textproduct: Great Falls

KEY MESSAGES

- It will be hot, dry, and hazy through Tuesday.

- A brief cool down is expected Wednesday through next Friday with isolated showers and thunderstorms returning to the area.

- This weekend there will be isolated showers and thunderstorms with warmer temperatures.

DISCUSSION

/Issued 151 PM MDT Mon Aug 10 2026/

- Meteorological Overview:

This afternoon there is an upper-level ridge over North-central, Central, and Southwestern Montana. This will keep warm and mostly dry weather for the area on Monday. Isolated showers have the potential to slide south from Canada and affect the Hi-Line this afternoon and evening. On Tuesday the upper-level ridge remains over North-central, Central, and Southwestern Monday. This will will keep warm and mostly dry weather for the area on Tuesday. Isolated showers have the potential to slide south from Canada and affect the Hi-Line Tuesday afternoon and evening. On Wednesday the upper-level ridge remains over North-central, Central, and Southwestern Montana with an upper-level trough approaching the area. This will begin to bring cooler air and monsoonal moisture to the area on Wednesday. On Wednesday there will be showers and thunderstorms along the Hi-Line.

Thursday through Friday an upper-level trough moves over North- central, Central, and Southwestern Montana. This will bring showers and thunderstorms and cooler temperatures (well-below seasonal averages) to the area Thursday through Friday. See the Forecast Confidence & Scenarios section for details. This weekend an upper-level ridge builds back in over North-central, Central, and Southwestern Montana with southwest flow aloft. This will bring daily chances for showers and thunderstorms with temperatures warming up on Saturday and Sunday. -IG

- Forecast Confidence & Scenarios:

This afternoon and tomorrow afternoon across North-central, Central, and Southwestern Montana minimum afternoon humidity will be near critical levels. This combined with winds that will be around 20 mph will bring elevated fire weather conditions to the area. The wind direction will also periodically shift over the next 24 hours. The greatest risk for elevated to near critical fire weather conditions will be in Southwestern Montana this afternoon and tomorrow afternoon.

Wednesday through Friday there is good agreement between ensemble members and deterministic models in the track of the upper-level trough. On Wednesday there is a 20 - 35% chance for thunderstorms across North-central, Central, and Southwestern Montana. On Thursday there is a 30 - 50% chance for thunderstorms across North-central, Central, and Southwestern Montana. On Friday there is a 35 - 55% chance for thunderstorms across Central and Southwestern Montana. Wednesday through Friday there is a 50 - 80% chance for one half inch of rain or greater across North- central, Central, and Southwestern Montana with the highest probabilities along the Hi-Line. Wednesday through Friday there is a 50 - 70% chance for one inch of rain or greater along the Hi- Line and across Judith Basin and Fergus Counties. On Thursday and Friday there is greater than a 60% chance for high temperatures of 70 degrees or lower across the plains of North-central Montana. -IG

AVIATION

11/00Z TAF Period

Ridging aloft will maintain dry and seasonably breezy conditions. The primary concern will be smoke and haze impacting slantwise visibility and bringing periodic MVFR vis and cigs, especially for the southwest MT terminals. A weak surface boundary will bring a northerly wind shift tonight into Tuesday over the plains. There will be ongoing convection north of the Canadian border that will begin to sag southward towards the Hi- Line terminals at the end of the TAF period.

For KGTF: Winds will remain light and variable for the overnight period. A weak surface boundary will bring a northwesterly wind shift sometime between 11/10 and 11/15Z. Brief wind gusts up to 20 kts can't be ruled out during the day on Tuesday, but the probability of occurrence is less than 15%. Otherwise, the smoke and haze reducing slantwise visibility will the main aviation concern. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 54 86 54 77 / 0 0 0 0 CTB 50 79 49 67 / 0 0 40 50 HLN 54 89 54 80 / 0 0 0 20 BZN 52 90 52 85 / 0 0 10 10 WYS 42 85 45 79 / 0 0 0 10 DLN 50 88 52 83 / 0 0 0 10 HVR 53 86 52 78 / 20 0 20 40 LWT 52 83 51 76 / 0 0 0 30

TFX WATCHES/WARNINGS/ADVISORIES

None.