textproduct: Great Falls

KEY MESSAGES

- Thunderstorms across southwest Montana and eastern portions of central Montana through this evening may produce locally strong wind gusts.

- Daily thunderstorm activity is expected through Wednesday with a risk of locally heavy rainfall accompanying some storms late Monday and Monday night and a few strong to severe storms on Wednesday.

- Seasonable temperatures this week will likely warm well above average for the upcoming weekend.

DISCUSSION

/Issued 150 PM MDT Sun Jul 5 2026/

An active summer weather pattern is in place through Wednesday as the area remains on the periphery of a building upper level ridge across the central/southern Rockies while upper troughing sends shortwave energy across southern BC/AB today and again Wednesday. In between these waves, a disturbance with sub-topical moisture connections circulating to the west of the ridge lifts north from the Great Basin across the area late Monday/Monday night.

Thunderstorm development is beginning early this afternoon across SW MT within a stalled lower to mid-level baroclinic/convergence zone. Expect storms to track northeast through a corridor from SW MT this afternoon and across eastern portions of central MT (JB/Fergus counties) this evening. Steep mid-level lapse rates, modest CAPE (up to around 1500 J/kg) and sufficient wind shear will support some organized/stronger storms late this afternoon with a deeply mixed boundary layer conducive to strong wind gusts as the primary thunderstorm hazard, though a few storms could also produce small hail. As these storms exit/diminish late this evening a cooler airmass will surge south from AB behind the departing shortwave, bringing a wind shift and period of gusty north winds after its passage during the overngiht period. Cooling will be most noticeable across north-central MT where where afternoon temps will be around 10-15 degrees cooler than today (lower to mid 70s), while SW MT sees less pronounced cooling of around 5-10 degrees from today.

The disturbance rotating around the back side of the ridge will spread showers and thunderstorms into SW MT late Monday afternoon. Lower level instability may be hindered by mid-high cloud-cover in advance of the wave Monday afternoon but elevated/mid-level instability and deeper moisture associated with the wave should support a fairly widespread coverage of showers and thunderstorms that persist through Monday night as the wave lifts through the area. While buoyancy/CAPE and shear is somewhat limited for organized storms, deep moisture (PWATS >150% climo), relatively slow steering winds and the presence of a mid level vort feature does maintain some concern for instances of localized heavy rainfall, especially near more sensitive terrain locations.

A relatively moist airmass in the wake of the Monday night disturbance will be in place for afternoon heating/destabilization to produce isolated/scattered thunderstorms again Tuesday afternoon. This airmass will remain across the the area into Wednesday, setting the stage for thunderstorm development with the arrival of the next Pacific wave/trough tracking east across AB/SK late Wednesday. Models continue to depict sufficient CAPE and shear to support potential strong to severe thunderstorms Wednesday afternoon/evening.

Upper level ridging centered south of the area amplifies later this week through the upcoming weekend pushing temperatures 10-15 degrees above average by the weekend. The risk of showers and thunderstorms decreases significantly beginning Thursday. Hoenisch

AVIATION

06/00Z TAF Period

Initial concern this TAF period will be for showers and thunderstorms across portions of Southwest through Central Montana which will be capable of producing gusty and erratic winds along with hail. These thunderstorms move out by 06Z or so but in the meantime a boundary dropping south from Canada will result in a gusty wind shift over the plains this evening and early overnight. Low clouds look to accompany this wind shift, though there is uncertainty as to how long these lower clouds linger into Monday morning. Another round of showers and thunderstorms develops through the day Monday, again capable of gusty and erratic winds and hail. -AM

PRELIMINARY POINT TEMPS/POPS

GTF 53 76 55 82 / 0 20 60 20 CTB 47 74 53 81 / 0 0 40 10 HLN 55 78 56 85 / 20 30 80 10 BZN 54 81 52 82 / 20 30 70 20 WYS 48 80 47 78 / 20 20 40 20 DLN 53 78 50 81 / 10 40 50 20 HVR 52 81 57 79 / 0 0 60 60 LWT 50 75 51 76 / 70 10 80 60

TFX WATCHES/WARNINGS/ADVISORIES

None.