textproduct: Great Falls

KEY MESSAGES

- Temperatures well below normal over the plains of Central and North Central Montana on Friday, with above normal highs in the valleys of Southwest Montana.

- Moderate to heavy snow develops overnight tonight and through the day on Friday over Central and North Central, especially east of the I-15 corridor.

- Several days of windy conditions are expected next week over North Central MT.

UPDATE

/Issued 733 PM MST Thu Dec 11 2025/

Snowfall bands have begun to develop across North Central Montana, with the most prominent one currently south of Great Falls, though there are some additional convective type snow showers along the Montana Hi-Line this evening. Further south, subfreezing temperatures have settled into the Helena Valley, though warmer air remains aloft. A few rain showers may survive the trek across the Continental Divide and produce some rain showers in the valley, which may freeze to trees, bridges, and overpasses, but ground temperatures should remain above freezing long enough to prevent widespread accretions of ice on roads and sidewalks. As such, I have addressed this with a Special Weather Statement instead of issuing a Winter Weather Advisory at this time, but will continue to evaluate the situation through the evening. Ludwig

DISCUSSION

/Issued 733 PM MST Thu Dec 11 2025/

- Meteorological Overview:

The Arctic front, which surged south across the plains of North Central and Central Montana between 15-18z this morning, will continue to progress (albeit slower and modified with respect to temperatures) south towards the US Hwy 12 corridor in Central Montana through the remainder of the afternoon and early evening hours before stalling. Strong low level frontogenesis associated with this front combined with Pacific moisture overrunning the Arctic airmass was helping to support scattered bands of precipitation largely in the form of snow over the plains and mountains of North Central and Central Montana; however, brief periods of rain or freezing rain were occurring along the immediate frontal boundary. This freezing rain threat will gradually subside through the remainder of the afternoon hours as temperatures aloft cool and the Arctic airmass deepens.

As the best forcing shifts south with the front precipitation will temporary end from north to south through the afternoon hours today, with most of precipitation being focused south of the Montana Hwy 200 corridor and north of the US Hwy 12 corridor through the evening hours tonight. By the late evening hours tonight a mid-level warm front will then begin to lift north to northeast over the Arctic airmass that is in place. This northward progression of the mid- level warm front will help to reorient the band of snow across Central Montana back to the north and over North Central Montana in northwest to southeast orientation through the day on Friday. The northward progression (i.e. speed) of this mid-level warm front will strongly dictate how much snow eventually falls across portions of Central and North Central Montana (i.e. slower progression will allow for more snow while a faster progression will lead to less snow), especially along and west of the I-15 corridor to the Rocky Mountain Front where low-level drying due westerly flow aloft will be occurring. Snow will gradually end from southwest to northeast from the late afternoon/early evening (Central Montana) hours on Friday to the early morning hours on Saturday (North Central Montana). - Moldan

- Forecast Confidence & Scenarios:

Accumulating Snow through Friday/Friday night...

High End Snowfall (10% chance of occurring) : A slower moving mid- level warm front helps to support a prolonged period of moderate to heavy snow across all of the plains of Central and North Central Montana, with snowfall amounts approaching 12" over the plains of Central and North Central Montana east of the I-15 corridor and 12- 20" in the mountains of Central and North Central Montana.

Low End Snowfall (10% chance of occurring) : A faster moving mid- level warm front limits the time for moderate to heavy snow, especially along the I-15 corridor where downsloping westerly winds lead to snow accumulation of generally less than 1". Across the remainder of the plains to the east snowfall accumulations generally range from 2-5", with 5-10" in the mountains. - Moldan

Strong winds early next week...There is already and 80 percent chance that winds could exceed warning criteria along the Rocky Mountain Front and in the Cut Bank area Mon and Tue and a 60 percent chance on Wed. Brusda

AVIATION

12/06Z TAF Period

The shallow leading edge of a deeper cold airmass in place across the north-central MT plains has pushed as far south as Toston with colder air potentially trickling into the Gallatin valley and KBZN by early Friday morning. MVFR conditions are widespread across area TAF sites with IFR conditions becoming more likely later tonight through Friday morning across N-central MT as a steadier area of widespread precipitation lifts north and intensifies. While precipitation type is primarily snow across north-central MT, freezing rain is occurring in KHLN and likely to persist into Friday morning with lower confidence in potential for -FZRA at KBZN . Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 56 2 11 5 / 80 80 90 50 CTB 51 -4 4 -2 / 40 50 90 90 HLN 57 21 34 26 / 80 90 80 10 BZN 59 33 45 33 / 50 80 70 10 WYS 41 29 37 21 / 30 50 50 10 DLN 57 41 51 33 / 10 10 10 0 HVR 39 -7 0 -8 / 70 60 90 100 LWT 49 5 10 4 / 100 100 100 70

TFX WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory until 10 AM MST Friday for Eastern Glacier, Western Toole, and Central Pondera-Eastern Toole and Liberty-Hill County-Northern Blaine County.

Winter Storm Warning until 5 AM MST Saturday for Fergus County below 4500ft-Judith Basin County and Judith Gap.

Winter Weather Advisory from 4 AM Friday to 5 AM MST Saturday for Eastern Glacier, Western Toole, and Central Pondera-Eastern Pondera and Eastern Teton-Northern High Plains.

Winter Storm Warning from 4 AM Friday to 5 AM MST Saturday for Bears Paw Mountains and Southern Blaine-Eastern Toole and Liberty-Hill County-Northern Blaine County-Western and Central Chouteau County.

Winter Storm Warning until 6 PM MST Friday for East Glacier Park Region-Little Belt and Highwood Mountains-Snowy and Judith Mountains-Southern Rocky Mountain Front.

Winter Weather Advisory until midnight MST tonight for Fergus County below 4500ft-Judith Basin County and Judith Gap-Little Belt and Highwood Mountains-Snowy and Judith Mountains-Southern Rocky Mountain Front.

Winter Weather Advisory until 6 PM MST Friday for Big Belt, Bridger and Castle Mountains-Cascade County below 5000ft-Gates of the Mountains-Meagher County Valleys-Southern High Plains- Upper Blackfoot and MacDonald Pass.

Winter Weather Advisory until midnight MST Friday night for Helena Valley.