Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 160557

Area Forecast Discussion
National Weather Service Great Falls MT
1055 PM MST Mon Jan 15 2018



Temperatures are falling quite rapidly across N-central MT already
this evening with Havre by far the coldest and already down to -26
by 630pm. Also getting some reports of localized freezing fog and
light snow/flurries on the N and E side of Great Falls as an area
of shallow low clouds moves westward. A fairly extensive low
cloud deck extends north along the Rocky Mtn front and with light
east to southeast flow continuing through late this evening likely
to generate some light flurries due to upslope influence will add
flurries in addition to areas of freezing fog to these areas.



High pressure will maintain mostly clear skies overnight into
Tuesday. However, low clouds and fog may persist in some southwest
valleys. Overnight lows will fall into the single digits above
and below zero for most of the area. Breezy westerly winds will
help warm most of the area back closer to normal for Tuesday.


Updated 0555Z.

VFR conditions are expected for most of the area through the next 24
hours due to high pressure aloft. However, shallow lower clouds with
patchy fog and areas of IFR/LIFR conditions will persist at least
overnight, possibly into Tuesday morning, along the Rocky Mountain
Front (including KCTB) south into the southwest valleys (including
KHLN KBZN KEKS KDLN). Winds will gradually shift more southerly and
increase across the area during the day on Tuesday, which will help
scour out the low clouds. An approaching upper level trough will
then bring increasing mid and high cloudiness with a chance of
mountain precipitation to the area after 18Z.


/ISSUED 445 PM MST Mon Jan 15 2018/

Tonight through Wednesday...The cold air mass that backed into
North-central MT is already beginning to drift away to the east.
Low clouds across western portions of the North-central plains
continue to thin as dry air arrives on a northerly flow aloft.
Although temperatures are not as cold in the southwest valleys,
persistent low clouds will likely remain in those valleys at least
overnight. Clearing skies and dry air aloft will increase net
radiative cooling and result in very cold temperatures over the
North-central plains. Skies remain clear on Tuesday as the Arctic
surface high moves away, forming a lee-side surface trough along
the Rocky Mountain Front. Breezy southwest winds will then
translate down to the plains on Tuesday, which will help warm up
temperatures there back closer to normal. However, the colder air
will be slower to scour out of the northeast TFX plains (including
the Havre area). A weak disturbance in a more westerly flow aloft
will bring a good chance of precipitation to the mountains
Tuesday afternoon into Tuesday night, but the gusty westerly
downslope winds will keep the plains and valleys dry through
Wednesday, as temperatures generally warm above normal. PN/Coulston

Wednesday Night through Monday...Another shortwave trough will
move through the westerly flow aloft Wednesday night into
Thursday, bringing another round of mountain precipitation.
However, this shortwave will move more so along the Canadian
border, which may cause strong winds over the plains, especially
along the Rocky Mountain Front. Will monitor this for potential
high wind highlights. Temperatures will also remain well above
normal during this time. A cold front will move southeast through
the forecast area in the wake of this shortwave Thursday night
into Friday, which will bring a very good chance for accumulating
snow in the mountains. Will keep an eye on this for potential
winter weather highlights. A large upper level low pressure
trough will then move over the western United States for Friday
through Monday. As a result, temperatures will cool to well below
normal for the weekend with a chance of additional light snow for
most of the period.


GTF  -1  38  27  41 /   0   0   0   0
CTB   2  36  25  38 /  10   0   0   0
HLN   7  29  16  33 /   0   0   0   0
BZN   1  31  13  34 /   0   0   0   0
WEY  -4  29   9  29 /   0   0  10  10
DLN  17  37  21  38 /   0   0  10   0
HVR -32  15  10  35 /   0   0   0   0
LWT   2  36  23  41 /   0   0   0   0



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