textproduct: Great Falls

KEY MESSAGES

- Daily chances for showers and thunderstorms start out in Southwest MT early this week with it shifting northwards Thursday.

- Temperatures gradually warm through Thursday.

- Cooler and breezier conditions move in for the weekend.

DISCUSSION

/Issued 213 PM MDT Mon Aug 24 2026/

- Meteorological Overview:

Upper-level ridging will help keep most of the region dry through Wednesday. The main exception being Southwest MT, where a slow return of monsoonal moisture with mini vorticity maximums will allow for isolated showers and thunderstorms to develop. Today, precipitation is more focused towards the MT/ID border, and tomorrow/Wednesday is focused along and south of I-90. Although there will be enough moisture for convection through Wednesday, a very dry surface layer will bring isolated dry thunderstorms. Deep inverted V sounding profiles will also bring an isolated strong wind threat to convection (low confidence in severe wind gusts). Coverage in showers and thunderstorms increase northwards throughout the week, becoming widespread across the region on Thursday. A trough coming onshore Thursday through the weekend will increase winds aloft and keep daily precipitation chances across the region. Better forcing and shear Thursday signals a potential threat for isolated strong to severe wind gusts, mainly in the mountain valleys/foothills of the Continental Divide. Temperatures gradually warm throughout the week with increasing southwest flow aloft.

During the weekend, the trough axis moves across the region. This brings a better synoptic setup for widespread precipitation on Sunday. How much precipitation and where the better corridor of precipitation set up depends on the evolution of this upper-level wave (a compact closed low vs a broader wave/trough). This trough will bring cooler temperatures to the region for next week along with widespread breezy winds for the weekend (with uncertainty how windy it gets based on the trough evolution). -Wilson

AVIATION

25/00Z TAF Period

The main concern through the first 6 hours of the period will be impacts to slantwise visibility as a result of wildfire smoke. The most likely to see impacts will be KGTF, KLWT, KHLN, and KBZN. While surface visibility impacts are not expected at this time there will be a concern for mountain obscuration through at least 25/09Z with some areas closer to the fires along the divide and Southwest Montana expected to experience greater impacts.

Thunderstorm activity along the Montana/Idaho border is expected to remain isolated in nature. There are minimal concerns for impacts to the terminals at this time but should a thunderstorm develop nearby the main concerns would be lightning and gusty/erratic winds. There is a chance for another round of isolated thunderstorms in Southwest Montana on Tuesday with around a 30% chance for impacts in the vicinity of KBZN and KWYS.

For KGTF: Aside from the smoke, there are no concerns this TAF period. Outside of an occasional gust up to 10kts this afternoon, winds will remain light through the overnight hours. Winds will start to pick up out of the northeast Tuesday afternoon but confidence in a strong crosswind is less than 20% at this time. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 52 82 54 89 / 0 0 0 0 CTB 48 77 50 85 / 0 0 0 0 HLN 53 84 54 89 / 0 10 10 0 BZN 49 83 51 87 / 0 0 40 10 WYS 41 79 41 81 / 20 30 30 10 DLN 49 84 50 86 / 0 30 20 20 HVR 51 82 52 91 / 0 0 0 0 LWT 48 80 50 87 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.