textproduct: Glasgow

KEY MESSAGES

- An upper low will help bring several rounds of showers and thunderstorms across the area for Sunday. An isolated stronger storm near the MT/ND border remains possible.

- Expect lingering showers early next week with cooler temperatures, but a warm up begins by the middle of the week.

- Another system is expected at the end of the week to bring additional thunderstorms to the region.

DISCUSSION

WEATHER PATTERN OVERVIEW: A weak upper trough is currently overhead. This trough will shift into the eastern part of the area today, and will likely just hang there. The updraft helicity has backed off a bit in the latest HREF, so the activity today will likely remain sub severe. This will keep the showers over the east for most of the day, and then a shortwave trough will push in from the west tomorrow. A weak low level jet is expected to kick in tonight, and with only a small amount of elevated capping overnight in the southern part of the area, a strong thunderstorm or two is possible there. Gusts up to 50 mph and small hail are the main hazards. The cooler surface temperatures will allow the hail to stay together instead of melting right away on its way down to the ground. Daytime heating in the higher terrain of central Montana will bring an opportunity for showers and thunderstorms that have the potential for severe wind gusts and hail after 12 PM Monday. This activity will most likely move out after 9 PM Monday.

The upper trough will slowly break down and move east through Thursday, so a weak ridge will be able to build in. The northeast part of the area will be in the periphery of the trough, so there are still chances for showers and storms through Wednesday afternoon. A larger area of showers and storms is expected to make its way in for Thursday and Friday as the trough starts to rebuild. This is according the latest GFS ensemble.

Ensembles are starting to show the system strengthening by the weekend, so additional shower and thunderstorm chances expected at that time.

FORECAST CONFIDENCE & DEVIATIONS: No deviations from the base forecast.

There is moderate to high confidence in low clouds, showers, and thunderstorms lingering with the upper trough through Monday evening.

There is low to moderate confidence of strong storms occurring in the south tonight, and similar confidence for strong to severe confidence for the afternoon tomorrow across most of the area.

There is moderate to high confidence in showers and storms for Tuesday and Wednesday in the far northeast part of the area, and similar confidence from Thursday onward for the entire area. There is low confidence in severe weather occurring on Friday.

AVIATION

LAST UPDATE: Sunday June 21, 2026 at 1810Z

FLIGHT CAT RANGE: Mostly VFR to MVFR. Isolated IFR.

DISCUSSION: An upper trough pattern is expected to linger through the day tomorrow. This will keep low clouds over the area through this afternoon, and then a break with VFR early tonight, and then low clouds again after midnight. There is low to moderate confidence in IFR conditions occurring in heavy downpours through the afternoon tomorrow, and moderate to high confidence in MVFR conditions occuring in that same timeframe.

WINDS: For KGGW and KOLF, west northwest at 10 to 15 knots, becoming light and variable after 02Z, becoming northwest at 8 to 13 knots after 18Z Monday. For KSDY and KGDV, southeast at 8 to 14 knots, becoming light and variable after 06Z.

GGW WATCHES/WARNINGS/ADVISORIES

None.