A surface trough built in from the north from the Great Basin into the Northern Rockies, while southeasterly winds at the surface brought in low level moisture into the region. Pacific moisture increased in the upper levels as an approaching trough.
Every event with a place to put it. 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 surface trough built in from the north from the Great Basin into the Northern Rockies, while southeasterly winds at the surface brought in low level moisture into the region. Pacific moisture increased in the upper levels as an approaching trough. This combination lead to scattered showers and thunderstorms to development over the western and southwest mountains before moving out onto the plains that afternoon. Some thunderstorms produced large hail and one complex of storms with heavy rain and strong winds moved over the Great Falls area resulting reports of wind damage and urban flooding.
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 Jul 6, 4:35 PM MST, 25 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 535 PM MDT Sat Jul 6 2019 Updated Aviation Section .SYNOPSIS... An unstable southwest flow aloft will keep mostly afternoon and evening shower and thunderstorm activity going through early next week. Thunderstorms may become strong to severe today and Sunday, with hail, gusty winds, and heavy rain possible. Drier and warmer conditions are expected by mid-week. && .DISCUSSION... Remainder of this afternoon through Sunday Night...Our region continues to be situated in a moist and unstable flow ahead of a closed low over British Columbia. A disturbance rotating around this feature is initiating shower and thunderstorm development over the Rocky Mountain Front and Southwest Montana and this activity will eventually expand deeper into central and north-central locations by late this afternoon into the evening. Hi-res models continue to suggest that gusty winds up to 60 mph will be the most widespread impact from these storms, although small hail and brief heavy rain may accompany these storms. Areas along the Rocky Mountain Front and eastward toward the golden triangle will likely observe the greatest impacts as storms diminish in strength as they move east from there. Most activity should move out of the area by 6Z but some isolated shower/thunder activity can't be ruled out, especially along the Rocky Mountain Front. By Sunday, the aforementioned low pressure trough will move east over the Pacific Northwest, which will increase the southwest flow aloft over the region as a weak Pacific cold front traverses the region. Showers and thunderstorms may initiate much earlier than today, perhaps as early as the late morning. The NAM and HRRR, suggest that a wave of more moderate showers/thunder may develop ahead of the anticipated stronger activity as early as 13-15Z. Good moisture, steep mid-level lapse rate, wind shear should offer a good chance for severe storm development with large hail and damaging winds over the plains. Portions of the CWA will be under a marginal risk for excessive rainfall, so localized flooding due to heavy thunderstorm rains will be possible. Storms will encounter an increasingly more favorable thunderstorm environment as they move toward the east and northeast. One thing to keep in mind is that if shower activity begins earlier in the morning then some of the severe threat may be mitigated by convective contamination, especially for the central and western portion of the plains. As the Cooler air moves into the area behind the cold front late Sunday evening and overnight, the severe storm threat should diminish. Note, that scattered showers may linger into the overnight hours. Monday through Saturday... The Pacific Northwest trough will start to weaken as it moves more so into the Northern Rockies on Monday. Although the threat for severe weather will shift east of the area, more widespread rain showers with weak thunderstorms will persist through Monday into Monday night, as temperatures remain cooler than normal. The showers will decrease from the west Tuesday into Tuesday night as the low pressure trough moves east out onto the Great Plains, but temperatures will remain below normal one more day. A high pressure ridge will then build into the area on Wednesday, which should bring drier conditions with warmer than normal temperatures. This ridge will then be flattened somewhat by weak disturbances moving over Montana from the Pacific Ocean, leaving the area under a less stable westerly flow aloft with only slightly cooler temperatures. The disturbances will combine with afternoon/early evening instability to cause a few showers and thunderstorms to develop over the higher terrain and move out over the plains. Although this does not appear to be a pattern that would cause severe weather at this time, the situation will continue to be monitored. Coulston && .AVIATION... Updated 0535 PM MDT Sat Jul 6 2019 (00Z/Jul 7 TAF issuance) Showers and Thunderstorms will result in brief MVFR conditions though the evening before diminishing, especialy around GTF and HLN. Some of the storm could produce strong winds and large hail. Mainly VFR conditions are expected after midnight across the area. Additional showers and isolated thunderstorms will develop tomorrow morning, with a few strong to severe thunderstorms possible in the afternoon. Langlieb && .PRELIMINARY POINT TEMPS/POPS... GTF 53 79 52 73 / 60 50 50 40 CTB 49 73 47 69 / 50 40 40 30 HLN 52 80 52 75 / 50 50 50 70 BZN 50 81 52 74 / 30 50 50 80 WEY 41 78 44 68 / 20 20 30 80 DLN 48 76 48 71 / 40 50 40 80 HVR 55 82 54 75 / 30 50 40 30 LWT 51 80 51 68 / 30 60 70 60 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && http://www.weather.gov/greatfalls
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</html>The Great Falls radar (KTFX), 8 km away, was scanning. The volume nearest the first event began at 00:04 UTC.
3 hail, 2 thunderstorm wind, 1 flash flood. Local standard time, as filed.
KRTV reported a tree downed by thunderstorm winds at 1st Ave North and Park Drive.
A trained spotter provided a photo of a sizable tree limb snapped by thunderstorm wind gusts at the corner of 29th St North and Central Ave.
Meagher County DES reported quarter to half dollar sized hail.
Hail reported ranged from quarter to ping pong ball size. The spotter provided a photo of the hail stones.
Local media reported flash flooding in downtown along the 4th and 5th blocks of Central Ave. Flooding on one side of the road was about ankle deep, with flooding up to the car doors and some water reaching the store fronts. It was also reported that the underpass by the police station had cars submersed in flood water.
A trained spotter reported quarter sized hail and minor flooding along highway 2 near mile marker 2.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2019Every state in 2019This day in weather historyWarnings in Montana, July 2019
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 2026-09-30. Each event’s entry at NCEI: 837376, 837380, 837021, 837023, 844310, 837384.