textproduct: Great Falls

KEY MESSAGES

- Wet snow and wind impacts through early this evening will diminish overnight.

- Greatest potential for moderate snowfall rates and windy conditions through early this evening across areas near the central Montana mountains

- Strong winds across portions of north-central MT diminish from west to east tonight.

- Drier but continued cooler than average conditions are expected for the weekend into early next week.

UPDATE

/Issued 650 PM MDT Fri Oct 23 2026/

The core of the upper level disturbance responsible for the cold front and associated winter weather is beginning to shift toward eastern MT this evening. In the meantime, a band of snow continues to shift eastward, across North-central through SW MT, diminishing or exiting east of the area by early Saturday morning. Snowfall rates in excess of a half inch per hour will continue with this band as it moves eastward. Areas near pass level continue to be the most impacted from this event, but impacts are forecast to increase this evening at lower elevations with the loss of daytime heating. Lewistown still looks to see greatest accumulations at lower elevations, with isolated amounts approaching 6 inches in the foothills to the south and east of town.

Strong wind gusts continue in areas lee of terrain in Fergus county. The High Wind Warning is in effect until 9 PM for this area, but it will be monitored for the potential to be extended a bit longer.

Otherwise the concern heading into Saturday will be for fog in areas that clear out and have sufficiently weak winds. At this point the SW MT valleys are most favored for the fog. -AM

DISCUSSION

/Issued 650 PM MDT Fri Oct 23 2026/

- Meteorological Overview:

A fairly vigorous mid level wave accompanied by anomalous moisture continues to lift north across central MT this afternoon ahead of an upper level trough tracking east across the Rockies. This will continue to support widespread precipitation across much of the area into early this evening before drying behind the eastward moving trough brings an end to precipitation from west to east late this evening/overnight.

Potential for embedded isolated thunderstorms and brief moderate- heavy precipitation rates will decrease late this afternoon as the strongest lift moves out of the area and stability increases. The risk for impacts from localized intense precipitation has also decreased as snow levels continue to lower, leading to reduced runoff.

Surge of colder air from Canada will continue to spread east across remaining eastern portions of north-central MT and south through the valleys of SW MT through the rest of this afternoon and evening, bringing a transition to wet snow to even the lowest elevations before precipitation ends later this evening. Strongest north/northwest winds with the initial surge of the cooler airmass across western portions of nort-central MT will begin to gradually decrease late this afternoon, while eastern portions of north-central MT will have winds peak late this afternoon but not likely to noticeably diminish until later tonight.

Moderate to heavy snowfall rates are most likely to occur late this afternoon with lingering anomalous moisture still in place ahead of the upper trough axis, with a transition to more orographic/up-slope forced snowfall occurring this evening before precipitation ends. High resolution model ensembles have the highest probabilities(80% or better) for 1"/hr rated across the Little Belt and N-central MT Island Ranges and nearby foothills between 4pm and 7pm with a 20-40% probability for adjacent portions of Fergus and Judith Basin counties including the Judith Gap and Lewistown areas.

A drier westerly flow moves across the Northern Rockies Saturday behind the departing system with a broad area of upper level troughing lingering across western Canada and extending to offshore of the US West Coast. This holds a cooler than average airmass across the region into early next week with surface high pressure centered over the Canadian Prairies and generally dry conditions prevailing through Monday. Medium range models are converging on the idea of a lobe of energy moving out of the larger scale trough across the NW US around Tuesday. This would be a colder system with lower snow levels to start, but would likely not have as much deep moisture available as the current system and there is still considerable uncertainty this this time with more specific details. Hoenisch

- Forecast Confidence & Scenarios:

Main concerns for winter weather impacts through the rest of this afternoon and evening are in areas that see the heavier snowfall rates in conjunction with windy conditions. This is most likely across areas near the Little Belts/Snowies and adjacent portions of Judith Basin, Fergus and southeastern Cascade counties. Hoenisch

AVIATION

24/06Z TAF Period

VFR conditions will prevail at all terminals except for at the KLWT terminal during this TAF Period. After 24/08Z clouds will lift at the KLWT terminal and VFR conditions will prevail through the end of the TAF Period. At the KBZN, KHLN, and KGTF terminals between 24/09Z and 24/14Z there is a low chance for fog to form. During the first few hours of this TAF Period there will be mountain obscuration across North-central, Central, and Southwestern Montana. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 25 43 25 38 / 100 0 0 0 CTB 21 42 23 39 / 0 0 0 0 HLN 21 44 24 42 / 80 0 0 0 BZN 21 41 20 43 / 100 0 0 0 WYS 15 46 15 50 / 90 0 0 0 DLN 25 44 24 46 / 100 0 0 0 HVR 23 44 22 44 / 100 0 0 0 LWT 21 40 21 39 / 100 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 3 AM MDT Saturday for Fergus County below 4500ft-Snowy and Judith Mountains.