Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 212344

Area Forecast Discussion
National Weather Service Great Falls MT
445 PM MST Wed Feb 21 2018

Aviation Section Updated


A somewhat quieter weather pattern will prevail over the next couple
of days across the area, with any chance of snow mainly confined to
Southwest Montana. Over the weekend and into next week, a better
chance of precipitation is possible, although the heaviest amounts
look to be in the mountains. This pattern also favors breezy to
windy conditions in the mountains and over the plains, which will
likely lead to impacts from blowing and drifting snow. Temperatures
will moderate some over the weekend, then decrease again next



Impacts from blowing and drifting snow will be the primary concern
through the weekend, then the focus will turn back towards cold
temperatures and perhaps the return of snowier conditions.

A shortwave diving south through BC at this time will help to
reinforce the upper level trough in place over the Western US. This,
in turn, will keep the cold air locked in place locally through
Friday. The BC shortwave will close off over OR/ID, focusing the
greatest lift/moisture to our south and west. However, there should
be enough moisture for some snow showers/areas of light snow,
primarily along/south of I-90, but with minimal impact.

Over the weekend, zonal flow will lead to increasing winds aloft
over the area. This will combine with a tightening pressure gradient
within a developing lee-side trough and steep lapse rates to produce
a more widespread area of breezy/windy conditions. At this time,
high wind criteria is not expected, although this potential will be
closely monitored. However, what is expected is a more widespread
blowing/drifting snow potential, especially with cold temperatures
and snow appearing to still be loose enough to blow around. At this
point, we will let the current Winter Weather Advisory for blowing
snow cover the ongoing impacts along the Rocky Mtn Front through
this evening. Additional winter weather products for blowing snow
certainly seem likely over the weekend, especially Friday and again
Sunday. It should be noted that blowing snow has led to significant
impacts along the Rocky Mountain Front in recent weeks and
conditions look to go downhill once again in that area. If the snow
is loose enough, ground blizzard conditions are a distinct
possibility along the Rocky Mountain Front where gusts of 40-60 mph
are expected. Elsewhere over the plains, the winds do not look
nearly as strong, but still strong enough to cause impacts to
travel. Those with interests along the Rocky Mountain Front are
encouraged to pay attention to later forecasts and statements
regarding the ongoing/additional blowing snow impacts.

With the windy conditions, a brief moderation in temperatures is
expected, especially by Sunday, but many locations may still not
reach the freezing mark, especially along the Hi-line. Over the
weekend and into next week, a couple of shortwaves will bring
accumulating snow to the mountains. For the plains and valleys, each
shortwave may allow some snow showers to develop, but widespread
accumulating snow at lower elevations doesn`t look likely at this
point. MARTIN


Updated 2345Z.
Overall, VFR conditions will generally prevail over the region
through the period. The exception will be the small chance for some
patchy fog to develop over portions of North Central MT after 06z.
Otherwise, just expect some passing clouds and breezy conditions at
times. Brusda


GTF  -8  13  -7  22 /   0   0  10   0
CTB  -9  14  -8  21 /   0   0  10   0
HLN  -3  18  -2  23 /   0  10  20  10
BZN  -3  20  -2  21 /  10  10  20  10
WEY -10  19  -9  19 /  70  20  20  20
DLN  -3  16  -2  19 /  20  10  30  10
HVR -17   7 -12  15 /   0   0  10   0
LWT  -5  16  -7  23 /   0   0  10  10


Winter Weather Advisory until 8 PM MST this evening Northern
Rocky Mountain Front.


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