textproduct: Great Falls

KEY MESSAGES

- Above normal temperatures and gusty conditions continue today.

- Windier conditions are expected on Monday as a cold front moves across the Northern Rockies, with increasing precipitation chances and mountain snow.

- Much colder conditions are expected for next weekend.

DISCUSSION

/Issued 308 AM MST Sun Nov 23 2025/

- Meteorological Overview:

Zonal flow over the Northern Rockies will yield one final day of well above normal temperatures across Southwest through North Central Montana, along with gusty southwest to west surface winds. Precipitation chances will begin to increase through the day today along the Continental Divide as Pacific moisture is advected northeast ahead of a shortwave sliding towards the Pacific Northwest. This shortwave will then slide east and over the Northern Rockies on Monday, with precipitation overspreading all of Southwest through North Central Montana. Precipitation through this timeframe will be heaviest over the mountains, and to the northwest of the surface low (i.e. Hi-Line), which is currently prog'd to track across Central Montana. A cold front diving southeast from Alberta and across Montana on Monday will lead to falling temperatures, with most locations across North Central and Central Montana seeing their highs occurring in the morning hours while Southwest Montana sees a more traditional timeframe for highs.

Northwest flow in wake of the shortwave on Monday will help to maintain daily chances for precipitation through the remainder of the work week, along with near normal temperatures. By Friday night a potent longwave trough will begin to dig south from Canada and over the Northern Rockies, with much colder air arriving to the Northern Rockies as an Arctic front pushes south from Canada. - Moldan

- Forecast Confidence & Scenarios:

Strong Winds on Monday...

NBM4.3 probabilities for wind gusts in excess of 48kts continue to remain relatively low, generally ranging from a 20-40% chance across any given location. While these values have changed little over the past 24 hours, which should help to boost confidence in high wind not materializing, BUFKIT soundings across Central Montana (i.e. Rogers Pass and Helena) support wind values of 40kts around 1500ft AGL and 50kts at 3000ft AGL overspreading the area between 19-23z. This timing, which is during peak mixing, also coincides with the passage of the shortwave moving over the Northern Rockies and increasing pressure rises pushing southeast behind a cold front diving southeast from North Central and into Southwest Montana. Furthermore, ECMWF EFIs with respect to wind gusts across Central Montana range from 0.6 to nearly 0.8, with these values supporting the potential for an unusual to very unusual wind event.

While not the most likely scenario there is the potential for a 1- 3hr window during the afternoon hours on Monday for several locations across Central Montana to exceed high wind criteria, with these areas being south of the Montana Hwy 200 corridor and north of the US Hwy 12 corridor. Given the continued low probabilistic support we will withhold issuing any High Wind Watches at this time, but should ECMWF EFI and/or BUFKIT values increase with subsequent model runs then future high wind highlights may be warranted.

Accumulating Snow from late Sunday night through Monday evening...

Winter Weather Advisories have now been issued for the Southern Rocky Mountain Front, Big Belt, Bridger and Castle Mountains, Little Belt and Highwood Mountains, Bears Paw Mountains and Southern Blaine County where probabilities for 4" or more of snow range from a 50- 75%. While initially warm ground temperatures will lead to some melting across these locations snowfall rates of 1/2" per hour or more during the daylight hours, which have a 30-60% chance of occurring, will lead to snow accumulating even on warm surfaces.

The Winter Weather Advisory for the East Glacier Park Region remains in effect; however, there is growing concern that the combination of heavy snow and strong winds could significantly reduce visibilities west of East Glacier and over Marias Pass. Additionally, probabilities for 8" or more of snow over Marias Pass are now at a 65% chance, with even a 25% chance of 12" or more of snow. Future shifts may need to consider upgrading the advisory to a warning, but for now we will hold onto the advisory to see if the trend for higher snowfall amounts holds. - Moldan

AVIATION

23/12Z TAF Period

VFR conditions are expected through 09z-12z Monday, with lowering CIGS from north to south thereafter as a cold front and upper level disturbance moves across the Northern Rockies. Prior to these features scattered to broken mid-level cloudiness will occur across all terminals as Pacific moisture streams eastward ahead of the upper level disturbance. Additionally, gusty southwest to west surface winds will continue across the plains of Central and North Central Montana through the day today, with stronger winds expected on Monday. Mountains will become increasingly obscured along the Continental Divide through 18z and 00z Monday points further east. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 55 39 45 21 / 20 30 80 50 CTB 50 31 36 14 / 10 20 90 30 HLN 45 34 40 19 / 10 20 80 30 BZN 50 32 44 14 / 0 20 80 10 WYS 43 24 34 3 / 0 20 80 20 DLN 49 32 45 11 / 0 10 50 0 HVR 55 29 39 16 / 10 20 90 60 LWT 56 34 44 17 / 10 20 80 40

TFX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from 11 PM this evening to 11 PM MST Monday for Bears Paw Mountains and Southern Blaine-Big Belt, Bridger and Castle Mountains-East Glacier Park Region-Little Belt and Highwood Mountains-Southern Rocky Mountain Front.