textproduct: Great Falls

KEY MESSAGES

- Brief warm up today with generally dry conditions expected across the region.

- Warm start to Saturday before a cold front arrives and brings a chance for afternoon showers and thunderstorms, some of which may be heavy.

- More seasonable temperatures remain through the start of next week with daily chances for showers and afternoon thunderstorms.

DISCUSSION

/Issued 1201 AM MDT Fri Jun 19 2026/

- Meteorological Overview:

Brief transient ridging will move across the region Friday allowing for temperatures to briefly warm up into 70s across the Northern Plains and up into the low 80s for some portions of Southwest Montana.

On Saturday, a combination of monsoonal moisture pushing into Southwest Montana and a cold front dipping down from Canada will bring a chance for afternoon showers and thunderstorms across the region. Showers and thunderstorms are expected to initially develop in the early afternoon across Southwest Montana and become more widespread into Central Montana by the mid-afternoon. The main concern with any thunderstorm that develops will be strong, gusty winds and hail. For Southwest Montana in particular there is an additional concern for localized flooding.

Starting Sunday through Tuesday, northwesterly flow returns to the region bringing more seasonable temperatures to the region and daily chances for showers and afternoon thunderstorms. For Wednesday through the end of the work week, upper-level ridging starts to build back across the western CONUS which will allow for warmer temperatures to return to Montana.

- Forecast Confidence & Scenarios:

Not too much has changed in the overall picture for Saturday. Modest instability and shear are still in place through the afternoon hours and the chance for scattered the widespread showers and thunderstorms lasting through the evening is still relatively high.

When it comes to shear, North-Central Montana including the Hi-Line has the best values ranging from 20-35kts through the afternoon hours. Combined with modest CAPE values there is a potential that a couple thunderstorms could turn severe. Although the threat will remain quite localized and no widespread severe weather is expected across the region. The main concerns for North-Central Montana, especially across the Hi-Line will be strong, gusty winds.

As for Southwest and Central Montana, Southwest Montana is comparatively lacking in shear, which could lead to slower storm motion, and Central Montana is a bit of a transition zone with some pockets of higher shear possible but overall still less than what is currently modeled along the Hi-Line. With similar CAPE values the difference will be there is a higher chance for hail in this portion of our CWA. But there is an equally likely possibility that most of the hail might melt on its way down with the result being localized heavy downpours. Model soundings continue to show and environment that is ripe for heavy rain across Central and Southwest Montana. Thus, while strong winds and hail are definitely something to watch for through the evening hours, the bigger concern will be localized ponding or flooding, especially in typically flood-prone areas. This includes the Horse Gulch burn scar which will be closely monitored throughout the afternoon and evening hours as, depending on how slow the thunderstorms move, rainfall rates could cause some flooding in the nearby campground areas.

The main message to those recreating outdoors will be to check in with the latest forecast before heading out, have a way to receive warnings in case the situation deteriorates quickly, and be prepared to seek higher ground away from floodwaters in the event of flash flooding. -thor

AVIATION

19/12Z TAF Period

VFR conditions are expected to prevail across all terminals through the 1912/2012 TAF period; however, an isolated shower or storm can't be ruled out over the higher terrain of Southwest Montana between 21z this afternoon and 03z this evening. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 73 48 82 51 / 0 0 10 30 CTB 70 45 80 46 / 0 0 10 10 HLN 78 50 83 52 / 0 0 20 20 BZN 78 47 79 48 / 0 0 50 50 WYS 80 43 70 39 / 0 0 70 70 DLN 81 49 76 46 / 0 0 60 50 HVR 72 48 82 50 / 0 0 0 50 LWT 70 45 77 48 / 0 0 10 30

TFX WATCHES/WARNINGS/ADVISORIES

None.