textproduct: Great Falls

KEY MESSAGES

- Today through Friday there will be isolated showers and thunderstorms with some thunderstorms being strong to severe.

- It will be slightly cooler today.

- It will warm back up Thursday and Friday with a cooldown this weekend with widespread showers and thunderstorms.

DISCUSSION

/Issued 306 AM MDT Wed May 27 2026/

- Meteorological Overview:

Today the closed upper-level low remains over the Great Basin vicinity. Due to the cold front that moved through on Tuesday, today it will be slightly cooler but still above seasonal averages across North-central, Central, and Southwestern Montana. On Wednesday there will be enough instability and moisture for another round of showers and thunderstorms across the area. The strongest thunderstorms will produce gusty winds. On Thursday the closed low continues to sit over the Great Basin with a very subtle and slow eastward progression. With southerly flow aloft and some warm air advection temperatures will warm back up on Thursday. This will allow instability to build and lead to another round of showers and thunderstorms.

On Friday the upper-level low slowly weakens and transitions to an upper-level trough over the Great Basin. With southerly flow aloft on Friday temperatures will be hot. On Friday there will be another round of showers and thunderstorms. On Saturday an upper-level trough associated with a surface cold front moves over North- central, Central, and Southwestern Montana. This will cool down temperatures to near seasonal averages with widespread showers and thunderstorms. On Sunday the upper-level trough lifts northward. This allows temperatures to warm up slightly with lingering showers and thunderstorms. On Monday and Tuesday another closed upper-level low moves over/near Montana. This will bring about seasonal averages for temperatures with daily chances for showers and thunderstorms. -IG

- Forecast Confidence & Scenarios:

Today there is a 20 - 40% chance for thunderstorms across Central, and Southwestern Montana. Today the limiting factor for having the strongest and longest-lived thunderstorms is cloud cover in the morning combined with low wind shear. Today the strongest thunderstorms will be near mountain areas due to the limited shear. Today thunderstorms will produce heavy rain, gusty winds, small hail, and frequent lightning. On Thursday across most of North-central, Central, and Southwestern Montana there is a 10 - 30% chance for thunderstorms. On Thursday due to very low wind shear the risk for any strong thunderstorm is very low. However on Thursday there is enough instability that near terrain there is the potential for isolated slow moving thunderstorms.

On Friday there is a 20 - 35% chance for thunderstorms across most of North-central, Central, and Southwestern Montana. For Friday the Storm Prediction Center has issued a Marginal Risk (5% chance for wind gusts of 58 mph or greater and a 5% chance for hail with a diameter of 1 inch or greater within 25 miles of a point) for severe weather along and west of the I-15 corridor in North-central Montana. On Friday there is modest wind shear. This combined with good instability will lead to the greatest risk for severe thunderstorms out of the next three days (today, Thursday, Friday). On Saturday across North-central, Central, and Southwestern Montana there is greater than a 40% chance for thunderstorms.

On Friday there is a 20 - 40% chance for a tenth of an inch of rain or greater. Saturday through Sunday there is greater than a 70% chance for half an inch of rain or greater across most of North- central, Central, and Southwestern Montana. Saturday through Sunday there is greater than a 50% chance for 1 inch of rain or greater across most of North-central, Central, and Southwestern Montana.

Today across portions of Hill, Blaine, and Choteau Counties there is greater than a 80% chance for high temperatures of 90 degrees or greater. Today there is greater than a 60% chance for high temperatures of 95 degrees or greater across portions of Blaine County. Additionally with portions of Hill and Blaine Counties having lows in the lower 60s this morning a Heat Advisory remains in effect for Hill and Blaine Counties through this evening. On Thursday there is greater than a 75% chance for high temperatures of 90 degrees or greater across most of the lower-elevations of North- central Montana. On Friday there is a 50 - 80% chance for high temperatures of 90 degrees or greater across most of the lower- elevations of North-central Montana. On Thursday and Friday there is greater than a 50% chance for high temperatures of 95 degrees or greater across most of Hill and Blaine County. -IG

AVIATION

27/12Z TAF Period

VFR conditions will prevail across all terminals during this TAF Period. Showers and thunderstorms will begin to affect Southwestern Montana by around 27/18Z. Showers and thunderstorms will then move northward through the afternoon. By around 27/21Z showers and thunderstorms will begin to make it up to North-central Montana. All thunderstorms will produce frequent lightning and gusty, erratic winds. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 83 56 90 58 / 40 30 20 20 CTB 83 52 88 54 / 50 50 30 20 HLN 84 53 90 54 / 50 30 20 30 BZN 82 47 89 49 / 40 30 20 10 WYS 76 40 83 41 / 30 10 10 10 DLN 79 47 87 47 / 40 20 20 0 HVR 92 55 96 58 / 30 30 20 20 LWT 84 53 88 55 / 40 30 30 30

TFX WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 9 PM MDT this evening for Hill County- Northern Blaine County.