textproduct: Great Falls

KEY MESSAGES

- Strong and gusty west winds will gradually subside through the evening hours tonight.

- A strong cold front will bring falling temperatures and increasing chances for snow on Saturday, with snow persisting through the day on Sunday.

- Heavy, wet snow accumulating on trees with foliage may result in falling branches.

DISCUSSION

/Issued 203 PM MDT Fri Oct 9 2026/

- Meteorological Overview:

The next incoming trough coming down from Canada will bring an increase in winds aloft today. These stronger winds aloft will mix down to the surface from day time vertical mixing. The combination of the warm, breezy, and dry conditons will bring elevated to critical fire weather conditions to the region. Temperatures are also expected to peak today, with numerous lower elevation locations reaching into the 80s.

Saturday, an elongated trough coming in from Canada will bring a multi-day weather system through Montana. A cold front passing from north to south Saturday morning bring the first rush of cooler air to the region along with mountain snow and lower elevation rain/snow. Lee troughing with northerly cold air advection continues behind the front, and transitions rain to snow at lower elevations by Saturday evening. Meanwhile the front progression slows down heading into Southwest MT, which delays the switch over the snow later than North-Central MT. Strong convergence and frontogenesis also occurs along this front as it head into North-Central/Central MT, which can develop moderate to heavy snow banding. Northerly flow in North-Central MT will allow for enhanced snowfall for northerly upslope areas of the Little Belts/Central Continental Divide. Temperatures don't look to warm up much heading into Sunday. Increasing moisture from the remnant southwest tropical storm system will continue to feed moisture into this storm system Sunday into Monday before exiting later in the day Monday.

Behind this system, another quick moving trough looks to swing through Wednesday into Thursday, which will keep the cooler temperatures and chances of precipitation. However, details with this will be heavily dependent on what happens this weekend/Monday.

- Forecast Confidence & Scenarios:

Cold Front and Temperatures Saturday and Sunday...

A strong cold front will move south from Alberta tonight and through the day on Saturday, with high confidence that the aforementioned front will bring a sharp drop in temperatures along with gusty north winds of between 35 to 45 mph to all locations upon its passage. At this time the following locations can expect the cold front to pass through between midnight and 3AM (Cut Bank), 3AM and 6AM (Great Falls), 6AM and 9AM (Havre), 9AM and noon (Lewistown, Helena, and White Sulphur Springs), noon and 3PM (Bozeman), and 3PM and 6PM (Dillon and Ennis). Should the cold front arrive sooner than expected at any given location then high temperatures for the day on Saturday will be much lower than currently forecasted, with a later arrival of the front having having the opposite effect on high temperatures (i.e. warmer than currently forecasted). The arrival time of the front will also be crucial in how quickly ground temperatures cool to support snowfall accumulations later on during the event, with an earlier arrival allowing for more time for the antecedent warm ground to cool. Be prepared for a significant change from the warm conditions as of late to more winter like temperatures this weekend

Snowfall Amounts from Saturday afternoon through Monday morning...

Snowfall amounts over the past 12 hours continue to trend up over the plains of Central Montana along and south of the Montana Hwy 200 corridor and north of the US Hwy 12 corridor, most notably in northerly upslope areas along and north of the Little Belt and Snowy Mountains where the flow is likely to become blocked leading to precipitation backing off of the adjacent terrain. While warm ground temperatures and the still "high" October sun angle will reduce snowfall accumulations on road surfaces and sidewalks, slippery and snow packed surfaces are still expected to develop due to the timing of the heaviest snow occurring from Saturday evening through Sunday morning. Additionally, periods of moderate to heavy snow, with snowfall rates of between 0.5" to 1" per hour, associated with an area of strong frontogenesis will help to offset the effects of the warm ground. In addition to the impacts to travel the wet and heavy nature of the snow could lead to tree damage, especially to those tress that still have foliage. Gusty north winds and the heavy, wet snow accumulating on power lines may also lead to isolated power outages; with the biggest concern for power outages occurring across the Southern Rocky Mountain Front and Montana Hwy 200 corridor.

With the exception of the Gallatin and Madison County Mountains and Centennial Mountains, where the Winter Storm Watch was upgraded to a Winter Weather Advisory, all of the Winter Storm Watches for Central Montana were upgraded to a Winter Storm Warning and extended through Monday morning. Additionally, the Snowy Mountains were also added to the Winter Storm Warning. For all other areas outside Hill County and Northern Blaine County a Winter Weather Advisory is now in effect from Saturday evening through Monday morning. Should mesoscale snow banding occur outside of the current Winter Storm Warning area then some of the areas covered by an advisory may need to be upgraded. The area of greatest concern for this mesoscale snow band to develop would be the Helena Valley, northern portions of the Canyon Ferry Area, and lower elevations of Southern Fergus County.

Below is a table for snowfall amounts at select locations across North Central, Central, and Southwest Montana for the Low End (10Pct), Most Likely (50Pct), and High End (90 Pct) scenarios.

