textproduct: Great Falls

KEY MESSAGES

- Showers and thunderstorms will continue through this evening.

- Friday through Sunday it will be breezy across the area which will lead to elevated fire weather conditions across North- central Montana.

- Temperatures will cool down this weekend with showers and thunderstorms.

UPDATE

Early evening update is out. Isolated severe storms continue. The severe thunderstorm watch will continue for a bit. The plan is to expire the watch by 10 PM. At this time, we are not thinking of extending the watch unless storms become more widespread severe over the next hour. The airmass is cooling, thus the instability is decreasing, along with the threat for severe storms. Again the main impact from any severe storms this evening should be lightning and strong wind gusts.

Looking ahead, a slow cooling trend is beginning, with temperatures noticeably cooler by Sunday. Daily chances for showers/thunderstorms will continue, with the best chance for storms over Central and Southwest MT on Friday. Brusda

DISCUSSION

/Issued 403 PM MDT Thu Aug 27 2026/

- Meteorological Overview:

This afternoon there is an upper-level ridge over North-central, Central, and Southwestern Montana. It will be hot this afternoon across North-central, Central, and Southwestern Montana. An upper- level shortwave will move through the upper-level ridge and bring showers and thunderstorms to the area this afternoon and evening. See the Forecast Confidence & Scenarios section for details. On Friday the upper-level ridge begins to move east away from North- central, Central, and Southwestern Montana. As a result of the shortwave that moved through it will be slightly cooler across the area on Friday. Showers and thunderstorms will linger through much of the day on Friday across Southwestern Montana. Due to an increasing pressure gradient and approaching upper-level trough it will be breezy across North-central Montana on Friday.

On Saturday an upper-level trough associated with a Pacific Cold Front begins to move through North-central, Central, and Southwestern Montana. This brings cooler temperatures to the area with showers and thunderstorms. It will also be breezy on Saturday due to a strong pressure gradient. On Sunday the upper- level trough moves over North-central, Central, and Southwestern Montana. This will cool temperatures down more to well-below seasonal averages with another day of showers and thunderstorms. On Monday an upper-level ridge builds back in over North-central, Central, and Southwestern Montana. This will allow temperatures to warm back up with mostly dry weather. Tuesday through Wednesday an upper-level trough will move back over the area which will bring showers and thunderstorms back to the area on Tuesday and Wednesday. -IG

- Forecast Confidence & Scenarios:

Today the Storm Prediction Center (SPC) issued a Slight Risk (15% chance for winds gusts of 58 mph or greater) for severe thunderstorms across North-central Montana between I-90 and US Highway 2 west of Fergus and Blaine Counties. Across the rest of North-central, Central, and Southwestern Montana the SPC issued a Marginal Risk (5% chance for wind gusts of 58 mph or greater) for severe thunderstorms. This afternoon there will be deep inverted-V soundings with DCAPE values in excess of 1200 J/kg. The uncertainty with these storms this afternoon and evening is how the current line of storms moving through North-central Montana will affect the environment and if there will be clearing this afternoon before the next round of storms moves in to maximize the severe potential of any storms that form. If there is sufficient clearing then the strongest storms have the potential to produce outflow boundaries that produce wind gusts up to 75 mph.

On Friday there is a 15 - 30% chance for thunder in Southwestern Montana southeast of a Bozeman to Dillon line with the highest chances in the West Yellowstone area. On Saturday there is a 25 - 40% chance for thunder along and south of the Montana Highway 200 Corridor between Lincoln and Lewistown. On Saturday there is greater than a 60% chance for a quarter inch of rain or greater across Central and Southwestern Montana east of I-15. On Sunday across North-central Montana east of I-15 there is a 40 - 60% chance for a quarter inch of rain or greater. On Sunday there is a 50 - 70% chance for wind gusts of 40 mph or greater across most of North-central Montana. -IG

AVIATION

28/00Z TAF Period

Showers and thunderstorms will affect the CWA through at least 06z Fri, before slowly diminishing overnight. The main impact will be lightning/strong wind gusts. On Friday, expect another round of showers/thunderstorms to affect the CWA during the afternoon/evening hours, with storms beginning mostly after 20z Fri over far Southwest MT, moving towards Central MT by 00z Sat.

For KGTF : Main concern will be strong convective wind gusts with thunderstorms this evening. Current thinking is some storms could produce between 40 and 50 knot gusts with the storms as they move through. Overall, most of the storms / outflow wind gusts should exit the Great Falls area by 5z Fri. For now, thunderstorms are expected to remain just south of the Great Falls airport for Friday afternoon/evening. Brusda

FIRE WEATHER

Today there will be showers and thunderstorms across North-central Montana. All thunderstorms will produce frequent lightning amd gusty winds (outflows). Isolated thunderstorms will be on the drier side. It will also be hot this afternoon. This will lead to elevated fire weather conditions this afternoon. On Friday afternoon in Glacier County the HREF (Hi-res ensemble forecast) and the NBM have around a 50% chance for wind speeds of 15 mph or greater combined with relative humidity less than 20% (red flag criteria). Given those probabilities are only for less than half of the zone (FWZ 112) and that the Hot Dry Windy Index is below the 75th Percentile, no fire weather products will be issued. There will be elevated fire weather conditions across North- central Montana tomorrow. It will be breezy this weekend with showers and thunderstorms, but it will be cooler which will reduce the risk for fire weather concerns. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 58 86 59 77 / 40 10 20 60 CTB 55 82 51 73 / 30 0 0 30 HLN 54 82 54 76 / 40 20 30 80 BZN 53 79 51 76 / 40 40 50 70 WYS 45 70 42 65 / 40 70 90 90 DLN 53 78 50 76 / 30 30 50 70 HVR 60 90 58 83 / 40 10 10 10 LWT 57 83 55 76 / 40 20 30 50

TFX WATCHES/WARNINGS/ADVISORIES

None.