Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221048
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
348 AM MST Sun Jan 22 2017

.DISCUSSION...

Today through Tuesday...Large upper level disturbance to bring
periods of light snow...and perhaps some freezing drizzle at
times...during the short term forecast. This morning we still find
ourselves in between weather systems with a large upper low to
our northeast in Canada...a sharp upper low off the coast of
OR...and a ridge of high pressure to our south. Each feature will
have some sort of affect on our weather this morning through the
daytime hours. The upper low in Canada is sending low level clouds
to northern MT. This will not only cause aviation concerns...but
may bring areas of flurries or light freezing drizzle through
today. The best chances for this will come from Cut Bank to Havre.
Meanwhile the sharp low to our west will send a weak wave of
energy and moisture up over the ridge this morning. So far nothing
more than low to mid level clouds have been the result...although
can`t rule out flurries or a brief light snow shower...especially
across the south. By late this afternoon and through the evening
hours...high pressure ridge breaks down and more moisture filters
into the region. Snow may begin across the south...then spread
across much of the CWA tonight into Monday morning...as a broad
upper low forms over the area. This newly formed low then tracks
to our south during the day Monday...bringing more widespread snow
to our region. NAM and GFS are hinting that a push of mid level
dry air will be possible for Monday. With abundant lower level
moisture...this mid level dry punch could result in areas of
freezing drizzle at times. Placed mention in the forecast for this
threat...mainly in central and southern portions. As the low
exits our region Monday night into Tuesday...cold Canadian air
gets drawn down in our CWA...and perhaps lingering more light snow
to the region. Lingering moisture caught up in northwest flow
will then provide scattered snow showers for Tuesday. Decided to
hold off on any winter weather highlights at this point. There
still remains uncertainty on where the impactful snow sets up.
Right now 2 to 4 inches are possible across the north...with 1 to
2 in the central...and 2 to 6 in the south. Some models are
however hinting a more southerly track is possible with the
mentioned upper low. This would limit the impacts to the
south...while bringing light snow to the north. Hopefully this
morning`s model runs can help raise confidence in the storms
track. Winds may be a bit gusty...especially across the south
today...then return to normal breezes throughout the short term.
Slightly cooler...but near normal...temperatures are expected for
today with the enhances cloud cover. As cold air filters in from
the north on Monday and Tuesday...a cooling trend will continue.
Highs in the 20s with lows in the teens and single digits can be
expected. Anglin

Tuesday night through Sunday...Northerly flow aloft will persist
across the region through late this week with weak embedded
shortwave energy bringing a slight chance for snow showers Tuesday
night through Wednesday. Temperatures begin on the cool side,
slightly below seasonal averages, but gradually warm late this week
into next weekend as an upper level ridge amplifying along the west
coast gradually shifts inland. Warming aloft will initially be
realized across the plains of N-central MT first as a lee-side
surface trough of low pressure brings breezy W/SW winds late this
week into the weekend. Surface high pressure situated over the
interior western US late this week will lead to temperature
inversions in SW MT valleys where warming will be subdued with some
air quality impacts also possible. By late next weekend, models
indicate the upper ridge will flatten as energy moves into western
Canada, resulting in strengthening winds and continued mild
temperatures across N-central MT. Hoenisch

&&

.AVIATION...
Updated 0539Z.

Very slow-moving cold front extending west-southwestward over
southern SK and AB looks to drift south-southeastward into far-
northern North-Central Montana next 24-hours. This will allow MVFR
or lower CIGS to develop at KCTB/KHVR. In addition, periods of
freezing drizzle, perhaps mixed with light snow, and patchy freezing
fog are possible at and near KHVR after 07Z/Sun. Otherwise,
unsettled southwesterly flow aloft will persist and a pronounced
disturbance within this flow will reach Southwest Montana between
00Z and 06Z/Mon. This disturbance will cause CIGS to lower to MVFR,
possibly worse, over Southwest and much of Central Montana toward
and especially after 00Z/Mon. Periods of light snow and mountain
obscuration are possible throughout the period along the Continental
Divide and higher terrain of Southwest Montana. In addition, light
snow and/or freezing drizzle may occur at lower elevations of
Southwest and Central Montana toward and especially after 00Z/Mon.
Jaszka

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  30  11  27  12 /  10  40  40  40
CTB  26  12  25  10 /  20  50  50  30
HLN  27   9  22   7 /  20  40  20  30
BZN  30  14  25   8 /  20  20  40  50
WEY  24  14  24   2 /  50  70  60  60
DLN  29  14  29   8 /  30  30  40  50
HVR  29  15  28  13 /  10  40  50  30
LWT  32  15  25  13 /  10  20  40  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls


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