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Northern Alaska forecast discussion 
National Weather Service Fairbanks Alaska
247 am akst Monday Dec 22 2014


Quiet weather pattern is expected to continue over northern
Alaska through Friday. Somewhat colder temperatures can be
expected over the Arctic coast and most of the interior for
most of this week...with a warming trend beginning over the

Upper air...
current GFS/NAM operational runs are similar through Wednesday
night. A cold upper level trough extends from a weak low near the
new siberian islands southeastward along the northern Siberia
coast to the Bering Strait and Norton Sound. This trough and its
colder air mass will move slowly eastward across the northern two
thirds of northern Alaska through Wednesday night. The European model (ecmwf) run differs
from the NAM/GFS...depicting a smoother and lower amplitude long
wave trough with the coldest air remaining north of the Arctic
coast. A weak short wave moving out of the long wave pattern is
carried eastward across northern Alaska from the Brooks northward
with timing similar to the movement of the main trough on the
GFS/NAM runs. The operational GFS solution is well supported by
its ensemble mean. We prefer the NAM/GFS consensus on the
handling of this upper trough.

After the upper trough exits to the northeast...a weak upper flow
pattern will be maintained over northern Alaska through Friday. This
will be followed by the development of a high amplitude upper
ridge which will push northward into eastern Alaska over the
weekend. There are minor differences between the GFS/European model (ecmwf)
operational runs but good agreement between the gefs/naefs and
European model (ecmwf) ensemble means. Strong southerly flow on the back side of
the ridge will bring warmer temperatures to northern
Alaska...especially south of the Brooks range where the ensemble
means are indicating 850 mb temperatures as warm as -4c. Behind
the upper low will into the southern Bering Sea.
Positions from of the operational runs prefer the
ensemble means which have a mean center near 55n/175-180w Sat

winds over the northwest convective available potential energy and the Bering Strait have
diminished since yesterday with the pressure gradient loosening
noticeably since Friday evening. Extensive stratus covers the
northern Bering Sea...much of the West Coast and western/central
interior and Arctic coast. There are areas of stratus over parts
of the eastern and northeast interior. While a colder airmass is
expected over the northern two thirds of northern Alaska for the
next few days...surface temperatures will be cloud cover
dependent...with mitigation of the air mass radiative temperatures
in areas of stratus. A generally light wind flow pattern will
continue over the Mainland through Wednesday.

Scattered snow showers today over the West Coast from the
northern Seward Peninsula northward...northwestern interior...and
western parts of the Arctic slope/Brooks range. Scattered snow
showers will spread eastward across the remainder of northern
Alaska through Tuesday as the upper level trough moves east.

Noticeably warmer temperatures are expected over most of northern
Alaska by sun as the strong upper ridge builds in. Chinook winds
will likely develop in Alaska Range passes Sat. Easterly gales
are expected to develop over the northern Bering Sea including St
Lawrence Island Sat afternoon or evening as a moderately strong
storm moves northward into the Bering Sea. By Sat evening...gefs
ensemble mean placing a mean 962 mb center about 150 miles
southwest of St Matthew island. Consensus of the current GFS/European model (ecmwf)
operational runs puts the low center about 50-100 miles east of
this position Sat evening. Precipitation associated with this
system expected to spread northward to the southwest interior and
southern West Coast Sat afternoon. Temperatures could be warm
enough for mixed precipitation in areas of the West Coast south of
Norton Sound as indicated by GFS model soundings.

Coastal hazard potential days 3 and 4...none.


Afg watches/warnings/advisories...

Heavy freezing spray warning...pkz210.


Rf Dec 14

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