Area Forecast Discussion
Issued by NWS Great Falls, MT

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947
FXUS65 KTFX 152146
AFDTFX

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

.SYNOPSIS...

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.

&&

.DISCUSSION...

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.
Coulston

&&

.AVIATION...
Updated 1750Z.

MVFR/IFR conditions prevail in low ceilings at terminals along and
west of a line from KCTB to KBZN. KHVR and KLWT have cleared to VFR,
although KHVR has been reporting occasional IFR conditions in a
cold, icy haze. Forecast models indicate continued clearing, but
observations suggest persistent low cigs, especially in southwest
valleys. Thus, flight categories are expected to improve through
this afternoon, but with low confidence on timing. Freezing fog has
been added back into the KHVR forecast for early Tuesday. PN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF   5  38  27  41 /   0   0   0   0
CTB   2  36  25  38 /   0   0   0   0
HLN   6  29  16  33 /   0   0   0   0
BZN  -4  31  13  34 /   0   0   0   0
WEY  -7  29   9  29 /   0   0  10  10
DLN  15  37  21  38 /   0   0  10   0
HVR -13  15  10  35 /   0   0   0   0
LWT   4  36  23  41 /   0   0   0   0

&&

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

$$

http://www.weather.gov/greatfalls



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