A disturbance moving over the Treasure State brought increasing winds and clouds to the plains, while continuing very warm and dry conditions across the region.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS TFX wrote it up.
A disturbance moving over the Treasure State brought increasing winds and clouds to the plains, while continuing very warm and dry conditions across the region.
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 Sep 17, 10:13 PM MST, 32 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 1113 PM MDT Sun Sep 17 2023 ...Aviation Section Updated... .SYNOPSIS... Expect increasing clouds, as the last very warm day for awhile gives way to slightly cooler temperatures on Monday. There will even be a chance for an afternoon thunderstorm over Southwest MT. For Tuesday and Wednesday, expect much cooler temperatures to move into Montana, with afternoon highs only in the 50s and 60s by Wednesday. Additionally the chance for rain and high mountain snow will start to increase Wednesday night, with periods of rain and mountain snow looking more likely by Friday. && .UPDATE... The current forecast is doing well, so no changes were made tonight. RH values are currently between 15 and 25 percent and will have poor recovery tonight across North Central Montana. Wind gusts continue to diminish through the overnight hours tonight, picking back up tomorrow afternoon for another windy day. Webb && .AVIATION... 1113 PM MDT Sun Sep 17 2023 (18/06Z TAF Period) VFR conditions prevail this TAF period. Gusty westerly winds will resume Monday morning across the plains of North-central Montana, spreading into much of Central and Southwest Montana by the afternoon. Otherwise, scattered showers and thunderstorms are expected late Monday afternoon and early evening across Southwest Montana, primarily near the Idaho border. Gusty erratic winds will be the concern with thunderstorms that do form. -AM Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .FIRE WEATHER... Red Flag Warning will continue into Monday evening. Expect gusty winds and low humidity during the afternoon and evening hours. Some improvement overnight tonight, but critical fire weather conditions will then redevelop on Monday afternoon. Cooler temperatures and higher humidity expected to move into the area on Monday night. Brusda && .PREV DISCUSSION... /ISSUED 517 PM MDT Sun Sep 17 2023/ Tonight through Monday...Clouds will continue to increase over the CWa this evening, as the upper level ridge begins to break down and shift to our east. It will remain windy tonight, especially over North Central MT. This should keep overnight temperatures a bit warmer than previous nights. On Monday afternoon, an upper level disturbance will move through Southwest MT, producing a few afternoon showers/thunderstorms. It will continue to be windy over North Central MT, but not quite as warm. Monday night through Wednesday. Expect cooler air to continue to move into the CWA each day, with afternoon temperatures cooling about 10 degrees each day for Tue/Wed. The chances for precipitation will still be fairly low for Tue/Wed as the region will be in between storm systems. Wednesday night through Sunday...Expect a rather unsettled period of weather during this period. The chances for rain and high mountain snow will start to increase quite a bit Wednesday evening, and by Friday, a rather wet period is looking possible over portions of the CWA. Snow levels continue to go up, and are generally above 7500 feet. Precipitation amounts of around one half inch are looking possible, with isolated higher amounts in the higher elevations south of Lewistown. Otherwise, by next Sunday, expect drier conditions to move back into the CWA, along with a return to near normal temperatures. Brusda && .PRELIMINARY POINT TEMPS/POPS... GTF 56 78 47 68 / 0 10 10 0 CTB 51 73 40 63 / 0 0 10 0 HLN 54 81 49 72 / 0 0 20 0 BZN 47 81 43 70 / 0 20 20 0 WYS 36 69 35 64 / 0 20 20 10 DLN 44 76 41 68 / 0 10 10 0 HVR 53 81 45 69 / 0 0 10 0 LWT 52 79 45 67 / 0 0 20 10 && .TFX WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 9 PM MDT Monday for Chouteau and Fergus Counties-Eastern Glacier/Toole/Central/Eastern Pondera/Liberty- Hill and Blaine Counties-Lewis and Clark National Forest Rocky Mountain District-Rocky Mountain Front. && http://www.weather.gov/greatfalls
The national radar mosaic for the moment the first event began.
3 high wind. Local standard time, as filed.
Mesonet station DELMT Dellwo measured 62 mph wind gust.
Mesonet station DCRM8 Deep Creek RAWS measured 70 mph wind gust.
Mesonet station TR276 L-C Portable No. 1 measured 60 mph wind gust.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2023Every state in 2023This day in weather historyWarnings in Montana, September 2023
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: 1128853, 1128850, 1128855.