Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221139

Area Forecast Discussion
National Weather Service Great Falls MT
440 AM MST Wed Feb 22 2017

Updated Aviation Discussion.


Rest of Tonight through Friday Afternoon...
Snow showers will continue to impact the forecast area for the
next couple of days, with variable yet light snow accumulations
across the region depending on smaller scale features that are
difficult to pin down to exact areas. The most significant shower
coverage should be right along a front over the Plains that extends
from near I-15 to US Highway 89 east of Great Falls and points north
and east. This boundary will likely push north and east toward our
northeastern counties today, then become stationary and weaken
overnight tonight. Thus, the best accumulating snow as well as
widespread low ceilings and fog is expected just north and east of
this boundary over north-central MT. Another weak system moves
across SW MT by early this afternoon and will help to produce snow
showers over most mountainous areas. This region will have more low
level instability, so expect the snow showers to be a bit more
intense but also more hit-and-miss than the shower activity
associated with the surface front over the northeast Plains and
along the Canadian border.

Snow shower activity will begin to become more isolated over the
Plains by Thursday and Friday as a broad upper level trough
remains just to the west, with more scattered to possibly
numerous coverage toward higher elevations and across the southern
counties of SW MT with weak lower level northerly upslope flow.

With continued cloud cover across the region, temperatures will
continue to trend cooler but with a relatively smaller diurnal
range with teens and 20s for highs across much of the region, with
colder temperatures in the single digits above zero and teens at
night over the Southwest valleys. Cassell

Sunday night through Friday...Temperatures remain near to above
seasonal averages through mid-week with periods of rain or mountain
snow generally along and west of the Continental Divide. A broad
upper level trough axis crosses Western MT Sunday night, followed by
weak subsidence and minor height rises Monday. This yields fair and
mild weather for Monday and Monday night. Orographic forcing in the
weak westerly flow will maintain chances for snow near to above pass
level over the Northern Rockies. The westerly flow strengthens on
Tuesday, continuing to produce light mountain snow with increasing
downslope winds spreading across N-central MT.  The large scale
pattern begins to change Wednesday night as colder air advects south
through western Canada. While confidence increases with regard to
the colder solution Thursday and Friday, the question of possible
widespread light snow for central Montana remains unresolved as this
outcome would be associated with details in the position and timing
of shortwave energy embedded in the large scale northerly flow. PN


Updated 1140z.

IFR to occasionally MVFR conditions will predominate with -SN and
VCFG over the Plains sites, especially east of I-15, with some
improvement possible by afternoon from I-15 west, though it should
be noted confidence is low. VFR conditions are predominantly
expected over SW MT, but will drop to occasional MVFR or even IFR at
times with -SHSN especially later this afternoon and into the
overnight tonight. Expect mountains to remain obscured by clouds and
snow showers throughout the period. Cassell


GTF  37  21  29  16 /  60  40  40  20
CTB  32  19  25  11 /  60  40  40  20
HLN  39  19  28  13 /  30  30  30  20
BZN  37  15  28  14 /  50  40  50  40
WEY  26   7  23   5 /  50  40  40  40
DLN  33  12  25  10 /  40  40  40  30
HVR  36  27  32  19 /  50  60  50  30
LWT  34  21  29  15 /  80  60  40  30


Winter Weather Advisory until midnight MST tonight Blaine...
Cascade...Chouteau...Eastern Pondera...Eastern Teton...Fergus...
Hill...Judith Basin...Liberty...Meagher...Toole.

Winter Weather Advisory until 6 PM MST this evening Eastern
Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.


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