textproduct: Great Falls

KEY MESSAGES

- Another wave of light rain and snow will move northeastward through central and southwest Montana today.

- A moist Pacific low pressure system will bring widespread rain and snow Thursday into Friday with the greatest winter impacts over the central island ranges and the higher terrain of southwest Montana.

- Drier and milder conditions move in for the weekend, although passing weather systems will bring breeziness and lower end shower activity, mostly over mountain areas.

DISCUSSION

/Issued 413 AM MDT Tue Mar 31 2026/

- Meteorological Overview:

Areas of light snow over southwest Montana are diminishing tonight as the responsible H700 frontogenesis weakens and slows down before retreating back northward later today. This will send another wave of scattered light rain/snow and even a rumble of thunder over southwest and portions of central MT. Today will be another cool day for much of the forecast area thanks to cool low level easterly flow, with milder temperatures returning by Wednesday in advance of the next Pacific trough.

Ensembles continue to favor a moist mid- level low pressure system crossing the Continental Divide into north-central and southwest MT and bringing widespread rain and snow Thursday into Friday. Areas along the divide and over the higher terrain of the southwest will begin seeing snow as early as Wednesday before snow levels begin to crash and snow increases in a west to east fashion on Thursday. While most lower elevation areas will get at least some snow by Thursday night, mountain areas look to see the highest snow totals and overall most significant impacts. The snow will be wet and will be accompanied by gusty north to northwesterly winds Thursday afternoon through Friday morning.

A drier northwesterly flow aloft will be left in the wake of the departing low heading into the weekend. This will generally bring drier and milder conditions; however, subtle shortwaves will pass through and bring periods of breezy to windy conditions and widely scattered shower activity, mostly over and near areas of higher terrain. - RCG

- Forecast Confidence & Scenarios:

Scattered areas of snow over southwest and portions of central MT through Wednesday morning...

Warm air advection ahead of a approaching shortwave will bring more areas of rain and snow over central and southwest MT today. I'm not expecting this to be too much of an impact, especially later in the day with diurnal heating and continued warming aloft. Although convective showers may bring isolated and localized pockets of heavier snow bursts, the probabilities for 2 or more inches of snow are mostly nil. The notable exception is for areas over and near the Gallatin/Madison ranges where there's a 70% + chance for 2+ inches. But even here, impacts should be on the minor side and mostly confined to brief periods this morning and then again later this evening into the early overnight hours.

Widespread snow developing from west to east Wednesday night through early Friday...

Snow will develop over the higher terrain along the Continental Divide and southwest MT by Wednesday night with impactful snow mostly staying above 6000 ft through Thursday morning. Cold air will then gradually bring snow levels down to the valley/plains during the day on Thursday. Although there are still some uncertainties to work out, the most impactful period looks to be later Thursday afternoon through Friday morning when the colder air becomes more established and north to northwesterly surface winds increase and gust in the 30 to 40 mph range at times.

Currently, most mountain areas have over a 50% chance for over one inch of liquid equivalent for this event, highest over the central island ranges and the mountains of Gallatin and Madison counties. Similarly, most lower elevation locations have over a 50% chance for a half inch or more of rainfall/liquid equivalent with the exception of areas along the Hi-Line and the drier southwest valleys south of I90 and near I15. The aforementioned mountain areas have over a 70% chance for snowfall totals in the 10 to 20 inch range.

There's much less confidence for lower elevation snow accumulation given temperatures looking to be just cold enough for snow in addition to the increasing sun angle essentially canceling out much of the opportunity for daytime roadway accumulations. Having said that, the northwesterly flow wrapping around the backside of this system is quite favorable for snow impacts for the central MT highway 87/200 corridor between Great Falls and Lewistown. Other northwesterly favored areas such as the Bozeman area will also need close monitoring. Impacts from this system may include slippery/slushy roads, cold, wet conditions for newborn livestock, and even scattered power outages from the combination of wet, heavy snow and gusty north/northwesterly winds. The first set of winter storm watches were sent out with this forecast package, including most mountain areas over central and southwest MT. The only lower elevation area included in the watch at this time is the central MT highway 87/200 corridor. More adjustments will be done once confidence increases for more precise storm tracking and lower elevation snow impacts. - RCG

AVIATION

31/18Z TAF Period

VFR conditions will prevail at all terminals except for the KBZN and KEKS terminals during this TAF Period. At the KBZN terminal there will be snow showers possibly mixed with rain through 01/03Z which will reduce visibility to MVFR levels. At the KBZN and KEKS terminals there will be IFR level ceilings for at least the first few hours of this TAF Period. At the KLWT and KHLN terminals between now and 01/06Z there is a 15 - 40% chance for snow showers. At the KBZN and KEKS terminals after 01/02Z through the end of the TAF Period there is a 15 - 50% chance for snow and rain showers during the duration of this TAF Period. During the duration of this TAF Period there will be mountain obscuration across Southwestern Montana with periods of mountain obscuration in Central Montana. -IG

PRELIMINARY POINT TEMPS/POPS

GTF 44 28 57 36 / 20 10 20 70 CTB 40 20 52 30 / 0 0 10 50 HLN 48 29 56 35 / 50 30 60 90 BZN 46 27 56 33 / 80 70 70 80 WYS 45 30 47 30 / 70 90 80 100 DLN 51 33 56 34 / 80 50 70 70 HVR 42 23 54 30 / 0 0 0 30 LWT 36 23 52 30 / 40 30 20 50

TFX WATCHES/WARNINGS/ADVISORIES

Winter Storm Watch from Thursday morning through late Thursday night for Elkhorn and Boulder Mountains-Northwest Beaverhead County-Southern Rocky Mountain Front-Upper Blackfoot and MacDonald Pass.

Winter Storm Watch from Thursday afternoon through Friday morning for Big Belt, Bridger and Castle Mountains-Cascade County below 5000ft-Fergus County below 4500ft-Gallatin and Madison County Mountains and Centennial Mountains-Judith Basin County and Judith Gap-Little Belt and Highwood Mountains-Snowy and Judith Mountains.