textproduct: Great Falls

KEY MESSAGES

- First round of snow tonight will primarily focus on the mountains of central and southwest Montana with significant travel impacts expected along the mountain passes.

- A lull in heavy snow is expected late Friday morning through the afternoon.

- The second round of snow will arrive late Friday afternoon and have more widespread impacts both in the mountains and potentially across the lower elevations.

UPDATE

/Issued 842 PM MST Thu Dec 4 2025/

Northwest flow aloft will continue to bring down mini shortwaves through the night. This will continue to bring snow across Central and Southwest MT, with more moderate to heavy snow in the mountains. Moderate to heavy snow should lighten up Friday morning. Temperatures dropping down into the 20s to teens will result in wet pavements refreezing overnight and cause slick driving conditions. Current winter products in affect this evening still remain on track. -Wilson

DISCUSSION

/Issued 842 PM MST Thu Dec 4 2025/

- Meteorological Overview:

There will be two rounds of heavy snow expected over the next few days. The first round is ongoing and will last through Friday morning with the most of the impacts expected in the mountains of central and southwest Montana as well as Gallatin Valley and Boulder Hill.

There will be a lull in the activity with lighter mountain snow late Friday morning through late Friday afternoon with the second wave of snow arriving by the evening. The second round will be more widespread with the potential for lower elevation snow along the valleys and northern plains.

- Forecast Confidence & Scenarios:

The mountains will receive the heaviest amounts and are thus the focus of the current Winter Storm Warnings. Travel along mountain passes will be hazardous at times with reductions in visibility, slippery conditions, and rapidly changing conditions among the expected hazards. The hardest impacted passes and roads include Kings Hill, Deep Creek, and Bozeman Passes and Highway 191 south of Bozeman to the Idaho border. Motorists traveling along these roads should carry an emergency kit in their vehicle and be prepared for potential travel delays along their commute.

Gallatin Valley/Bozeman/Boulder Hill Snow:

While the heaviest amounts are still confined to the mountains, there is increasing concern for impacts in Boulder Hill and Bozeman proper tonight through Friday morning associated with this first wave of snow. Travel concerns remain at the top of the list for potential impacts. One particular concern is that the initial snowfall will melt on the pavement and combine with any other snowmelt from the day which will then refreeze as the night goes on. This may create a thin layer of ice along area roads which, with additional snowfall expected through the night, may make for difficult travel at times. Because of the potential impact to travel along with the 2 to 4 inches of snowfall expected through tomorrow morning, the decision was made to put Gallatin Valley and Boulder Hill in a Winter Weather Advisory.

Additional snowfall is expected with the second wave but because there is a 12-18 hour lull in snowfall expected between rounds of snow, for now, the focus will be on tonight and the potential headlines for tomorrow will be addressed with later forecast packages. Additionally there is some guidance in the hi-res models that a snowband may set up around the Gallatin Valley at some point with the second round which could produce higher snowfall amounts and greater impacts in the Gallatin Valley which could potentially make it a candidate for a warning tomorrow. But because confidence is low in the snowband, Gallatin Valley will not be added to a watch at this time. But folks in the area should prepare for difficult driving conditions Friday evening through Saturday morning as well.

Lower Elevation Snow Friday/Saturday:

There is growing confidence in a snowband setting up across north-central Montana. The problem is this is turning out to be a scenario of high confidence in a snowband occurring, low confidence in where exactly the snowband sets up. What this means for messaging of impacts is that most locations across the northern plains can reasonably expect 1 to 2 inches of snow Friday and Saturday with the second wave. Where the snowband sets up is where locations may see 4 to 6 inches of snow with potentially higher amounts locally. For now this appears to be a solid advisory criteria event, however, there are some suggestions in the models that a couple areas could reach warning criteria. But because there is such low confidence in where the heavier snow amounts will be located and things keep changing with every model update, there is simply not enough to issue any headlines at this point until updated hi-res model guidance arrives that gives a clearer picture on what might unfold. In the meantime, folks across the northern plains should be prepared for general winter weather conditions with the understanding that if they are under the snowband there could be periods of moderate to heavy snow with significant reductions in visibility possible along area roads. -thor

AVIATION

05/06Z TAF Period

Light snow continues for Southwest MT and KLWT overnight and into the morning. Light snow will bring periods of MVFR/IFR conditions. There will be a lull in snow Friday morning/afternoon before a front brings steadier snow rates Friday evening. Temperatures will be hovering just above or at freezing when this moves through. There's some uncertainty if precipitation will be a rain/snow mix, or if snow rates will be moderate enough for snow to be the dominant precipitation type. This front will bring better chances for prevailing MVFR with periods of IFR/LIFR conditions. -Wilson

PRELIMINARY POINT TEMPS/POPS

GTF 22 37 21 33 / 20 40 80 50 CTB 15 30 10 25 / 10 40 90 30 HLN 24 37 29 40 / 40 50 90 60 BZN 23 36 26 39 / 100 60 90 60 WYS 15 30 19 33 / 90 90 100 80 DLN 23 39 27 40 / 50 50 70 20 HVR 18 29 9 22 / 20 40 90 60 LWT 21 34 19 33 / 60 40 90 70

TFX WATCHES/WARNINGS/ADVISORIES

Winter Storm Watch from Friday afternoon through Sunday morning for East Glacier Park Region-Southern Rocky Mountain Front.

Winter Storm Warning until 2 PM MST Saturday for Big Belt, Bridger and Castle Mountains-Gallatin and Madison County Mountains and Centennial Mountains-Little Belt and Highwood Mountains.

Winter Weather Advisory until 11 AM MST Friday for Elkhorn and Boulder Mountains-Gallatin Valley.

Winter Storm Warning until 5 PM MST Saturday for Northwest Beaverhead County.