A Canadian cold front pushed south on Sunday, which brought isolated strong winds near on the downslope side of the Sweet Grass Hills.
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The episode as NWS TFX wrote it up.
A Canadian cold front pushed south on Sunday, which brought isolated strong winds near on the downslope side of the Sweet Grass Hills.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Great Falls, MT wrote its last area forecast discussion before the first event at May 4, 4:45 AM MST, 10 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Great Falls MT 545 AM MDT Sun May 4 2025 Aviation Section Updated. .KEY MESSAGES... - Active weather through Tuesday with widespread soaking rain and some mountain snow. - Warmer and drier for midweek as upper level ridging builds into the area. - Additional light rainfall possible late Thursday or Friday. && .DISCUSSION... /Issued 410 AM MDT Sun May 4 2025/ - Meteorological Overview: Upper level ridging that was present over the Northern Rockies late last week will continue its trek to the east today, allowing a deep upper level trough to take its place. As it does so, temperatures will fall from the 80s yesterday to the 50s along the divide, with 60s and low 70s for most of the rest of the area today. In addition to the cooler temperatures today, a few showers and thunderstorms are expected to develop during the afternoon, first across Southwestern Montana before spreading further north and spreading across the plains during the evening hours. Rain will continue into the day on Monday as difluence sets up aloft, potentially allowing for a band of heavier precipitation to set up in an SW to NE line. As the rain continues to fall on Monday, cooler air will continue to pour into the Northern Rockies, which will cause snow levels to gradually lower, eventually reaching as low as 5000 feet or so. This will bring some late season snowfall to the mid and upper elevations. While accumulations will generally be on the lighter side (1-2 inches outside of the Little Belts), the heavy, wet nature of the snowfall may still result in some damage to vulnerable trees. Upper level ridging will return to the area for the second half of the week, allowing temperatures to climb back to above average for the second half of the week. While most of the second half of the week will be dry, a passing disturbance may allow for a few showers to develop around Thursday as the ridge builds. - Forecast Confidence & Scenarios: The main area of uncertainty remains with the upcoming rain event early this week. Overall, there seems to be good agreement in a widespread soaking rainfall across North Central and Southwestern Montana. However, the placement of the heaviest rainfall remains a point of contention between differing solutions. On one hand, a few models have been suggesting a widespread light rainfall across the area, with precipitation totals generally falling under a half inch for most. On the other, a few models (including some higher resolution guidance) have seemed to hint in divergence aloft resulting in a widespread area of light rainfall, with a more focused area of more intense rainfall along a SW to NE oriented axis. This latter idea seems to fit better with the conceptual model (what makes sense meteorologically) with an upper level low setting up to the south, and the NBM seems to do a decent job of capturing this possibility, putting the area of heaviest precipitation along a line roughly from Helena to Great Falls to Havre, where a half inch to an inch of precipitation seems likely, with lesser (but still highly beneficial) amounts of rainfall elsewhere across the area. For now, I like the amounts I have in the forecast grids, though I wouldn’t be overly surprised if we see a few reports of 1-1.5 inches of rainfall come in along this line, wherever it sets up. Ludwig&& .AVIATION... 04/06Z TAF Period While VFR conditions are expected to prevail through the overnight hours, expect conditions to gradually degrade through the day on Sunday as clouds lower and rain showers (and a few thunderstorms) develop, starting in Southwestern Montana before spreading northward to North Central Montana. Best chances for Thunderstorms will be around KEKS, KBZN, and KWYS, where some hail to a half inch in diameter will be possible. Ludwig Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .AVIATION... 04/12Z TAF Period While VFR conditions are expected to prevail through the morning hours, expect conditions to gradually degrade through the day today as clouds lower and rain showers (and a few thunderstorms) develop, starting in Southwestern Montana around 21z before spreading northward to North Central Montana around 0z or so. Best chances for thunderstorms will be around KEKS, KBZN, and KWYS, where some hail to a half inch in diameter will be possible. Rain will become widespread overnight Sunday and early Monday, and some mountain obscuration is expected through the TAF period. Ludwig Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 67 39 50 32 / 30 100 100 10 CTB 55 37 54 30 / 60 80 40 0 HLN 68 40 50 33 / 60 100 100 20 BZN 73 38 46 30 / 60 90 90 40 WYS 70 35 49 27 / 30 60 60 40 DLN 71 37 47 31 / 70 90 60 20 HVR 71 39 57 32 / 10 100 100 0 LWT 69 36 43 31 / 10 80 100 40 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 9 PM this evening to noon MDT Monday for Little Belt and Highwood Mountains. && http://www.weather.gov/greatfalls
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
MT Mesonet site Mt Lebanon measured sustained high winds of 41 mph. It also measured a high wind gust of 61 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2025Every state in 2025This day in weather historyWarnings in Montana, May 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1256162.