textproduct: Great Falls

KEY MESSAGES

Key Points

- Afternoon showers and thunderstorms continue through this evening. - Warming trend through Saturday ahead of a cold front that will bring showers and thunderstorms, some of which may be heavy. - Closer to average to start next week, but afternoon showers and thunderstorms will remain common.

UPDATE

Slight adjustments were made to the short-term forecast based on updated model guidance and trending observations but otherwise no major changes were made. -thor

DISCUSSION

/Issued 556 PM MDT Thu Jun 18 2026/

- Meteorological Overview:

Northwesterly flow aloft continues this afternoon, which is helping to spur the development of pop up afternoon showers and a few rumbles of thunder today. Overall, these showers should not be overly impactful (aside from those caught outside without a raincoat or umbrella) and provide some more beneficial rain, though some small hail cant be entirely ruled out given the cold air aloft.

Once these showers and thunderstorms dissipate this evening, we will have around a 24-36 hour period of dry weather across North Central and Southwestern Montana as a weak transient upper level ridge slides across the area. As it does, temperatures will remain warm across the Southwest Valleys where highs will get to around 80, though the plains will top out around 70.

A cold front will push through the area on Saturday, bringing with it another round of showers and thunderstorms as it pushes through the area. With this forcing mechanism in place, along with some better atmospheric dynamics and more moisture, the showers and storms could be a bit more organized and stronger. Right now, it seems that the largest concern will be some heavy rainfall from the storms, though some gusty winds and hail will also be possible.

Beyond Sunday, northwesterly flow aloft will return to the area for the first half of next week, keeping temperatures closer to average with some afternoon showers and thunderstorms. Another weather system will look to push into the area around midweek, which would bring about another chance for some more organized shower and thunderstorm activity.

- Forecast Confidence & Scenarios:

Showers and thunderstorms today: Overall, showers and thunderstorms this afternoon should remain generally beneficial. However, a few of the stronger thunderstorms may be able to produce some small hail and gusty winds, as temperatures aloft are sufficiently cool to allow for some small hail growth and there is just enough of a dry mixed layer at the surface to promote some modestly gusty outflows to around 40mph or so on the high end.

Saturday Thunderstorms: A cold front moving through the northwestern US on Saturday will bring a round of more organized showers and thunderstorms to the area as it pushes through. While a widespread severe outbreak is not expected at this time, the presence of a forcing mechanism (the front), modest instability, and modest shear profiles indicate there is some potential for the storms to be a bit better organized than those of today and tomorrow. Given this, I cant rule out the possibility of a stronger storm or two that would be able to produce some borderline severe wind or hail (58 mph gusts or 1 inch diameter hail) ahead of the front. The other possibility is that, instead of hail, a few of the storms could produce some heavier downpours, which could produce some minor flooding concerns, particularly in southwestern Montana. Burn scars, such as the Horse Gulch, will be the main concern, but some ponding in low lying areas is also possible. Ludwig

AVIATION

19/00Z TAF Period

Scattered showers and thunderstorms have begun to decrease across central and north-central MT, before dissipating by 03Z. Skies will clear overnight, and winds will turn light and variable around 04Z. -Dzomba

PRELIMINARY POINT TEMPS/POPS

GTF 44 73 48 83 / 20 0 0 10 CTB 40 70 46 79 / 20 0 0 10 HLN 46 78 50 83 / 20 0 0 30 BZN 42 78 47 79 / 0 0 10 60 WYS 36 80 43 72 / 0 0 10 90 DLN 43 81 49 76 / 0 0 10 70 HVR 41 72 48 82 / 20 0 0 0 LWT 39 70 45 77 / 20 0 0 20

TFX WATCHES/WARNINGS/ADVISORIES

None.