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000
FXAK69 PAFG 161131
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
331 AM AKDT THU MAY 16 2013

.DISCUSSION...
AN EXPANSIVE UPPER LOW CENTER WITH A VERY COLD AIR MASS EXTENDS
FROM THE NORTHERN BERING SEA NORTHWARD INTO THE ARCTIC OCEAN. TWO
DISTINCT LOW CENTERS ARE LOCATED ABOUT 150 MILES NORTHEAST OF
WRANGEL ISLAND AND OVER THE EASTERN CHUKOTSK PENINSULA. THROUGH
FRIDAY NIGHT...THE TROUGH WILL GRADUALLY BECOME REORIENTED
SOUTHEAST TO NORTHWEST...BY SATURDAY THE TROUGH WILL EXTEND FROM
PRINCE WILLIAM SOUND TO THE NORTHWEST ALASKA COAST AND
NORTHWESTWARD INTO THE ARCTIC OCEAN. OUT AHEAD OF THE TROUGH...
SOUTHERLY FLOW ALOFT OVER THE EASTERN INTERIOR WILL CONTINUE
THROUGH TONIGHT...THEN WEAKEN SATURDAY AS THE SOUTHERN PART
OF THE TROUGH PUSHES EASTWARD.

AT THE SURFACE...A 991 MB LOW CENTERED OVER OUTER KOTZEBUE
SOUND WILL MOVE TO NEAR CAPE LISBURNE BY LATE THIS AFTERNOON
AND TO 250 MILES NORTH OF CAPE LISBURNE BY LATE FRIDAY
AFTERNOON...FILLING TO AROUND 995 MB. A COLD FRONT WILL MOVE
EASTWARD ACROSS THE NORTHERN ALASKA THROUGH SATURDAY
AFTERNOON...BRINGING A SHARPLY COLDER AIR MASS. 850 MB
TEMPERATURES IN THE CORE OF THE TROUGH WILL BE AS COLD AS -18
TO -20 DEGREES CELSIUS TODAY...AND AS COLD AS -14 TO -16 DEGREES
CELSIUS SATURDAY. AT FAIRBANKS...AN 850 MB TEMPERATURE OF
-14 DEGREES CELSIUS WOULD BE THE COLDEST EVER OBSERVED THIS
LATE IN THE SEASON. SATURDAY WILL BE THE COLDEST DAY...WITH
HIGH TEMPERATURES IN THE INTERIOR MOSTLY IN THE 30S. SNOW
OR MIXED RAIN AND SNOW WILL SPREAD EASTWARD ACROSS THE
FORECAST AREA AS THE FRONT AND UPPER TROUGH MOVE EASTWARD.

PERIODS OF RAIN AND SNOW OVER MUCH OF THE WEST COAST TODAY...
WITH SCATTERED RAIN AND SNOW SHOWERS OVER THE WESTERN INTERIOR.
SCATTERED RAIN AND SNOW SHOWERS...OR PERIODS OF RAIN AND
SNOW...SPREADING EASTWARD ACROSS THE CENTRAL AND EASTERN
INTERIOR TONIGHT AND FRIDAY.

A BUILDING UPPER RIDGE WILL MOVE EASTWARD TO THE ALASKA
COAST BY SUNDAY AFTERNOON AND TO THE EASTERN INTERIOR BY
TUESDAY AFTERNOON. THIS WILL ALLOW TEMPERATURES TO REBOUND
TO NEAR SEASONAL NORMALS. THE ECMWF ENSEMBLE MEAN SUGGESTS
THE RIDGE MAY BREAK DOWN INTO A SOUTHWEST FLOW NEXT
WEDNESDAY...WHILE THE GFS ENSEMBLE MEAN HOLDS THE RIDGING
OVER THE CENTRAL AND EASTERN INTERIOR.

&&

.FIRE WEATHER...
BRISK SOUTHERLY GAP WINDS NEAR ALASKA RANGE PASSES WILL
DIMINISH LATE TONIGHT. NO FIRE WEATHER ISSUES AS FUEL
CONDITIONS REMAIN GREEN.

&&

.HYDROLOGY...
FLOOD ADVISORY REMAINS IN EFFECT FOR THE TANANA RIVER NEAR
SALCHA. AN ICE JAM FORMED ON THE TANANA RIVER DOWNSTREAM
FROM THE BOONDOX BAR IN SALCHA WEDNESDAY AFTERNOON.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
FLOOD ADVISORY FOR AKZ222-AKZ223.
HEAVY FREEZING SPRAY WARNING FOR PKZ200.
GALE WARNING FOR PKZ220.
BRISK WIND ADVISORY FOR PKZ200-PKZ210-PKZ225.

&&

$$

RF MAY 13