 48 HOURS. UPPER LEVEL LOW IN
WESTERN CANADA WILL CONTINUE TO TRACK NORTHWARD TO SOUTH OF BANKS
ISLAND BY FRI AFTERNOON. THIS WILL ALLOW THE UPPER LEVEL RIDGE TO
BUILD IN FROM WESTERN CANADA AND EXTEND WESTWARD ACROSS NORTHERN
ALASKA REACHING THE WEST COAST BY SAT EVENING.

THIS BUILDING OF THE RIDGE WILL PUSH MUCH WARMER AIR INTO ALASKA
AND WATCH THE HEIGHTS CONTINUE TO CLIMB. A VERY WEAK UPPER LEVEL
TROUGH WILL MOVE NORTH SAT BUT THE CONVECTIVE PARAMETERS ARE SO
PATHETIC OVER THE CENTRAL INTERIOR THAT AT THIS POINT IT IS
UNLIKELY THAT IT WILL PRODUCE ANYTHING MORE THAN A COUPLE OF STRAY
SHOWERS. HOWEVER...ON SUN AND MON MORE INSTABILITY CREEPS BACK
INTO THE EASTERN INTERIOR WITH THE BUILDING THERMAL TROUGH AND A
WEAK UPPER LEVEL TROUGH DRAPED ACROSS THE CENTRAL INTERIOR RUNNING
NORTHEAST THROUGH SOUTHWEST. THIS COULD PRODUCE A BETTER CHANCE OF
MORE WIDELY SCATTERED SHOWERS.

AN APPROACHING COLD FRONT ALONG THE NORTHWEST ARCTIC COAST WILL
WEAKEN CONSIDERABLE AS IT TRIES TO PUSH EAST BUT WILL GET HUNG UP
OVER THE EASTERN BROOKS RANGE WHICH WILL LIKELY PRODUCE SOME
SHOWERS AT LOWER ELEVATIONS AND SNOWFALL IN THE MOUNTAINS.

THE THERMAL TROUGH WILL EXTEND FROM THE EAST THROUGH THE WEST
BEGINNING SAT EVENING AND THE ISOLATED SHOWERS MAY BE SEEN AS FAR
WEST AS ANVIK ON MON.

GIVEN THE RAPID INCREASE IN TEMPERATURES AND THE EXPECTED
LONGEVITY OF THE NOW ABOVE NORMAL TEMPERATURES...RAPID SNOW MELT
IS GOING TO OCCUR AND THIS COULD CAUSE HYDRO PROBLEMS IN THE
SMALLER STREAMS AND RIVERS. THE RMOPS INDICATE WELL ABOVE NORMAL
TEMPERATURES IN THE UPPER LEVEL RIDGE THAT WILL REMAIN CONSTANT
OVER NORTHERN ALASKA THROUGH 360 HOURS.

FLOODING ALONG THE YUKON RIVER REMAINS THE MAIN TOPIC THOUGH. FORT
YUKON HAS BEEN SPARED THUS FAR BUT UNSURE AS TO WHETHER THE MAIN
JAM UPSTREAM HAS RELEASED...ALTHOUGH IT DOES APPEAR THAT AT LEAST
A PORTION HAS DUE TO OBSERVED ICE FLOW.

AS THE UPPER LOW MOVES NORTH ALONG THE ALCAN BORDER...THIS WILL
ALLOW FOR THE LOWER LEVEL WINDS TO TURN MORE SOUTHWESTERLY OVER
MUCH OF NORTHERN ALASKA AND USHER IN MORE MOISTURE. IT DOES NOT
APPEAR THAT THE RH VALUES WILL DROP BACK DOWN TO THE LOW VALUES
THAT WERE SEEN ON WED DUE TO THE INFLUX OF LOW AND MID LEVEL MOISTURE.

&&

.FIRE WEATHER...THE UPPER LEVEL RIDGE BUILDING IN FROM THE EAST
WILL CONTINUE TO DRY THINGS OUT OVER NORTHERN ALASKA.
HOWEVER...THROUGH AT LEAST THE WEEKEND THUNDERSTORMS DO NOT APPEAR
TO BE A MAJOR CONCERN. THERE DOES APPEAR TO BE AN INCREASING
CHANCE FOR THE FAR EASTERN INTERIOR TO POSSIBLY GET A VERY
ISOLATED THUNDERSTORM ON MON THOUGH NORTH OF CHICKEN TO NEAR EAGLE.


&&

.HYDROLOGY...FLOODING FROM THE YUKON RIVER REMAINS TO BE A THREAT
FOR VILLAGES DOWN RIVER FROM FORT YUKON DUE TO RAPIDLY WARMING
TEMPERATURES. RAPID SNOW MELT THAT WILL NOW OCCUR IS ALSO GOING TO
BE ANOTHER PROBLEM THAT COULD EXACERBATE THE FLOODING.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FOR AKZ220-AKZ221.
&&

$$

CF MAY 13