Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 171638
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
938 AM MST Wed Jan 17 2018

.UPDATE...
Updated forecast is out. No significant changes this morning. Did
increase cloud cover sooner, as a chinook arch has developed. Left
temperatures fairly close to the overnight forecast. Winds should
help warm temperatures later today.

Main concern then turns to the snow event Thursday into Friday
morning. There is a chance for rain on the leading edge of the
precipitation, but because most of the precipitation is coming in
at night and the cold air will come in rather quickly, rainfall
will be limited. The snow will begin over the Rockies on Thu and
end early Friday...while another area of snow is expected south
of a Great Falls to Lewistown line from late Thursday evening
into Friday morning. Areas along the Highway 2 corridor from Cut
Bank to Havre are expected to receive little/no snowfall from this
event. Brusda

&&

.SYNOPSIS...
An upper level ridge of high pressure over the region today will
slowly move eastward tonight as a Pacific cold front approaches
the region. Expect light snow to develop by Thursday morning over
the Rocky Mountain Front, with a mix of rain and snow developing
Thursday night over Central and Southwest MT. Afternoon temperatures
will be mild on Thursday, but gradually cool down into the 20s and
30s over the weekend and into early next week.

&&

.AVIATION...
Updated 1645Z.
A chinook arch will reside over the region today and into this
evening. Otherwise, expect light snow to develop towards 12z over
the Rocky Mountain Front. Some passes/mountains could become
obscured after 12z Thu. Some haze/pollution will affect the Helena
valley until mid afternoon today, until the inversion breaks.
Otherwise VFR conditions are expected across the region through
the period. Brusda

&&

.PREV DISCUSSION...
/ISSUED 450 AM MST Wed Jan 17 2018/

Today through Tonight...Areas of mid and high clouds will move
through a shortwave ridge of high pressure, as gusty westerly winds
continue over the plains. Patchy fog and low cloudiness in some
southwest valleys will dissipate throughout the morning, allowing
temperatures there to warm into the 30s for most of these areas.
Over the north central Montana plains, gusty westerly winds have
warmed most of the area into the 20s early this morning.
Temperatures in the Milk River valley of northern Blaine County
should also warm similarly throughout the morning. Highs today over
the plains should warm through the 30s into the 40s. The next
Pacific weather system to impact the area will break down the high
pressure ridge tonight, which will strengthen winds aloft, increase
cloudiness, and bring a chance of rain and snow to the mountains of
the Rocky Mountain Front. Winds will increase further over the
plains of north central Montana, but they will also blow over ridge
tops and favored valleys of southwest Montana. Gusts to 70 mph at
times are likely along the Rocky Mountain Front, as the plains
mostly see gusts to 45 mph. Am not anticipating a need for any High
Wind highlights at this time. The increasing clouds and gusty winds
will keep overnight lows in the 20s in the southwest valleys and in
the 30s elsewhere. Coulston

Thursday Night through Wednesday...A cold front will move southeast
through the forecast area in the wake of the Thursday disturbance,
causing a cooling trend. Highs in the 40s on Thursday will cool
into the 30s on Friday, then into the 20s for the weekend into
early next week. Lows in the 20s and 30s Thursday night will also
cool into at least the single digits and teens above zero by
Monday night. The passage of this front, combined with increasing
moisture ahead of the approaching Pacific low pressure trough will
bring a very good chance for precipitation Thursday night into
Friday, mainly over the Rocky Mountain Front and over southwest
Montana. Mountain snow with mix of rain and snow at lower
elevations will change to all snow behind the front Thursday
night. Significant accumulations appear to be unlikely this time
due to the fast-moving nature of the system, but the rapid change
in temperature and precipitation type may cause some icy roads,
possibly warranting winter weather highlights. The Pacific trough
will move over the western United States Friday into Saturday,
bringing the aforementioned colder air into the area, along with a
chance of light snow. Weaker disturbances in the westerly flow
aloft will keep the chance for snow mainly in the mountains Sunday
into Monday, but a stronger shortwave trough will bring a better
chance for snow on Tuesday, mainly along the Continental Divide
and over the southwest MT mountains. CC/Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  43  39  47  29 /   0  10  10  60
CTB  40  35  43  29 /   0  10  20  20
HLN  34  23  39  20 /   0   0  30 100
BZN  34  22  42  27 /   0  10  10  90
WEY  32  21  33  32 /   0  20  60  90
DLN  39  29  45  31 /   0  10  10  80
HVR  36  30  41  23 /   0  10  10  30
LWT  43  35  45  26 /   0   0   0  80

&&

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

&&

$$

http://www.weather.gov/greatfalls



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