textproduct: Great Falls

KEY MESSAGES

- Isolated fog possible Sunday morning.

- Cooler temperatures and dry conditions persist through the weekend.

- Another period of unsettled weather moves in late Monday through next weekend.

DISCUSSION

/Issued 139 PM MDT Sat Oct 24 2026/

- Meteorological Overview:

Weak zonal flow aloft with high pressure will continue to dominate the weather pattern through Sunday. This continues to bring benign conditions today and Sunday, with calmer winds and cooler temperatures. With recent the snowfall and some melting snow today, there will be lingering low level moisture across the region. Another morning of calm winds and high pressure can develop fog and/or low stratus clouds across the region Sunday morning.

Monday, a closed upper-level low moves onshore of the Pacific Northwest, with the wave opening back up as it propagates east. This next incoming system brings snow to the higher elevations and rain/snow to the lower elevations. There remains some uncertainty in how much cold air aloft this system brings, but low temperatures Tuesday morning below freezing can allow for light snow to mix down to lower elevations.

Ensembles hint at an unsettled, cooler pattern sticking around through next weekend as a continuous line of shortwave trough move across the Northwest U.S. Generally the pattern shows mountain snow with rain at lower elevations during the day, and light snow at night.

- Forecast Confidence & Scenarios:

Fog Sunday morning:

Both forecast soundings and probabilistic guidance supports the potential for fog and stratus developing for isolated portions of the region, with highest chances in Cascade and Lewis & Clark Counties. Here, there's a 20-60% chance for fog development, with a 20-30% chance for fog dropping visibility to below a mile. One caveat is there is also a 20-60% chance for low stratus to develop, which may limit overall fog development.

Storm System Early Next Week:

Ensembles don't hint at this system being a big snow producer for either the mountains or lower elevations. This system tries to pull in colder air aloft, but it's not very rigorous. Snow levels try to fall to the lower elevations overnight Monday into Tuesday morning, which will allow for some snow to reach the lower elevations. However, current trends have the wet bulb temperatures rise above freezing, limiting overall impacts at lower elevations. -Wilson

AVIATION

25/00Z TAF Period

The primary concern this TAF period will be for fog and low clouds through Sunday morning across most terminals. Areas of greatest concern are across SW MT valleys and portions of Central MT. Confidence in dense fog was too low to include mention in any TAF at this time. Mountains will become increasingly obscured heading into Sunday morning. -AM

PRELIMINARY POINT TEMPS/POPS

GTF 24 38 22 41 / 0 0 0 0 CTB 22 41 20 43 / 0 0 0 0 HLN 23 38 22 46 / 0 0 0 0 BZN 20 45 18 50 / 0 0 0 0 WYS 15 51 17 48 / 0 0 0 0 DLN 24 43 25 51 / 0 0 0 0 HVR 21 46 22 50 / 0 0 0 0 LWT 20 40 23 48 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.