000
FXAK69 PAFG 171413
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
613 AM AKDT FRI MAY 17 2013

.DISCUSSION...
AN UPPER TROUGH WITH UNSEASONABLY VERY COLD AIR ALOFT EXTENDS
FROM BRISTOL BAY NORTHWARD INTO THE ARCTIC OCEAN...WITH AN
UPPER LOW CENTER NEAR CAPE LISBURNE. THE TROUGH WILL GRADUALLY
BECOME ORIENTED SOUTHEAST TO NORTHWEST...BY EARLY SUNDAY MORNING
THE TROUGH AXIS WILL EXTEND FROM THE NORTHWESTERN PANHANDLE TO
NORTH AND WEST OF WRANGEL ISLAND. THIS WILL ALLOW THE VERY COLD
AIR MASS TO SPREAD EASTWARD ACROSS THE REMAINDER OF NORTHERN
ALASKA. THE UNSEASONABLY VERY COLD AIR MASS WILL MODIFY A
LITTLE BUT STILL BE EXTREMELY COLD FOR THIS LATE IN THE SEASON.
850 MB TEMPERATURES OVER THE WESTERN INTERIOR COULD BE AS COLD
AS -18 DEGREES CELSIUS TONIGHT. THE 850 MB TEMPERATURE AT
FAIRBANKS COULD FALL TO AROUND -14 DEGREES CELSIUS SATURDAY
THROUGH SUNDAY. THIS TEMPERATURE...IF IT OCCURS...WOULD BE
THE COLDEST EVER OBSERVED AT 850 MB THIS LATE IN THE SEASON.

PRECIPITATION WILL SPREAD EASTWARD ACROSS NORTHERN ALASKA
AS THE UPPER TROUGH AND ITS VERY COLD AIRMASS SWING EASTWARD.
HEAVY SNOW AMOUNTS ARE EXPECTED IN ZONE 218...AT ELEVATIONS
ABOVE 1500 FEET IN ZONES 220-221-222-223...AND IN ZONES
224-225-226. AS THE ADVANCING TROUGH PROVIDES PLENTY OF
LIFT IN A MOIST AIRMASS. IN ZONES 220-221-222-223...THE
PRECIPITATION MAY BEGIN AS RAIN OR MIXED RAIN AND SNOW...BUT
WILL LIKELY BECOME ALL SNOW TONIGHT AS THE SHARPLY COLDER
AIR SPREADS EASTWARD.

GFS/ECMWF OPERATIONAL RUNS AND ENSEMBLE MEANS INDICATING
A RETURN TO NEAR NORMAL TEMPERATURES BY TUESDAY AS A
STRONG UPPER RIDGE BUILDS NORTHWARD ACROSS THE ALASKA
MAINLAND.

&&

.FIRE WEATHER...
NONE.

&&

.HYDROLOGY...
MINOR FLOODING IS OCCURRING ON THE YUKON RIVER AT EAGLE. ICE
BEGAN MOVING AROUND 1230 AM THEN BECAME STOPPED UP IN FRONT OF THE
VILLAGE AROUND 3 AM. AN ICE JAM HAS PROBABLY FORMED DOWNRIVER FROM
EAGLE. FLOOD WARNING HAS BEEN ISSUED FOR THE YUKON RIVER AT EAGLE.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FOR AKZ218-AKZ225-AKZ226.

WINTER WEATHER ADVISORY FOR AKZ220-AKZ221-AKZ222-AKZ223-AKZ224.

BRISK WIND ADVISORY FOR PKZ200-PKZ225-PKZ230.

FLOOD WARNING FOR THE YUKON RIVER AT EAGLE.
&&

$$

RF MAY 13