textproduct: Great Falls

KEY MESSAGES

- Scattered showers and isolated thunderstorms develop mainly along and east of I-15 this afternoon.

- Another round of scattered to widespread showers with isolated thunderstorms expected on Sunday.

- Breezy winds develop this weekend, especially in Southwest MT.

- An active, cooler weather pattern is on tap Tuesday through the work week.

DISCUSSION

/Issued 1217 AM MDT Sat Jun 6 2026/

- Meteorological Overview:

Southwest flow aloft today will continue to advect in moisture and vorticity maximums across the region. This will bring in scattered showers with isolated thunderstorms mostly along and east of I-15 this afternoon. However, there will be some rain this morning along the Rocky Mountain Front. With the stationary front through Southwest/Central MT already, the thunderstorm threat will most likely be off to the east. Mid level winds increases throughout the afternoon, which will bring windy conditions to Southwest MT.

On Sunday, the main trough axis moves through the region. A cold front passage Sunday will bring better chances for scattered to widespread precipitation during the day. Weak instability will allow for some thunderstorms to develop, mainly towards Central MT. Snow levels falling to 6,000 to 7,000ft Sunday morning along the southern Continental Divide and down to 5,500ft towards the northern Continental Divide will allow for light mountain snow to develop. Below normal temperatures are expected Sunday. Stronger flow aloft with the trough passing through will slow bring another breezy to windy day, especially across Southwest MT.

With this trough exiting the region, Monday will be a drier day overall. Though Southwesterly flow aloft will continue to bring a low end chance for light showers during the day and breezy winds. The main closed 500mb low moves onshore Tuesday, and slowly make it's way east through eh week. This will bring another active, cooler pattern for the week. There are some differences in models with the amplitude and timing of this next trough, which will bring subtle differences in precipitation amounts. However, ensembles are in agreement for a wetter cooler pattern through at least next Friday.

- Forecast Confidence & Scenarios:

Weekend Thunderstorm Risk:

Generally, instability isn't really robust for thunderstorm development today. Also, the main synoptic low being in the eastern part of MT doesn't help place us in the best sector for warm and unstable air. However, with winds aloft increasing in the afternoon, I can't rule out a few strong winds with thunderstorms in Southwest and Central MT.

The main limiting factor Sunday is the timing of the cold front. The cold front is already reaching Fergus and Blaine County by 12pm, which does not support robust surface heating for thunderstorms. A little slower in the time of precipitation will increase the risk for stronger storms. With PWATs decreasing throughout the day, the heavy rainfall threat with storms are low.

Lowering snowfall levels Sunday will allow for light snow to develop, but light accumulations look to remain above pass level.

Winds This Weekend:

The pressure gradient front and increase in winds aloft will keep windy conditions to Southwest MT Saturday and Sunday. The highest impacts will be across the higher terrain, with only up to a 30% for 50 mph wind gusts in the valleys near the MT/ID border. However, showers could bring down some 50-55mph wind gusts to the surface. Sunday's winds will be slightly higher, with up to a 50% chance for 50 mph wind gusts in those valleys. -Wilson

AVIATION

06/12Z TAF Period

Mid-high level cloud-cover increases today as additional moisture moves through a southwesterly flow aloft. VFR conditions prevail with just a few light/high-based showers tracking across the region this morning. Showers and thunderstorms increase this afternoon and track north-northeast through this evening with some risk for locally strong wind gusts and brief MVFR conditions. Surface winds remain somewhat variable across north-central MT this morning with a shift to north/northwest winds and increase in wind speed this evening. Gusty south/southwest winds develop again by this afternoon across SW MT terminals with a shift to northwest winds occurring Saturday evening. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 72 45 57 40 / 30 50 70 10 CTB 65 40 57 38 / 20 10 20 0 HLN 74 45 58 37 / 40 50 80 10 BZN 80 43 61 32 / 20 50 90 30 WYS 77 40 62 27 / 10 30 20 0 DLN 78 43 60 33 / 20 20 50 10 HVR 76 45 63 40 / 20 60 50 20 LWT 77 42 57 36 / 30 60 90 30

TFX WATCHES/WARNINGS/ADVISORIES

None.