textproduct: Great Falls

KEY MESSAGES

- Slight chances for showers and thunderstorms this afternoon through this evening across the region.

- More widespread precipitation tomorrow through Thursday.

- Snow levels drop Wednesday night into Thursday, allowing for light snowfall accumulation in the mountains.

- Warm and dry conditions are expected Friday through this weekend.

DISCUSSION

/Issued 1249 PM MDT Tue May 19 2026/

- Meteorological Overview:

Residual moisture from the backside of an upper level trough exiting to the east will bring slight chances for precipitation this afternoon through this evening. There is enough instability to support weak thunderstorm development, especially in Central and North-central MT. Another upper level trough moves down from the Canadian Rockies into Montana tomorrow, bringing widespread wetting precipitation. There will still be enough instability to where a rumble of thunder could be heard across the region. A weak cold front passing through tomorrow night will cause snow levels to drop to around 6,000 ft. This will allow for light snowfall over the mountains and higher elevation mountain passes tomorrow night through Thursday morning. The exceptions are the Gallatin and Madison ranges, which could see a few inches.

Thursday the upper level trough begins to move southeastward out of MT, allowing temperatures to begin to rise. Ridging builds over the western CONUS through the later part of this work week into the weekend, allowing warm temperatures, sunny skies, and dry conditions to prevail. Current models are showing breezy conditions this weekend, but as of now nothing impactful. -Dzomba

- Forecast Confidence & Scenarios:

Hi-res models are showing pretty scattered 15-30% chances for precipitation across the region today. In general, most locations will remain dry throughout the day except for where these pop-up showers end up developing. The highest chances for thunderstorm activity will be across Central and North-Central MT

There is still good agreement for widespread wetting rains tomorrow. The heaviest amounts are currently expected along a stretch from the Northern Rockies down through Central MT including Great Falls and Helena into Lewistown. Probabilities of more than 0.10" of precipitation in this area are currently 80-100%, while probabilities of 0.25" of precipitation are currently sitting at 50-70%. While precipitation amounts across the remainder of North-Central and Southwest MT are not expected to be quite as high, there is still a 20-40% chance for a tenth of an inch or more. -thor and Dzomba

AVIATION

20/00z TAF Period

Scattered showers will start to wind down between 20/01z to 20/03z, with a few isolated showers lingering through Wednesday morning. A cold front Wednesday will bring a northwest wind shift along with scattered to widespread showers. Weak instability will allow for some isolated thunderstorms to develop, but it will be a hit or miss across terminals. The front will also bring lowering ceilings to MVFR at times Wednesday. -Wilson

PRELIMINARY POINT TEMPS/POPS

GTF 39 57 38 61 / 20 90 60 20 CTB 38 54 34 62 / 10 80 50 0 HLN 38 64 38 61 / 20 60 90 30 BZN 33 62 35 55 / 20 20 100 70 WYS 26 57 30 51 / 10 30 90 60 DLN 34 62 35 57 / 20 10 90 40 HVR 39 62 35 65 / 30 60 20 10 LWT 35 58 35 55 / 20 80 70 40

TFX WATCHES/WARNINGS/ADVISORIES

None.