Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 191722

Area Forecast Discussion
National Weather Service Great Falls MT
1021 AM MST Fri Jan 19 2018



An area of frontogenesis aloft over southern portions of Central
MT and Southwest MT will continue to shift southward and eastward
today as the Pacific front continues to do the same. Accordingly,
the associated light to occasionally moderate snow will gradually
taper-off from northwest to southeast over the same areas. Since
additional snow accumulations are expected to be no more than 1 to
3 inches through this afternoon, decided to cancel the winter
weather advisory for Southwest MT and parts of Central MT. Also
freshened our temperature grids through this early evening. Latest
observations from most locations have been several degrees warmer
than the majority of model guidance. Thus, used a consensus of
short term model guidance, which has had the best handle on the
temperature situation. This increased temperatures, including
highs, by up to several degrees for most places. This seems
plausible since abundant cloud cover and weak cold advection
behind the recent cold frontal passage should limit daytime
heating today.


Areas of light snow will continue to affect southern portions of
Central Montana this morning and most of Southwest Montana today
and tonight. Cooler temperatures will prevail through the weekend
and into next week with a chance of snow showers continuing along
the Continental Divide.


Updated 1721Z.

Westerly flow aloft expected next 24-hours as a Pacific disturbance
continues to approach from the west. VFR are expected to grace North-
Central MT throughout the period, but breezy SW to W surface winds
will occur, especially along the Rocky Mountain Front, including
KCTB. Periods of upslope snow and mountain obscuration will persist
along the Continental Divide. Across SW MT, including KEKS and KBZN,
the upper reaches of a Pacific front and associated snow will
gradually clear the area from NW to SE this afternoon and tonight,
with snow likely exiting the region completely between 06Z and
09Z/Sat. CIGS and VSBY associated with this snow will likely vary
between MVFR and LIFR. Lastly, as partial clearing of skies occurs
behind the snow, patchy freezing fog may develop in the valleys of
SW MT around daybreak Saturday.


/ISSUED 437 AM MST Fri Jan 19 2018/

Today through Sunday...Upper level disturbance continues to bring
light rain and snow (and a few areas of freezing rain) to southern
portions of Central Montana and much of Southwest Montana. This
feature will continue moving to the southeast with precipitation
tapering off in Central Montana but continuing overnight in
Southwest Montana. Core of the upper level trough will remain well
south of Montana through the weekend with generally weak west to
northwest flow aloft prevailing over the Northern Rockies. Breezy
westerly winds will allow mostly dry and cool conditions to
continue over the plains but a chance for precipitation will
linger over the Continental Divide. mpj

Sunday night through Friday...Medium range models are in decent
agreement suggesting that a progressive flow aloft will prevail
over the region through much of next week. Period will start off
with a closed upper level low over the Southern Rockies and
shortwave ridging over Montana. The closed low will lift
northeastward into the Midwest while Montana is expected to see a
series of weak shortwave troughs and ridges pass through the
region through midweek. Abundant Pacific moisture will bring
periods of snow to the western and Southwest Montana mountains
while isolated showers occasionally move out over the plains. From
Wednesday through Friday the region will see a transition to
cooler temperatures as a broad upper level trough moves inland
over the western USA. Models continue to suggest that bulk of
energy associated with this trough will remain mainly south of
Montana but this will continue to be watched for any signs of
models trending further north over the coming days. mpj


GTF  39  26  35  20 /  20  10   0  10
CTB  36  26  35  19 /   0  10  10  10
HLN  34  14  27  10 /  40  10  10  10
BZN  33  10  26   7 / 100  30  10  10
WEY  32   4  24  -3 / 100  60  10  10
DLN  34  15  26   9 /  50  20  10  10
HVR  37  20  29  11 /  10  10   0  10
LWT  35  19  32  15 /  60  10   0  10



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