631
FXUS65 KTFX 051524
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
924 AM MDT Sat Sep 5 2026

.KEY MESSAGES...

 - Showers and thunderstorms will push through Montana on Sunday,
   some of which may bring some gusty winds.

 - Widespread soaking rainfall expected Sunday through Tuesday, with
   some areas on the Hi-Line having a 40-60 percent chance of seeing
   2 inches of rainfall.

 - Temperatures start next week below average, before returning
   to near average for the second half of the week.

&&

.Update...
Current forecast is on track, no updates planned for this morning.
Light rain showers continue to move northward through mostly the
northern portions of the CWA this morning. Rainfall is light,
generally less than 0.05 inches. Temperatures will be a bit cooler
today. Even cooler temperatures for Sun/Mon, along with a better
chance for more widespread rain and thunderstorms. Brusda

&&

.DISCUSSION...
/Issued 200 AM MDT Sat Sep 5 2026/

 - Meteorological Overview:

A deep and slow moving upper level trough over the Eastern
Pacific/Western US will slowly move eastward over the coming days.
As it moves eastward, expect rain along the Continental Divide
today to slowly shift eastward and expand, with more widespread
showers and thunderstorms Sunday, Monday, and early Tuesday before
this system departs late Tuesday morning and Wednesday. Behind
this system, drier weather is expected Wednesday and Thursday as
weak upper level ridging transits the area, which will also bring
temperatures back closer to average after a cool start to the
week. However, more unsettled weather looks likely to close out
the week as yet another upper level trough pushes into the Western
US.

 - Forecast Confidence & Scenarios:

Thunderstorms Sunday: Recent Hi Res model guidance has begun to
hint at the possibility of a round of thunderstorms on Sunday
capable of producing some strong to severe wind gusts. While it
does not currently look quite as damaging as Wednesdays event
was, there are still a few things to note about the severe threat.
Model soundings and hodographs (temperature/humidity profiles and
wind profiles, respectively) show quite a bit of instability in
the mid/upper levels, along with ample shear to help storms form
and then organize and strengthen as they race northeastward thanks
to relatively strong winds (in excess of 50 knots/60 mph). Given
the wet environment, it will be difficult for any larger hail to
reach the surface, but some smaller hail may still reach the
surface. Winds are a bit tricky as well, as while there is both
sufficient dry air near the surface and winds aloft to result in
some strong wind gusts, there are also hints of some capping which
may limit transport of the winds to the surface. Given the
uncertainty, SPC has placed much of North Central and Central
Montana on Sunday, which seems reasonable at the moment given the
uncertainty.

Rainfall through Tuesday: Models remain fairly consistent on a
period of widespread soaking rainfall across North Central and
Southwestern Montana through Tuesday. Most models also remain
consistent in placing the heaviest precipitation north of a Helena
to Great Falls to Lewistown Line, where amounts of 1to 2 inches
appear likely. However, there remains some possibility that some
areas could see more significant rainfall totals (in excess of 3 or
4 inches), which could result in some increases to rivers and
streams. Widespread flooding remains unlikely, though some areas
could see some ponding of poor drainage areas. Ludwig

&&

.AVIATION...
05/12Z TAF Period

Scattered rain showers will continue this morning with minor
impacts possible for KGTF, KCTB, and KLWT. For areas along and
west of the I-15 corridor, low stratus is expected to linger
through this morning before another round of moisture is expected
Saturday afternoon. Mountain obscuration will be an ongoing
concern along the Continental Divide through the period. While
rainfall this afternoon and evening should remain west of most TAF
sites, rain and low ceilings will begin to work into the area by
early Sunday morning.

Otherwise there are some concerns that fog could develop at both
KBZN and KWYS right around sunrise but confidence in the exact
impact and timing was remains too low to include it in the TAF.

For KGTF: VFR conditions will prevail through the period with a
low stratus deck expected to linger through at least the mid-
morning hours. Winds in the early afternoon will start to pick up
out of the east/northeast with gusts up to 20kts possible.
Overall the risk for exceeding the crosswind threshold is rather
low at around 15%. The time frames to watch for will be right as
the winds start to increase out of the east towards the early
afternoon and then as showers and thunderstorms move through which
may produce gusty/erratic winds at times. The main threat for
thunderstorms at KGTF will be between 06/00Z and 06/05Z.
-thor/Ludwig

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  73  50  73  51 /  10  30  10  90
CTB  65  46  63  46 /  70  90  80  80
HLN  76  49  77  52 /  10  20  10  70
BZN  79  46  82  49 /   0   0   0  60
WYS  72  38  75  40 /   0   0   0  80
DLN  78  43  80  46 /   0   0   0  70
HVR  79  51  77  51 /  10  10  50  90
LWT  76  49  79  50 /   0   0  20  90

&&

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

&&

$$
http://www.weather.gov/greatfalls