Gallatin Gateway, Montana Weather Forecast Discussion

570
FXUS65 KTFX 141033
AFDTFX
Area Forecast Discussion
National Weather Service Great Falls MT
433 AM MDT Sun Sep 14 2025
Aviation Section Updated.
.KEY MESSAGES...
-  Mild today, with showers and thunderstorms mostly limited to the
   Continental Divide.
- Temperatures trend around ten degrees cooler in most areas for
   Monday as a period of rain moves across the region.
- Trending warmer and drier for Wednesday and most of Thursday.
&&
.DISCUSSION...
/Issued 131 AM MDT Sun Sep 14 2025/
- Meteorological Overview:
Broad troughing is in place across the interior western CONUS, with
slow moving embedded waves just north of the region in Canada as
well as across WY/CO. While both waves are at least relatively close
by, a quicker moving, more robust wave moving onshore across the
Pacific Northwest will be the main driver of weather today. The
arrival of the wave (Mainly late evening into tonight) is not timed
well with diurnal heating, so daytime shower and thunderstorm
coverage looks relatively minimal. There certainly will still be
showers and thunderstorms around however, most favored along the
Continental Divide late afternoon and into evening.
As the main portion of the wave approaches tonight, the combination
of forcing and sufficient elevated instability will result in a
period of showers and thunderstorms, most favored across Southwest
Montana.
The wave slows down/stalls across the region Monday into at least
Tuesday morning, which will keep opportunities for precipitation in
place across the region until it departs Tuesday afternoon or
evening. Temperatures Monday and Tuesday generally cool around 10
degrees or so (Plus or minus a bit in a few areas) compared to
Sunday.
A brief period of narrow, high amplitude ridging builds in for
Wednesday as the region is between upper level troughs. Wednesday
into Thursday looks dry as a result, with temperatures rebounding
back to near or a touch above average.
Confidence in the evolution of the pattern decreases significantly
toward Friday and the weekend. Confidence is moderately high for
troughing to be in place just off the Pacific NW coast Friday,
though there are significant discrepancies in the evolution of this
troughing (Whether it splits or not, as well as any interactions
with additional troughing that sneaks up the CA coastline). The main
takeaway at this point for Friday into the weekend will be for at
least low-end opportunities for afternoon and evening showers and
thunderstorms, with temperatures in the vicinity of average. -AM
- Forecast Confidence & Scenarios:
The Friday into the weekend timeframe is where the greatest
uncertainty lies. The difference between reasonable low-end and high-
end (10th to 90th percentile) high temperatures Friday and Saturday
is more than 20 degrees in many locations. Weaker/non-existant
troughing would favor the warmer solution, while a more robust, non
splitting trough would favor the cooler scenario. -AM
&&
.AVIATION...
VFR conditions will prevail throughout the 1412/1512 TAF period;
however, an approaching disturbance will bring increasing mid-
level cloud cover and precipitation chances to areas along the
Continental Divide and across Southwest Montana beyond 00z Monday.
Widespread mountain obscuration is not expected through 00z
Monday, but increasing obscuration is expected thereafter. -
Moldan
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF  81  52  70  53 /   0  20  40  60
CTB  79  52  67  48 /  10  20  50  50
HLN  80  51  67  50 /  10  50  60  40
BZN  79  45  65  44 /  10  30  60  30
WYS  68  35  57  32 /  10  30  70  20
DLN  74  42  61  40 /  20  60  60  20
HVR  83  53  75  53 /   0  10  20  50
LWT  78  50  69  49 /   0  20  50  60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls

NWS TFX Office Area Forecast Discussion