textproduct: Great Falls

KEY MESSAGES

- A cold front will bring northerly breezes, a brief cooldown, and mostly dry conditions today.

- Summer heat builds again and daily rounds of showers and thunderstorms return during the middle and end of the workweek with some storms containing strong wind gusts, hail, and torrential downpours capable of localized flooding.

- Drier and windier conditions move in for next weekend and increase fire weather concerns depending the quality of rainfall during the middle of the week.

DISCUSSION

/Issued 155 AM MDT Mon Jul 20 2026/

- Meteorological Overview:

A trough running along the Canadian border will send a Canadian surface front through the forecast area and will bring a northerly wind shift and a brief cooldown tonight into Monday. Moisture within the westerly flow aloft will maintain variable middle and higher level cloudiness and perhaps a few spotty light showers. Ridging aloft strengthens and brings a return to hot conditions heading towards the middle of the week. Emebedded shortwaves along the ridge are expected to interact with the monsoonal moisture leading to daily chances for showers and thunderstorms across the region, especially in Southwest Montana. The main concern, especially for Wednesday, will be an elevated chance for heavy rainfall which may lead to localized flash flooding.

Towards the weekend, the ridge axis moves eastward allowing for drier air to filter in and temperatures to warm across the region. There are hints in the models that this ridge could break down towards the weekend which would help moderate some of the currently forecasted highs but it would come at the price of windier conditions which may still lead to increase fire weather concerns. -thor

- Forecast Confidence & Scenarios:

Thunderstorm Potential Wednesday thru Friday:

Afternoon showers and thunderstorms are expected both on Wednesday and Thursday. The severe potential looks a bit marginal at the moment and will largely hinge on the timing of the trough. There is a concern that PWATs are running a bit high (>1.25" across much of the region) which has been further confirmed by the strong signal on the NAEFS. The main impact from this would be localized flash flooding as well as the standard thunderstorm threats of lightning, hail, and strong winds.

Towards Friday, the threat for thunderstorms continues but the moisture content goes down quite a bit compared to Wednesday and Thursday. This opens the door for more of a threat for drier thunderstorms which, combined with hotter temperatures and lower minimum RH values, may increase the fire weather concerns for that afternoon. -thor

Gusty Winds and Elevated Fire Weather Conditions on Friday and Saturday...

Cross barrier flow will begin to increase through the end of the work week and into the weekend as upper level ridging flattens, with H700 winds increasing to between 25-35kts which is 1 to nearly 2 standard deviations above normal for the Rocky Mountain Front. NBM5.0 probabilities support a 35-70% chance for wind gusts to exceed 34kts on both days, with a 10-30% chance to exceed 43kts. These gusty winds combined with hot temperatures will lead to elevated fire weather conditions along the entire Rocky Mountain Front, most notably across Fire Weather Zones 112. - Moldan

AVIATION

20/12Z TAF Period

A surface high north of the Canadian border will maintain northerly breezes for much of the period while variable high and middle level clouds stream in from the west. Other that a few spotty light showers and sprinkles today, VFR and dry conditions will prevail. There may also be some lingering wildfire smoke aloft that may compromise slantwise visibility at times. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 84 61 86 60 / 10 10 0 0 CTB 80 57 81 57 / 0 10 0 0 HLN 87 61 88 63 / 10 0 20 10 BZN 90 58 89 59 / 0 0 10 10 WYS 90 50 87 52 / 10 10 50 40 DLN 87 55 84 57 / 10 10 20 20 HVR 86 58 86 60 / 0 0 0 10 LWT 82 55 82 55 / 0 0 10 0

TFX WATCHES/WARNINGS/ADVISORIES

None.