textproduct: Great Falls

KEY MESSAGES

- A cold front will bring scattered to numerous showers and thunderstorms today into tonight, with brief downpours, localized gusty winds, and occasional lightning being the primary hazards.

- Cooler temperatures and some showers linger into Saturday and some will see frosty conditions Sunday morning.

- There will be a warming trend Sunday into early next week, with warm, dry, and windy conditions developing ahead of a cold front on Tuesday.

- Cooler conditions and periods of showers and thunderstorms return for the second half of next week.

DISCUSSION

/Issued 253 AM MDT Fri Jun 12 2026/

- Meteorological Overview:

A shortwave trough and attendant cold front will slide southward and bring scattered to numerous showers and thunderstorms today into tonight. Storm activity will initially develop along the Canadian border by the mid- to late morning hours before progressing southward through the plains in the afternoon/evening and eventually into the southwest by tonight. With ML CAPE levels peaking around a few hundred J/kg, gusty winds and brief downpours will be the primary hazards to monitor and this will be mostly be over central and north-central MT.

Another weak shortwave passage will maintain lingering scattered showers and cooler temperatures tonight into Saturday. H700 temperatures falling to the -5 to -8C range may bring some wet high mountain snow tonight into Saturday morning, although this colder air aloft will not be sufficiently phased with the main area of precipitation for any appreciable accumulation.

After a cool, frosty Sunday morning, ridging aloft will initiate a warming trend Sunday through Tuesday. A stronger westerly flow develops ahead of another trough and cold front on Tuesday, along with a stripe of 40 to 50 kt H850/H700 winds. This will bring windy and dry conditions Tuesday afternoon while temperatures surge well into the 80s. The cold front will pass through sometime Tuesday night into Wednesday and will reintroduce scattered shower and thunderstorm activity and cooling temperatures for the second half of the week. - RCG

- Forecast Confidence & Scenarios:

Scattered to numerous showers/thunderstorms and cooling temperatures today through early Sunday...

The primary impact from today's general thunderstorm risk will be for unfavorable conditions for outdoor recreation. Localized downpours, gusty winds, and occasional lightning will become more prevalent over central and north-central MT as the day progresses. The cold front will also bring a gusty and chilly northerly wind shift with most plains locations seeing their high temperatures peak in mid- morning through the early afternoon hours, earliest along the Hi-Line.

This activity will become more scattered in nature as it moves into southwest MT later this evening into tonight. Then a secondary shortwave will maintain at least isolated shower activity through Saturday. The nights will be on the chillier side as well, especially Sunday morning when most lower elevations will see lows in the lower to middle 30s and scattered areas of frost. The wind protected southwest valleys will see the coldest conditions.

Warm, windy, and, dry Tuesday...

Westerly winds begin to increase on Tuesday in advance of an approaching through and cold front. The NAEFS anomaly index already has H700/H500 winds approaching two to three standard deviations above climatology with NBM probabilities for 50 mph + gusts already running above 50% for portions of the forecast area, including the Rocky Mountain Front/plains west of I15 and areas over and near the higher terrain of central/southwest MT. The biggest uncertainty will be when the strongest winds aloft move through and whether it will be during peak diurnal mixing or later in the evening with less momentum transfer.

With this event being four to five days out, there's plenty of time to iron out any changes in trough/jet streak timing and positioning. At this time, the primary impact looks be inclement outdoor recreation and difficult travel for those operating high profile vehicles. The combination of temperatures warming well into the 80s and RHs falling to near critically low levels will also be monitored for fire weather concerns, although fuels will be less receptive given recent rainfall and greenup. - RCG

AVIATION

12/12Z TAF Period

A cold front will bring scattered to numerous showers and thunderstorms and a northerly wind shift to the plains later this morning and into the afternoon before moving into the southwest this evening and tonight. Low VFR/MVFR clouds and mountain obscuration will increase from north to south. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 68 43 62 39 / 70 80 10 0 CTB 59 38 61 36 / 80 30 0 0 HLN 73 44 63 40 / 40 60 20 0 BZN 73 41 62 36 / 10 50 30 0 WYS 69 34 62 30 / 10 10 0 0 DLN 75 40 64 36 / 0 0 0 0 HVR 64 40 66 39 / 60 10 0 0 LWT 65 39 57 36 / 40 50 30 0

TFX WATCHES/WARNINGS/ADVISORIES

None.