Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 171012
AFDTFX

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

.SYNOPSIS...

Weak high pressure aloft will keep the region dry today into
tonight, as increasing westerly winds help warm temperatures above
normal through Thursday. The next Pacific weather system will then
bring light measurable snow to the Rocky Mountain Front and to areas
along and south of a Great Falls to Lewistown line Thursday through
Friday. Snowfall amounts above mountain pass level will likely be in
the 6 to 12 inch range. Colder than normal temperatures with an
unsettled weather pattern is then expected in the wake of this
system for this weekend.

&&

.DISCUSSION...

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

&&

.AVIATION...
Updated 0620Z.

VFR conditions are generally expected to continue for the next 24
hours or so, but fog still trapped in the Helena valley may cause
periods of low MVFR/high IFR visibilities at KHLN between 09Z and
17Z. Otherwise, weak disturbances in the westerly flow aloft will
move areas of mid and high clouds over the area and spread gusty
southwest winds from KCTB and KGTF east through KHVR and KLWT
overnight.  Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  43  39  47  29 /   0  10  10  60
CTB  40  35  43  29 /  10  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 /  10  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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