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Northern Alaska forecast discussion 
National Weather Service Fairbanks Alaska
321 am akdt Friday Sep 4 2015

Discussion...

Upper levels...
at 500 mb...an upper level ridge over the central and western
Mainland of northern Alaska will persist through tonight...then
become partially pinched off by Sunday night as an upper low
advances eastward into the Gulf of Alaska and a low pressure
trough digs southward into the Chukchi Sea.

A weak upper low centered near Bethel will dissipate over
the southwest interior this afternoon.

An upper low centered near 50n/176e...about 250 miles west of
St Matthew island...will move eastward to near Bristol Bay by
Sunday morning and into the northern Gulf of Alaska by Sunday
night.

An low amplitude short wave trough over the far Northwest Arctic
ocean will move southeastward...trough axis Sunday morning will
extending along 180w from 72n to near wrangel island. By Monday
morning the trough will dig southward and increase in
amplitude...trough axis ending from 80n/150w to Wainwright and
southwestward to the Bering Strait. The trough will continue to
dig southwestward through Monday morning...trough axis Monday
morning extending from 78n/140w to deadhorse and southwestward
to Kuskokwim Bay. The digging trough will bring colder air
aloft initially to the Arctic coast...spreading to the
eastern Bering Sea and the Alaska West Coast by Tuesday
morning.

Through Tuesday morning...there are only minor differences
between the operational GFS and European model (ecmwf) runs from the Sep 4/00z
cycle.

Surface...
a 1005 mb low near Bethel will weaken to a barely discernible
1013 mb center over the central Seward Peninsula by Saturday
morning. The associated occluded front...currently extending
from the Yukon Delta to Anchorage and Valdez...will continue to
stretch out eastward and a bit northward...while weakening during
the next 24 hours. A 1027 mb high centered near 76n/128e... about
250 miles northeast of Barter Island...will move eastward into
the Canadian archipelago through Friday night...with a weak ridge
persisting along 75-76n westward across the Beaufort Sea and into
the russian Arctic Ocean. This ridge will weaken and be pushed
southward to just north of the alaskan Arctic coast by Sunday
afternoon as a low pressure trough approaches from the Northwest.

Arctic coast...
over the Arctic coast east of Wainwright...east winds 20-30 miles per hour
with local gusts to around 35 miles per hour will continue today...diminishing
to 10-15 miles per hour by Saturday morning. Winds will be lighter over areas
to the west. Widespread low stratus will persist over areas east
of Wainwright...with areas of fog during the late night and
morning hours. Little or no precipitation is expected through
Sunday. Somewhat colder temperature are expected next week with
snow possible...especially in the Brooks range.

Central and eastern interior...
rain over the Alaska Range and nearby areas today...tapering to
mainly scattered showers by late tonight. Isolated to scattered
showers continuing Saturday. Elsewhere...no precipitation expected
through Sunday.

Western interior...
rain south of Galena south today...tapering to mainly scattered
showers tonight. Isolated to scattered showers over the southern
areas Saturday and Saturday night.

West Coast...
over areas south of Unalakleet...widespread rain or showers
this morning...tapering to scattered showers this afternoon.
Scattered showers over the southern Seward Peninsula southward
tonight through Sunday. Somewhat colder temperatures are expected
from Monday through the rest of the week are the digging trough
brings in colder air from the north.

St Lawrence Island...
isolated to scattered showers expected through Sunday.
Winds...mainly 10 miles per hour or less today through Saturday. North winds
10-20 miles per hour Saturday night and Sunday.

Extended outlook...
operational GFS and European model (ecmwf) runs continue display large differences
in the extended period. The gefs and European model (ecmwf) ensemble means are
more similar...with a cold long wave trough position predominant
over the northern Alaska Mainland. Temperatures will most
likely average below normal over most areas...with an above
normal chance of precipitation.

Coastal hazard potential days 3 and 4...
none expected through Monday. There is potential for a moderate
intensity surface system to move southeastward out of the
Northwest Arctic ocean and affect the northwest Alaska coast with
high surf conditions possible. At this time...forecast confidence
remains low due to large differences between model runs and poor
run to run continuity. Current Canadian global model brings a
moderate strength low center to near Barrow by Tuesday
afternoon...with the GFS position substantially farther to the
southwest..near Point Lay. Gefs ensembles show a large spread of
low center positions at that time...and the low center is totally
smoothed out by the ensemble mean. The European model (ecmwf) run shows no low
center at all. It will be necessary to monitor future model runs
for possible developments in the Arctic.



&&

Hydrology...
no issues. Water levels on the chena river south of the Moose
Creek dam are still slightly elevated...but will continue to fall
slowly.



&&

Afg watches/warnings/advisories...
Small Craft Advisory for pkz235-pkz240-pkz245.

&&

$$

Rf Sep 15

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