Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 181128

Area Forecast Discussion
National Weather Service Great Falls MT
430 AM MST Wed Jan 18 2017

Aviation Section Updated

Today through Friday...Main concerns in the short term will be
colder air trapped in the valleys of Southwest MT and light snow
Thursday night into Friday. Again, with some clearing last night
the valleys of Southwest MT have cooled off. Thus afternoon
temperatures today are below guidance a bit. Expect slightly below
guidance temperatures tonight/Thursday in these regions as well.
Over the north, it is mostly very mild for this time of the year.
Locations around Fort Benton, Cut Bank, and Fort Belknap are in
the upper 40s already this morning. Thus expect another mild
afternoon over the north. Wind speeds along the front range of the
Rockies are just below warning criteria, and that trend should
continue through this morning. Expect showers to affect locations
near the divide through the day. For tonight/Thursday, expect a
few passing light showers, mostly over the mountains as upper
level disturbances move through. Temperatures will be a bit cooler
over the region on Thursday as well. For Thursday night/Friday
morning, a stronger upper level disturbance combined with a
Pacific cold front will move through the region. The best chance
for widespread snow looks to be south of I90...with scattered
rain/snow showers as far north as Central MT. Overall, snow
accumulations look to range from 1 to 2 inches in the valleys from
Helena southward, to 2 to 4 inches in the mountains. (Little to
no snowfall is expected north of a line from Great Falls to
Lewistown.) An advisory might be needed for the Friday morning
commute for portions of Southwest MT. Temperatures will continue
to slowly cool a touch more for Friday afternoon. Brusda

Friday night through Wednesday...Have not made any significant
changes to the medium range forecast tonight and models continue
to be in relatively decent agreement through the period. Overall
trend for Montana weather favors seasonable temperatures with
breezy conditions across north central Montana. Models continue to
suggest that southwest Montana should also see a return to more
seasonable temperatures but I suspect that colder air may remain
trapped in this region so confidence in temperatures across the
southern half of the forecast area is low.

Period starts off with a broad upper level trough over western North
America. This trough will move through the Desert Southwest into the
southern Great Plains over the weekend. Shortwave ridging develops
over the Great Basin in the wake of this system but another broad
upper trough moves inland along the West Coast early next week. Once
again, the core of energy associated with this trough will remain
well south of Montana. Models move this system into the central and
northern Great Plains and end up developing a winter storm across
Nebraska and the Dakotas by Tuesday/Wednesday. Montana, however, is
expected to remain far removed from the active weather pattern and I
anticipate that models are not doing a very good job resolving the
location or timing for any shortwave energy that may pass through
the region. Have therefore continued a broad-brushed forecast that
favors scattered showers over the western mountains and southwest
Montana with only isolated to scattered showers over the plains. mpj


Updated 1130Z.
VFR conditions will prevail over the terminal sites through the
period. Expect breezy winds at times over North Central MT. Mid/high
clouds will affect the region through the period, with some showers
over the western mountains. The Rocky Mountain Front could be
obscured at times through the period. Brusda


GTF  48  34  43  30 /  10  10  40  20
CTB  47  27  43  26 /  10  10  20  10
HLN  32  15  30  19 /  10  10  30  30
BZN  31  14  34  18 /  10  10  20  40
WEY  22   1  23  14 /  10  30  40  50
DLN  37  20  33  18 /  10  20  20  40
HVR  46  29  41  29 /  10  10  10  20
LWT  47  31  43  28 /  10  10  10  40




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