textproduct: Great Falls

KEY MESSAGES

- Very warm temperatures through the week with the hottest temperatures expected across the Northern Plains.

- Daily chances for showers and thunderstorms through the week. A few may become severe with the main threat being strong wind and hail.

DISCUSSION

/Issued 1252 AM MDT Tue May 26 2026/

- Meteorological Overview:

Well above normal temperatures will continue through the rest of the week with highs remaining above 80 through at least Friday. The upper-level trough will migrate south this afternoon with the associated low starting to become more cutoff by Thursday morning. Throughout the rest of the week it will largely remain in this area, ejecting multiple shortwaves out towards Montana which will allow for daily chances for showers and thunderstorms. There is a chance a few storms may turn severe with the primary threat being strong winds and a secondary threat of hail.

- Forecast Confidence & Scenarios:

Heat this Week:

Tuesday is generally expected to be the hottest day across the region with many lower elevation locations reaching the upper 80s to upper 90s.

The main concern with Tuesday through Wednesday is that across northern Blaine county the overnight lows are only expected to dip down into the mid 60s which when sandwiched between two mid to upper 90 degree days could create additional heat stress for those living in the area. Considering the potential impacts, the decision was made to put northern Blaine county in a Heat Advisory through Wednesday.

Additional locations across North-Central Montana are near advisory criteria but given that there is enough confidence in temperatures cooling off sufficiently overnight, no additional zones were added at this time. But folks in Hill and Chouteau counties should be prepared for very warm temperatures and the potential threat for heat-related illnesses, especially for those spending a significant time outdoors. Additionally, there are heat-related concerns along the Upper Missouri Breaks such that anyone recreating in that area should be prepared for poor overnight temperature recovery, particularly along the lower valley which could cause additional stress if recreating.

Warm temperatures will continue across North-Central Montana through the rest of the work week. For now, given the levels of uncertainty with how hot it will get each day and how cool it will get each night, no additional products will be issued at this time. But folks should be prepared for the longest stretch of 90+ degree weather we have had so far this year.

Thunderstorms Chances this Week:

For Tuesday afternoon, there is some persisting uncertainty as to how moist it will get and whether the moisture will arrive in time to impact convective development. The moisture profile generally looks better Wednesday through Friday as the southerly flow continues to work some moist air into the region. Throughout this week the bulk of the uncertainty will revolve around whether the highest instability is able to overlap with the highest shear which would create a higher potential for severe weather. In the case where shear remains lacking, there is a concern that storms may still form but without a driving force they may linger over an area for too long and become more of a flash flood threat. -thor

AVIATION

26/12Z TAF Period

VFR conditions will prevail across all terminals during this TAF Period. Showers and thunderstorms will affect all terminals during this TAF Period. Showers and thunderstorms will begin to affect Southwestern Montana between 26/17Z and 26/20Z. Showers and thunderstorms will then move northward through the afternoon. By around 27/01Z showers and thunderstorms will begin to make it up to North-central Montana. All thunderstorms will produce frequent lightning and gusty, erratic winds. The strongest thunderstorms will produce small hail and wind gusts in excess of 50 kts. During this TAF Period there will be isolated instances of low-level wind shear across North-central, Central, and Southwestern Montana. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 90 55 83 55 / 30 70 30 20 CTB 89 53 80 52 / 20 80 50 50 HLN 85 51 82 53 / 50 70 40 30 BZN 82 46 82 48 / 80 60 40 20 WYS 72 38 79 40 / 70 30 30 10 DLN 75 44 78 46 / 80 20 40 20 HVR 97 59 94 57 / 10 40 20 10 LWT 89 52 84 53 / 10 30 30 10

TFX WATCHES/WARNINGS/ADVISORIES

Heat Advisory from noon today to 9 PM MDT Wednesday for Northern Blaine County.