48hr Snowfall (18z Sat thru 18z Mon) LOCATION NBM 10Pct | NBM 50Pct | NBM 90Pct Browning 4.4 | 6.5 | 10.5 Cut Bank 2.9 | 4.2 | 5.0 Havre 0.0 | 0.3 | 0.3 Great Falls 4.6 | 6.5 | 9.0 Lewistown 6.5 | 8.0 | 9.5 Helena 3.2 | 4.4 | 5.6 White Sulphur Springs 5.4 | 7.0 | 9.0 Bozeman 2.6 | 3.4 | 3.8 Dillon 1.5 | 2.3 | 2.6 Ennis 2.3 | 4.6 | 5.2 West Yellowstone 0.2 | 0.4 | 0.4

- Moldan

AVIATION

10/00Z TAF Period.

VFR conditions will start off the first 6 hours of the TAF period before the front moves through and leads to a wind shift to the north with low clouds and precipitation slowly filling in across the region from north to south.

North-Central Montana and Central Montana: Gusty winds will redevelop along the Rocky Mountain Front into the northern plains Saturday morning with gusts up to 40kts possible. Precipitation chances start to increase from north to south after 10/12Z and through 10/18Z, the dominant precipitation type at terminal level will be rain with rain switching to snow after 10/18Z. There is some uncertainty in how fast the transition from rain to snow and it is likely to vary by terminal but there is a chance that terminals such as KCTB and KGTF may have a faster transition to snow than KLWT and KHVR. MVFR and IFR conditions are expected at all terminals with periods of LIFR conditions possible under heavier showers, particularly KGTF and KHLN. Mountain obscuration will remain a concern after 10/06Z along the Continental Divide and after 10/10Z for the island mountain ranges of Central Montana. The lowering of the cloud deck is generally expected to occur 2 to 4 hours before precipitation starts filling in around the surrounding mountains and an additional 2 hours before precipitation is expected at terminal level.

Southwest Montana: Gusty winds will taper off for KBZN and KWYS after sunset with KEKS expected to have continued gusty winds through the period as winds are funneled through the Madison Valley. Winds will pick up once again on Saturday afternoon as precipitation starts to fill in and cloud levels continue to drop leading to mountain obscuration after 10/14Z. At surface level for all southwest terminals, the dominant precipitation type will be rain with a chance for snow levels above 8000ft through 11/00Z and dropping below that towards Saturday evening into Sunday morning. Thus the transition to snow is not expected to occur until after the end of the current TAF period. Regarding flight categories, KEKS and KWYS are expected to remain at VFR with only low probabilities (<10%) of reaching MVFR which would most likely be a result of isolated shower and thunderstorm activity along the Montana/Idaho border potentially impacting KWYS. KBZN, on the other hand, will be much more prone to VIS and CIG reductions as the heavier precipitation is expected to reach the Gallatin Valley towards the end of the TAF period. MVFR and IFR conditions can be expected for KBZN after 11/00Z with a 10% chance for LIFR conditions through 11/06Z. -thor

FIRE WEATHER

A Red Flag Warning remains in effect for portions of North Central and Southwest Montana through this evening due to low humidity, gusty winds, and warm temperatures. A strong cold front advancing south through Montana tonight and into the day on Saturday will bring cooler temperatures, higher humidity, and widespread precipitation. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 37 42 27 33 / 10 100 100 100 CTB 32 37 24 32 / 20 40 90 100 HLN 42 45 28 33 / 10 90 100 100 BZN 43 58 28 34 / 30 80 100 100 WYS 36 55 30 43 / 10 80 100 100 DLN 45 58 27 33 / 20 60 90 100 HVR 37 48 26 38 / 10 60 80 90 LWT 42 49 27 33 / 30 80 100 100

TFX WATCHES/WARNINGS/ADVISORIES

Winter Storm Warning from 6 PM Saturday to 6 AM MDT Monday for Big Belt, Bridger and Castle Mountains-Cascade County below 5000ft-Eastern Pondera and Eastern Teton-Elkhorn and Boulder Mountains-Judith Basin County and Judith Gap-Little Belt and Highwood Mountains-Meagher County Valleys-Snowy and Judith Mountains.

Winter Weather Advisory from 6 PM Saturday to 6 AM MDT Monday for Bears Paw Mountains and Southern Blaine-Beaverhead and Western Madison below 6000ft-Canyon Ferry Area-East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera- Eastern Toole and Liberty-Fergus County below 4500ft-Gallatin Valley-Gallatin and Madison County Mountains and Centennial Mountains-Helena Valley-Madison River Valley-Missouri Headwaters- Northern High Plains-Northwest Beaverhead County-Ruby Mountains and Southern Beaverhead Mountains-Western and Central Chouteau County.

Winter Storm Warning from noon Saturday to 6 AM MDT Monday for Gates of the Mountains-Southern High Plains-Southern Rocky Mountain Front-Upper Blackfoot and MacDonald Pass.

Red Flag Warning until 9 PM MDT this evening for Central and Eastern Lewis and Clark National Forest Areas-Helena and Townsend Ranger Districts of the Helena National Forest.