textproduct: Great Falls

KEY MESSAGES

- Cooler temperatures and widely scattered showers linger today, with cool and frosty conditions for some areas Sunday morning.

- A warming trend begins on Sunday and continues through early next week, with windy conditions developing ahead of a cold front on Tuesday.

- There will be a period of showers and thunderstorms and more gusty winds with the frontal passage late Tuesday into Wednesday.

- General unsettled conditions continue for the for the second half of next week with more opportunities for showers and storms.

DISCUSSION

/Issued 307 AM MDT Sat Jun 13 2026/

- Meteorological Overview:

Northwesterly flow aloft will remain in place through at least the latter part of the workweek. Lingering showers from last night continue to thin out as they move southward into southwest MT. Another shortwave will bring another round of showers and perhaps a storm or two this afternoon and evening, although this activity looks to be more scattered in nature and mostly developing over and near areas of higher terrain, especially the central island ranges.

After a cool, frosty Sunday morning, the eastern periphery of a Pacific NW Ridge will will move into the Northern Rockies and initiate an early week warming trend. Westerly flow aloft increases late Monday into Tuesday in advance of an approaching shortwave and attendant cold front with H850/H700 winds increasing to the 40 to 50 kt range by Tuesday evening. This will bring windy and dry conditions Tuesday afternoon while temperatures surge well into the 80s.

A Canadian cold front will move southward sometime late Tuesday into Wednesday and bring a round of showers and thunderstorms. Temperatures fall below average behind the front Wednesday and Thursday while gusty northwesterly winds continue through Wednesday afternoon, strongest for central/north-central locations east of I15. Passing shortwaves bring more rounds of showers and thunderstorms heading into the first half of next weekend. - RCG

- Forecast Confidence & Scenarios:

Chilly/frosty overnight and morning temperatures...

Partial clearing and light winds will result in chilly low temperatures for the next couple of nights, especially tonight into Sunday morning. Most lower elevations will see morning lows in the 30s, along with some instances of patchy frost. The wind protected southwest valleys will see the coldest conditions and most widespread frost.

Windy conditions Tuesday into Wednesday...

Westerly winds increase on Tuesday in advance of an approaching through and cold front. The NAEFS anomaly index continues to advertise H700/H500 winds increasing up to two to three standard deviations above climatology and NBM probabilities for 50 mph + gusts are now running in the 60 to 80% range 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 continues to 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. Another factor that may slow wind speeds and reduce the duration of peak winds will be an early arrival of the Canadian cold front. The timing of this front will affect northern areas the most, particularly areas along the Northern Rocky Mountain Front.

The winds will shift to a more northwesterly direction on Wednesday and will generally be strongest over the plains east of I15, namely southeastern Blaine and Fergus counties. With this event still days away, there's time to iron out these details. 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 on Tuesday will also be monitored for fire weather concerns, although fuels will be less receptive given the recent rainfall and greenup. - RCG

AVIATION

13/12Z TAF Period

Shortwave energy moving within a northwesterly flow aloft will maintain scattered to broken low VFR/MVFR clouds and a few widely scattered showers through around 14/00Z. Surface winds will generally be north to northwest with wind speeds mostly remaining below 25 kts. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 62 40 70 44 / 20 0 0 0 CTB 61 37 71 44 / 10 0 0 0 HLN 63 40 73 44 / 30 0 0 0 BZN 62 35 70 39 / 40 10 0 0 WYS 63 30 69 32 / 10 10 0 0 DLN 64 36 70 40 / 20 0 0 0 HVR 67 40 73 45 / 10 0 0 0 LWT 57 37 67 40 / 30 10 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.