textproduct: Great Falls

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

05/18Z TAF Period

The main concern will be low ceilings, along with showers/thunderstorms this afternoon through tonight. Most of the precipitation will be over the western portions of the CWA. On Sunday, expect lower ceilings, with more a steady rain developing over the western portions of North Central MT. The steady rain will start to be more of an impact over the eastern portions of North Central MT by Sunday night. Mountains/passes will be obscured at times by clouds/precip, especially later tonight and into Sunday.

For KGTF: The main concern for stronger winds in Great Falls will be from about 20z today thru 03z this evening with passing thunderstorms expected west of the Great Falls Airport. These passing thunderstorms could produce outflow wind gusts that could affect the Great Falls Airport. At this time, most wind gusts should remain less than 20 knots, but wind directions could be erratic with the gusts. Lower ceilings develop tonight and continue into Sunday, with a better chance for a more widespread light rain by Sunday night. Brusda

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.