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Northern Alaska forecast discussion 
National Weather Service Fairbanks Alaska
136 PM akdt Tuesday Sep 1 2015

Discussion...the models are in decent agreement out though Friday
morning.

Upper air...
a trough aloft over the western Beaufort Sea will
extend from 200 miles north of Barrow to inuvik and southeastward
by late tonight. The trough will then merge with a short wave
trough incoming from the west. This next short wave trough extends
from 200 miles north of wrangel island southwestward to the
russian Arctic coast...and will move eastward to extend from
80n/130w to Demarcation Point by late Wednesday night. The
operational models are in good agreement about the placement of
the shortwave.

The models are in good agreement that an upper level ridge
that currently extends from the chukotsk peninsula to the eastern
Aleutians will build east over Mainland Alaska overnight tonight.
The ridge will remain in place over Mainland Alaska through early
Friday.

Thursday evening the models split off an upper level low from the
eastern moving shortwave. There are some model differences with
how the models handle this situation. The European model (ecmwf) has the low centered
over the MacKenzie river Delta by Friday morning. The NAM and the
GFS have the low centered roughly over Old Crow Friday morning.
The European model (ecmwf) is the deepest of the three solutions. We prefer the GFS
solution.

Off to the west a low amplitude short wave trough moving up the
west side of the ridge is now over the western Aleutians and will
move northeastward to St Lawrence Island and Norton Sound by
Wednesday afternoon...then dampening out some as it moves to the
chukotsk peninsula and the Chukchi Sea by Thursday morning. The
models are have come into better agreement about the general
placement and movement of this feature.

Surface...
a 1025 mb high over western Alaska will continue to move to the
east this evening. A broad area of high pressure will sit over
Mainland Alaska on Wednesday.

An occluded front over the eastern Beaufort Sea will weaken and
move east tonight.

A 1004 mb low centered about 100 miles southwest of the pribilofs
will weaken and move to near or just west of St Lawrence Island by
Wednesday afternoon. The operational GFS agrees well with the
European model (ecmwf)..putting the center about 100 miles west of St Lawrence
Island by Wednesday evening. The NAM position is slightly farther
to the east. We prefer the GFS solution.

An occluded front stretching southeast from this low will move to
Gambell to St Marys by 4pm Wednesday...to provideniya to Anvik by 4am
Thursday...to the Bering Strait to a frontal wave near Nome to McGrath
by 4pm Thursday...to a 1004 mb frontal wave in the Bering Strait to
McGrath by 4am Friday and then weakening in place.



Surface weather...

Arctic coast... the pressure gradient over the eastern Arctic
coast will continue to weaken this evening. Gale fore west winds
winds across zone 204 north Arctic coast will decrease late his
afternoon and this evening. Elsewhere along the Arctic
coast...winds expected to be 15 miles per hour or less through Wednesday
morning. East winds 15-20 miles per hour developing over all of the Wednesday
night. East winds 25-30 miles per hour expected along the central and eastern
Arctic coast Thursday morning.

Central and eastern interior...
a few showers in the southeaster interior this evening.
Otherwise...no precipitation is expected through Thursday.
Decreasing clouds most areas tonight with the incoming high
pressure ridge. Clear or partly skies Wednesday and Wednesday
night...widespread frost tonight with low temperatures tonight in
the middle 20s to lower 30s.

Western interior...
no precipitation expected through Wednesday. Rain
likely in the lower Yukon valley Wednesday night and
Thursday. Chance of rain Wednesday night and Thursday over
parts of the lower Koyukuk and middle Yukon valleys. Low
temperatures tonight in the upper 20s to middle 30s under mostly
clear skies.

West Coast...
no precipitation expected through this evening. Rain developing
in the Yukon Delta Wednesday morning out ahead of a northeastward
moving surface front...spreading to eastern Norton Sound and the
Nulato Hills by Wednesday evening. Rain likely on the southern
Seward Peninsula coast Wednesday night and Thursday spreading to
Kotzebue Sound by Friday.

St Lawrence Island...
rain Wednesday and Wednesday night as the surface low and front
move northeast. East winds 25-35 miles per hour out ahead of the front
tonight and Wednesday...becoming south and decreasing early
Wednesday evening after the frontal passage.

Coastal hazard potential days 3 and 4...moderate surf possible
Thursday and Thursday night along Arctic coast east of Barrow with
east winds around 30 miles per hour.

Fire weather...
warmer and drier conditions are expected across the interior as
high pressure builds over the area.

Hydrology... river levels on the chena river
remain elevated but are gradually falling. Elsewhere...no
hydrologic issues.
&&

Afg watches/warnings/advisories...
Small Craft Advisory for pkz210-pkz245.

Gale Warning for pkz210.

&&

$$

Sep 15

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