textproduct: Great Falls

KEY MESSAGES

- Areas of dense fog this morning will improve some this afternoon but is likely to redevelop tonight and potentially again Friday night.

- Seasonable afternoon temperatures the next few days, with the potential for warmer afternoon temperatures by later next week.

- A good chance for widespread rain and snow Saturday night into Sunday over much of the region.

UPDATE

Areas of fog and low clouds persist across much of the north-central MT plains this morning, where a very moist low level airmass is in place on the southwestern fridge of surface high pressure centered across the Canadian Prairies. Light low level easterly upslope flow is supporting some of the most widespread/dense fog affecting areas adjacent to the Rocky Mountain Front and east across Cascade county into portions of Fergus county. A Dense Fog Advisory continues through the rest of this morning with some improvement expected to visibility this afternoon, but areas of low clouds are likely to linger, particularly adjacent to the Rocky Mtn Front.

Tonight through Friday night...Surface high pressure currently centered across southern AB/SK slowly slides eastward through Friday night and is likely to hold the shallow/moist airmass in place across the the plains, maintaining at least some areas of low clouds and fog across portions of north-central MT. Dense fog advisories will likely be needed again tonight through Friday morning for many of the same locations experiencing fog this morning. Latest high resolution model ensembles give a 60% probability for visibility 1/2 mile or less for areas of north-central MT along and west of I-15. Additionally, overnight temperatures near or slightly below freezing will support freezing fog again tonight as well, and even the potential for some patchy freezing drizzle with the risk for localized icing, particularly affecting bridges and overpasses.

Looking ahead to the weekend...latest model guidance continues to support widespread precipitation development Saturday night into Sunday with precipitation exiting the area Sunday night or Monday morning. There is a trend toward slightly higher snow levels and slower lowering of snow levels Sunday. The keeps the focus for minor winter weather impacts mainly across the higher elevations of southwest MT. Hoenisch

DISCUSSION

/Issued 346 AM MDT Thu Oct 29 2026/

- Meteorological Overview: A slightly southwesterly flow aloft is over MT, as an upper level disturbance is moving northeast from Glacier Park up into southern Canada. Expect light snow this morning along the divide to become more scattered later today. Some partial clearing overnight has allowed dense fog to develop over portions of North Central MT early this morning.

For Friday into Saturday, weak upper level ridging is forecast to develop over the CWA, along with seasonable temperatures.

For Saturday night through Sunday night...an upper level low over the Pacific Northwest will move southeast towards Utah. This will result in a moist southerly flow aloft to develop over Central MT. As a result, rain/snow is expected to develop Saturday night over Southwest MT and then move into Central MT by Sunday morning.

The precipitation will exit the area on Monday, as the next upper level ridge starts to build over the northern Rockies. The main question with this next upper level ridge is how strong will it be? Overall, do expect drier and slight warmer conditions by the later portions of next week as this upper level ridge develops.

- Forecast Confidence & Scenarios: The winter weather advisory for the Rocky Mountain will likely be cancelled by 6 AM, as snow is expected to lighter and begin to diminish between 6 AM and Noon in that region.

The dense fog advisory will continue through this morning. There is the potential the dense fog advisory could be extended, as the fog will be slow to burn off.

The storm system this weekend will bring rain/snow to much of the CWA. Snow levels will be high to start, generally above 7000 feet on Saturday, but then are forecast to fall down to about 4000 feet by Monday. By Monday, most of the precipitation will have exited the region, but mountain snowfall is likely Saturday night into Sunday. Snow accumulations around the Pony/Big Sky area are starting to approach warning criteria. Thus a winter storm watch might be needed for Zone 330. Otherwise, a winter weather advisory is looking likely for mountain areas of Southwest and portions of Central MT from Saturday night into Sunday night.

Looking ahead to the middle of next week, if the upper level ridge develops and is a bit stronger than currently forecast, afternoon temperatures might be a bit warmer than currently forecast for the later half of next week. Brusda

AVIATION

29/12Z TAF Period

Main concern this morning will be the areas of dense freezing fog over portions of North Central MT. Visibility is down to a 1/4SM at times in the dense freezing fog. Overall, the fog will likely be slow to burn off with light winds today, along with some high clouds moving over the top of the fog this morning. Light snow showers are expected along the divide this morning, before decreasing this afternoon. Mountains/passes will be obscured into the afternoon hours by clouds/precip. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 41 29 41 28 / 0 10 0 0 CTB 35 25 36 25 / 10 30 10 0 HLN 49 28 47 30 / 0 0 0 10 BZN 48 26 47 30 / 0 0 0 0 WYS 45 22 49 25 / 0 0 10 40 DLN 45 28 48 31 / 0 0 10 10 HVR 41 23 44 25 / 0 0 0 0 LWT 46 24 46 28 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until noon MDT today for Cascade County below 5000ft-Eastern Glacier, Western Toole, and Central Pondera- Eastern Pondera and Eastern Teton-Eastern Toole and Liberty- Fergus County below 4500ft-Gates of the Mountains-Judith Basin County and Judith Gap-Northern High Plains-Southern High Plains.