textproduct: Great Falls

KEY MESSAGES

- Icy conditions are expected due to freezing rain and snow across Lewis and Clark and Broadwater counties this morning.

- Snow increases across north-central Montana this morning with moderate to heavy snow expected across eastern portions of north- central Montana into this evening.

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

DISCUSSION

/Issued 346 AM MST Fri Dec 12 2025/

- Meteorological Overview:

Deep upper level troughing across Canada brought an arctic airmass south across the North-central MT plains yesterday with shallow cold air trickling south through the Helena valley and Canyon Ferry area overnight as well as across the continental divide near Rogers PAss through Lincoln. Meanwhile upper level ridging remains in place off the west coast with mild air remaining across southwest MT while a plume of PACific moisture continues to stream over the ridge and across central and north-central MT. An area of widespread precipitation across central MT early this morning will lift north today and intensify as the upper ridge begins to shift inland and deeper moisture overruns the cold airmass.

Freezing rain that occurred overnight from Lincoln southeast through Helena and Townsend has largely changed to snow early this morning as the cold air deepened somewhat, but mid level warming is likely to change precipitation back to freezing rain for period this morning before the precipitation lifts northward of this area by this afternoon. Further north, the best forcing for moderate to heavy snowfall is expected to develop from Toole county southeast through Choteau and Fergus counties this afternoon, shifting northward Hill and Blaine counties this evening.

As the upper level ridge continues to shift inland this weekend, The cold airmass will retreat back to the north with mild and windy conditions overspreading the entire area by Sunday and continuing through at least Monday. Hoenisch

- Forecast Confidence & Scenarios:

An ice storm warning has been issued for the Upper Blackfoot, Helena and Canyon Ferry areas where roads may be particularly icy this morning. Snow may conceal the ice in some areas and additional icing is expected as precipitation changes back to freezing rain with road and air temperatures remaining in the teens in these areas this morning.

Fore snowfall amounts and winter weather hazards across north- central MT remain on track from previous forecasts with heaviest snowfall amounts likely along an axis from Liberty and Hill counties southeast through Fergus county. Hoenisch

AVIATION

12/12Z TAF Period

MVFR conditions remain widespread across most TAF sites today with IFR conditions becoming more widespread this 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, a switch back to freezing rain is likely at KHLN this morning with lower confidence in potential for -FZRA at KBZN. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 11 5 37 20 / 100 50 10 0 CTB 4 0 29 13 / 80 70 0 0 HLN 39 25 44 29 / 90 20 10 0 BZN 49 33 48 26 / 60 10 0 0 WYS 40 20 39 12 / 40 0 0 0 DLN 53 33 52 28 / 10 0 0 0 HVR 0 -8 7 0 / 100 100 10 0 LWT 14 2 34 23 / 100 70 20 0

TFX WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory until 10 AM MST this morning 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 Bears Paw Mountains and Southern Blaine-Eastern Toole and Liberty-Fergus County below 4500ft-Hill County-Judith Basin County and Judith Gap-Northern Blaine County-Western and Central Chouteau County.

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

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

Ice Storm Warning until 10 AM MST this morning for Canyon Ferry Area-Helena Valley-Upper Blackfoot and MacDonald Pass.

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