Lima, Montana Weather Forecast Discussion

954
FXUS65 KTFX 190725
AFDTFX
Area Forecast Discussion
National Weather Service Great Falls MT
125 AM MDT Fri Sep 19 2025
.KEY MESSAGES...
- General warm and dry conditions are expected through Saturday.
- A Pacific weather system will bring breezy to windy conditions
  and increased shower and thunderstorm activity Sunday and
  Monday.
- Drier and warmer conditions return for the mid- week period.
&&
.DISCUSSION...
- Meteorological Overview:
Ridging aloft will generally maintain warm and dry conditions for
the next few days, but there will be a few caveats. Firstly, the
mid- level low that has been drifting through eastern MT may be
sending another wave of lower stratus and patchy fog into the
forecast area this morning. Similar to yesterday, this will be
mostly confined to the Milk River Valley area between 6 am and
noon today. Then a weak shortwave undercuts the ridge this
afternoon and evening. This feature will offer little change to
the sensible weather other than increased mid- and higher level
cloudiness and perhaps a few stray showers or thunderstorms,
mostly along the Continental Divide/Rocky Mountain Front.
The long advertised Pacific trough and cold front then arrives
Sunday into Monday. Previous model runs were highlighting the
system moving through as an open wave in a west to east fashion,
but newer runs slow the system`s progression and favor a more
southeasterly trek of the trough axis with it becoming closed off
from the general flow. These newer solutions decrease winds
slightly, but introduce more precipitation, mostly for central and
southwestern locations. H700/H500 temperatures down to as low as
0C/-15C will also introduce some light snow to the higher mountain
peaks of the southwest Monday morning, generally above 7,500 to
8,000 ft.
Ensembles widely support ridging aloft becoming reestablished
over the Northern Rockies and yielding dry conditions and above
normal temperatures by the mid-week period. Troughing does look to
move into the Pacific Northwest heading towards the latter part
of next week for cooling temperatures, breezy conditions, and
perhaps some precipitation chances, but there are differences in
timing and depth of the shortwaves/troughs responsible for the
said unsettled conditions. - RCG
- Forecast Confidence & Scenarios:
Increased winds, shower and thunderstorm activity, and cooler
temperatures late this weekend into early next week...
The latest model guidance has begun to shift towards a slower and
less zonal path for this weekend`s trough, which generally favors
a little less wind and more precipitation. Westerly winds will
still be on the gustier side due to the passage of a surface
front, especially compared to recent days. NBM wind exceedence
probabilities for gusts over 50 mph Saturday night and Sunday are
currently running between 60 and 80% for Northern Rocky Mountain
Front locations west of highway 89 and over 90% along immediate
eastern slopes of the front range itself. Winds over the plains on
Sunday will generally be gusting in the 30 to 40 mph range,
except in the Cut Bank area where there`s around a 40% chance for
gusts over 50 mph. Impacts will mostly be limited to those
operating recreational vehicles in and out of Glacier National
Park and other outdoor activities in and near the park.
Shower and thunderstorm activity will be more prevalent if this
system does indeed slow down and take a more southeasterly path.
Around half of the ensembles favor more residence time over
Southwest MT, resulting in more precipitation there. Probabilities
for a rainfall totals over a quarter inch for the 48 hour period
ending Monday night are now running between 20 and 40% for central
and southwestern lower elevation locations southeast of a Helena
to Lewistown line. The Madison and Gallatin ranges and the
Bridgers have 30 to 50% probabilities for a half inch of
precipitation for the same timeframe. Since this will be a cold
core low, a dusting of snowfall can be expected for elevations
above 7,500 to 8,000 ft Monday morning. Overall, the cooldown with
this system doesn`t look overly impressive with temperatures only
briefly cooling to slightly below average, coolest on Monday.
Temperatures rebound back above average by mid-week amid the
rebuilding of the ridge. - RCG
&&
.AVIATION...
19/06Z TAF Period
While VFR conditions are expected to prevail over the next 24
hours, there is a chance of some fog and/or low stratus developing
in and around the KHVR area around sunrise. Otherwise, expect just
some high clouds and light winds for the next 24 hours. Ludwig
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF  79  48  85  51 /   0   0   0   0
CTB  77  45  83  47 /  10  10   0   0
HLN  79  49  83  52 /   0   0   0   0
BZN  78  45  82  47 /   0   0   0   0
WYS  72  34  73  37 /   0   0  10  10
DLN  76  43  80  45 /   0   0   0  10
HVR  78  48  84  50 /  10  10   0   0
LWT  75  48  81  50 /   0   0   0   0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls

NWS TFX Office Area Forecast Discussion