textproduct: Great Falls

KEY MESSAGES

- Below normal temperatures today will moderate from Tuesday through Friday, with the warmest days of the upcoming week occurring on Thursday and Friday.

- Outside of Tuesday and Wednesday their will be daily chances for precipitation, most notably from Thursday through the upcoming weekend.

- Strong and gusty winds are possible on Friday across Southwest Montana.

- A cool and wet weekend is possible across all of the Northern Rockies.

DISCUSSION

/Issued 1206 AM MDT Mon Jun 22 2026/

- Meteorological Overview:

Moist and unstable northwest flow aloft will help to maintain showers, thunderstorms, and below normal temperatures across Southwest through North Central Montana today, with precipitation coverage gradually waning through the evening hours tonight as the upper level flow backs to the west as upper level ridging begins to build and slide east over the Northern Rockies. This upper level ridge will bring moderating temperatures from Tuesday through Friday, with Thursday or Friday being the warmest days of the upcoming week as warm air surges north of an approaching upper level trough. While most areas will remain dry on Tuesday and Wednesday as the upper level ridge axis moves overhead an isolated shower or thunderstorm can't be ruled out, mainly over the higher terrain. By Thursday and Friday Pacific moisture will begin to stream northeast and over the Northern Rockies as the upper level flow backs to the southwest, which will help to support scattered to numerous showers and thunderstorms across Southwest through North Central Montana. A few of the thunderstorms on Thursday and Friday could be on the stronger side as both instability and shear increase across the region. As the upper level trough swings east and over the Northern Rockies this upcoming weekend precipitation will become more widespread, with temperatures falling below to well below normal. - Moldan

- Forecast Confidence & Scenarios:

Strong and Gusty Winds on Friday...

Climate anomaly indicators such as the ECMWF EFIs and NAEFS are indicating the potential for a climatologically unusual, with respect to late June climatology, wind event across Southwest Montana. H700 winds of 20-40kts from the south to southwest per NAEFS analysis combined with the south-north valley orientation and/or deep mixing will support strong surface winds across all elevations south of the I-90 corridor from the late morning through earl evening hours on Friday, especially within the the Madison and Beaverhead Valleys. BUFKIT sounding for these respective valleys shows afternoon mixing heights of between 5000-10,000ft agl, which will support higher end momentum transfer to the surface, which combined with the effects of terrain funneling will help to enhance surface wind speeds/gusts. Latest NBM5.0 probabilities with respect to wind speeds of 30 mph or greater for areas south of the I-90 corridor range from a 40-60% chance across most areas, with a 5-15% chance that sustained wind speeds reach 40 mph within the Dillon, Ennis, and Norris Hill areas. Additionally, latest NBM5.0 probabilities with respect to wind gusts of 50 mph or greater for most areas south of the I-90 corridor range from a 20-60% chance, with a 5-10% chance that gusts exceed 60 mph within the Beaverhead and Madison Valleys. This potential strong wind event will need to be monitored given the increased summer traffic across the area as strong cross winds will pose a threat to those operating high profile vehicles.

Wet and Cool Conditions this Weekend...

Cluster analysis is favoring and anomalies upper level trough digging in over the Northern Rockies over the period, with the main mode of uncertainty being the position and/or timing of the trough as it moves over the region. This position and/or timing uncertainty will ultimately impact where and when the heaviest precipitation falls, but latest NBM5.0 probabilities support a 40-80% chance for 48hr (6am Saturday through 6am Monday) rainfall amounts to exceed 0.5" across all of Southwest through North Central Montana, with a 20-40% chance that amounts exceed 1" across most areas outside of the Glacier National Park, Little Belts, and Madison/Gallatin Range areas where there is a 40-70% chance of exceeding 1". While below normal temperatures are likely to occur on both Saturday and Sunday beneath this upper level trough there is a 30-50% chance that highs on Sunday will fail to reach 60 degrees, with even a 10-30% chance that the higher elevations of Continental Divide fail to reach 32 degrees. - Moldan

AVIATION

22/12Z TAF Period

Scattered to numerous showers and isolated thunderstorms will continue across portions of Southwest through North Central Montana through 03-06z Tuesday, with the highest coverage of precipitation occurring along and south of the Montana Hwy 200 and north of the US Hwy 12 corridor. A few of the thunderstorms near the KLWT terminal could become strong and produce gusty winds and hail, especially between 18-24z this afternoon. Outside of the KBZN, KEKS, KWYS, and KHLN terminals where VFR conditions are expected throughout the next 24 hours IFR/MVFR/low-VFR conditions will occur through 04-07z Tuesday at the remaining terminals. Mountains north of the I-90 corridor will be obscured through 03-09z Tuesday. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 64 41 70 47 / 40 20 0 0 CTB 58 37 68 45 / 30 0 0 0 HLN 69 43 74 49 / 30 20 0 0 BZN 73 40 75 45 / 20 20 0 0 WYS 71 33 72 36 / 0 0 0 0 DLN 75 40 75 43 / 0 0 0 0 HVR 66 44 70 45 / 40 20 0 0 LWT 62 38 66 43 / 80 20 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.