textproduct: Great Falls

KEY MESSAGES

- Winter weather and cooler temperatures move into the area today bringing a chance for widespread snow across the region.

- Localized freezing rain and minor ice accumulation possible along the Hi- Line today.

- Generally drier conditions expected Tuesday and Wednesday with some light snow showers possible in the mountains.

- Another round of snow and colder temperatures is possible later in this week into the weekend.

DISCUSSION

/Issued 1205 AM MST Mon Nov 24 2025/

- Meteorological Overview:

A shortwave will move across the area today bringing much cooler temperatures and a chance for widespread snow. Snowfall will begin along the Continental Divide and spread into the island ranges by the late morning and continue into early Tuesday morning. Precipitation along the lower elevations will initially start off as rain and slowly transition to snow as the cold front progresses southward through the afternoon and evening hours. Initial snowfall accumulations will be lost to the warm surfaces but advancing cooler air may allow for some minor accumulations at lower elevations through late Monday night. There will be a concern for freezing rain along portions of the Hi-Line, particularly in Hill and Blaine counties which could cause slick roads today.

Behind the shortwave, transient ridging will briefly keep the area a little drier Tuesday into Wednesday before another shortwave trough is expected to arrive by Thursday. Uncertainty still remains high with how this system will play out but there is a chance for more lower elevation snow and much colder temperatures that follow.

- Forecast Confidence & Scenarios:

Freezing Rain Monday:

The latest HREF shows a greater than 80% probability of at least 0.01" accumulation along and north of US-2. Higher amounts decrease in confidence pretty quickly but there is a 20% chance of isolated freezing rain accumulations up to 0.05". One of the limiting factors for impacts and accumulation will be the road and sidewalk temperatures remain above freezing. But there is still a concern that as temperatures fall to near freezing, any accumulation of freezing rain along area roads will make things slick and become a hazard to motorists.

The main concern will be along elevated surfaces including bridges, power lines, and trees which will run cooler and be more susceptible to accumulating ice. At this time widespread power outages and falling tree limbs are not expected but if the freezing rain event follows through with the higher amounts (closer to 0.05") there may be an isolated power outage in the area.

Accumulating Snow Monday:

Rain showers will start to transition to snow late Monday morning across the lower elevations as the cold front moves down with snow levels expected to fall to around 2,000ft by the late afternoon.

For the most part, significant snowfall accumulation at lower elevations is not expected at this time. Part of this is due to the surface temperatures remaining above freezing leading up to this event which will help to melt some of the first snowflakes. Accumulations up to an inch are possible across the lower elevations through very early Tuesday morning with the potential for some higher amounts along the Canadian border.

Across the northern most portion of the Hi-Line, the HREF has a 40 to 60% chance of 2 or more inches of snow over the period with probabilities dropping to less than 20% along US-2. Given the combined threat of freezing rain with snowfall across the Hi-Line, the current Winter Weather Advisory is sufficient for now as impacts are otherwise expected to remain on the lower end.

As expected the highest snowfall amounts will be found in the mountains. The Northern Rockies along the Continental Divide are expected to see the highest amounts with HREF guidance suggesting a greater than 70% chance for 6 inches or more along Marias Pass through early Tuesday morning. When looking at the probability for exceeding 9 inches of snow, right now any probability above 30% is reserved for the highest elevations well above pass level. So considering these factors, for now, the Winter Weather Advisory will suffice. That being said, there is a concern for brief periods of heavy snow along Marias Pass and should snowfall amounts start to over-perform from the current forecast then a potential upgrade may need to be considered.

Along the Little Belts, there is greater than 80% chance for 6 or more inches at Kings Hill Pass with a 20% chance for 9 inches or more.

Along the Bears Paw, there is a greater than 70% chance for 4 inches or more with some of the higher elevations potentially seeing up to 6-8 inches.

For Bozeman Pass, there is a 50% chance of 2 inches or more with the main concern being the morning commute as there could be a rain/snow mix at pass level which could make things slippery.

Overall, the main concerns through Monday will be travel-related, especially along the mountain passes. Those who venture out should be prepared for sudden changes in road and weather conditions.

Strong Winds Monday:

A period of strong winds is possible, particularly along the Rocky Mountain Front and including MacDonald Pass. Wind gusts up to 55 mph are likely as the front moves through and any shower in the area may help mix down some of those higher wind gusts. When considering the need for a High Wind Warning, the potential window for exceeding high wind criteria is only 1 to 3 hours and confidence in the higher wind gusts occurring is around 30%. So for now there will not be any additional wind headlines issued. But this will be monitored as the winds may over-perform and a short-fused warning may be warranted.

Cooler Pattern Next Weekend:

Overnight temperatures have warmed up a little bit for the weekend into early next week compared to the previous model runs. Single digit to mid teens are still possible for the lows but there is very marginal confidence in some of the coldest ensembles playing out right now. The difficulty in pinpointing exactly how cold it will get is that the final answer will be dependent on how much snow falls across the area. More snow equals colder temperatures. But if this system remains on the drier side then some areas of below zero lows are possible next Sunday and Monday but it will be hard to reach those coldest temperatures without some snow cover to aid it along. -thor

AVIATION

24/12Z TAF Period

An upper level disturbance will move over the Northern Rockies through the day today, with an attendant cold front pushing south from Southern Alberta and across North Central through Southwest Montana between 15-21z Monday. This upper level disturbance will bring low-VFR CIGS to all terminals throughout the duration of the 2412/2512z TAF period, with IFR/MVFR CIGS occurring along and north of a KLWT to KGTF line. Periods of rain/snow will fall throughout the day as the disturbance and cold front move over/across the Northern Rockies, with even a threat for freezing rain/drizzle along and north of the US Hwy 2 corridor prior to 18z this afternoon. Mountains will be obscured for much of the next 24 hours. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 46 21 38 23 / 80 60 0 0 CTB 38 14 33 15 / 90 30 0 0 HLN 41 19 35 22 / 80 40 0 10 BZN 45 15 34 19 / 90 20 0 10 WYS 35 5 29 13 / 90 20 0 20 DLN 43 13 34 21 / 60 0 0 10 HVR 40 17 32 12 / 100 80 0 0 LWT 47 16 34 17 / 80 60 0 0

TFX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 11 PM MST this evening for Big Belt, Bridger and Castle Mountains-East Glacier Park Region- Little Belt and Highwood Mountains-Southern Rocky Mountain Front.

Winter Weather Advisory until 11 PM MST this evening for Bears Paw Mountains and Southern Blaine-Hill County-Northern Blaine County.

Winter Weather Advisory until noon MST today for Eastern Glacier, Western Toole, and Central Pondera-Eastern Toole and Liberty.