textproduct: Great Falls

KEY MESSAGES

- Heavy snow will continue across portions of north-central and central Montana through the night.

- Light mixed precipitation and freezing rain is possible across portions central Montana through tonight with accumulations up to a light glaze possible.

- A cold airmass remains over the plains through Saturday before windier and warmer conditions develop late this weekend into early next week.

UPDATE

/Issued 837 PM MST Fri Dec 12 2025/

The band of snow that has persisted across the area this evening has been slowly drifting northeastward over the past few hours and weakening slightly. Expect this weakening trend to continue overnight even as it sags back southward late tonight and early tomorrow morning before dissipating early Saturday. With this in mind, I have trimmed the Winter Weather Advisories and Winter Storm Warnings a bit to reflect this. Ludwig

DISCUSSION

/Issued 837 PM MST Fri Dec 12 2025/

- Meteorological Overview:

A band of moderate to heavy snow will persist over portions of north-central and central Montana through the overnight hours bringing locally heavy snow and moderate to heavy snowfall rates. Impacts to travel and infrastructure are possible and those heading out should be prepared for rapidly deteriorating road and weather conditions.

Along the fringes of precipitation there is a concern for light freezing rain across portions of central Montana where accumulation up to a light glaze is possible. Travel may become hazardous for much of the region through the overnight hours.

Overnight lows from 15 below to 10 above are expected across the plains of north-central Montana this evening while the valleys of central and southwest Montana will remain closer to freezing. Through the weekend the upper level ridge will shift slightly eastward which will help to push out the colder airmass and allow for warmer and windier conditions to return to the region through at least

- Forecast Confidence & Scenarios:

Heavy Snow Continues Across North-Central Montana:

The snowband is fully underway across portions of north-central and central Montana this afternoon with the heaviest snow roughly stretching from the Chester/Inverness area down to Custer. As the evening progresses this band is expected to slowly march to the northeast with the axis of heaviest snow resting on a line between Havre and Terry. An additional 4 to 6 inches is possible across the lower elevations of Hill, Blaine, and northern Fergus counties with up to 10 inches possible in the Bears Paw. Locally higher amounts are possible under heavier portions of the snowband.

As it has been stated in previous messaging, there may be a sharp snowfall accumulation gradient as a result of the snowband where locations directly under the snowband may receive the full forecasted amount, and potentially more, while locations just outside the snowband may experience much less snowfall.

The main concern will be slippery roads and reduced visibility due to heavy snowfall rates and the potential for blowing snow across the Hi-Line. Additionally, periods of blowing snow may lead to some patchy snow drifts along area roads including Highway 2 and Highway 66 which may make travel difficult at times.

This snowband will slowly start to taper off early Saturday morning and the heaviest snow is expected to end by around 4 to 6 AM. Light snow showers may linger in the area, particularly along the island mountain ranges. But by Saturday afternoon, a return to calmer conditions is expected.

Mixed Precipitation/Freezing Rain Tonight:

With a shallow warm layer aloft over portions of central Montana there is a concern for freezing rain along portions of Highway 200 from Great Falls to Lewistown, I-15 from Great Falls to Helena and Highway 287 from Helena to Toston. Light freezing rain has already been reported south of Great Falls although ice accumulations have been very minimal at best so far. The biggest concern is that as soon as the sun sets tonight the roads will start to freeze up which could create a dangerous situation even if precipitation has ended.

When considering the potential for additional advisories/warnings, there is not currently enough confidence in significant ice accumulations to add an additional Winter Weather Advisory at time time. However this will be monitored very closely over the next few hours as even a slight uptick in freezing rain amounts beyond what it current forecasted and expected could quickly cause dangerous road conditions across portions of central Montana.

In the meantime, motorists need to be prepared for sudden changes to road conditions and keep in mind that ice can be almost impossible to see at night. If possible, folks should delay travel at least until temperatures warm up late tomorrow morning to avoid putting themselves in a potentially hazardous situation.

Bitter Cold Along the Hi-Line:

Another round of sub-zero lows is expected across the Hi-Line tonight with the coldest temperatures expected in northern Blaine county. A Cold Weather Advisory has been issued for northern Blaine overnight as apparent temperatures could drop as low as 30 below, especially out towards the Turner area.

Temperatures will warm up into the single digits above zero Saturday morning with one more round of cold temperatures expected Saturday night into Sunday morning before a warm front is able to advance towards the Hi-Line. With the warm front expected to arrive overnight, there is lower confidence that our portion of the Hi-Line will reach advisory criteria again. However there are three factors at play that could easily nudge the situation in either direction. The first is the location and progression of the warm front, the wind speeds, which are currently expected to remain light and variable, and the final snowpack in the region after the snowband has dissipated. If any of these factors deviates from what is currently expected in the forecast then an advisory may need to be considered for northern Blaine county Saturday night into Sunday. But for now, confidence is too low in reaching advisory level temperatures to warrant extending the current advisory through Sunday morning.

Warmer Temperatures Return:

Both the GFS and Euro ensembles are in agreement that temperatures will warm back into 40s and 50s across the lower elevations through at least the middle of next week. What happens closer to Christmas ends up being a bit of a wild card as there are some suggestions in the ensembles that another colder and active period could return to the region. But given how far out this is, no finer details will be resolved at this point in time. -thor

AVIATION

13/06Z TAF Period

VFR conditions will prevail across the KBZN, KEKS, KHLN, and KGTF terminals during this TAF Period. At the KHVR, KCTB, and KLWT terminals snow and/or low ceilings will reduce flight category to at least MVFR-levels for at least the first 8 hours of this TAF Period. At the KGTF terminal there is a 20 - 30% chance for snow between 13/07Z and 13/18Z. There will be isolated instances of low-level wind shear and mountain wave turbulence through 13/18Z across North-central, Central, and Southwestern Montana. There will also be instances of mountain obscuration across North- central Montana through at least 13/18Z. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 4 34 22 50 / 30 20 0 0 CTB -2 27 15 46 / 60 10 0 0 HLN 16 42 28 51 / 10 10 0 0 BZN 33 49 26 54 / 0 0 0 0 WYS 19 37 12 44 / 0 0 0 0 DLN 32 51 28 53 / 0 0 0 0 HVR -8 7 1 43 / 100 10 0 0 LWT 4 31 21 49 / 60 30 0 0

TFX WATCHES/WARNINGS/ADVISORIES

Winter Storm Warning until 5 AM MST Saturday for Bears Paw Mountains and Southern Blaine-Eastern Toole and Liberty-Fergus County below 4500ft-Hill County-Northern Blaine County-Western and Central Chouteau County.

Winter Weather Advisory until 5 AM MST Saturday for Eastern Glacier, Western Toole, and Central Pondera-Northern High Plains.

Cold Weather Advisory until 10 AM MST Saturday for Northern Blaine County.