A subtle shortwave trough drifted southeastward over north-central and southwest Montana during the afternoon and early evening of May 30th. Isolated showers and thunderstorms developed via daytime heating of higher terrain amidst weak to moderate instability and weak vertical wind shear.
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 subtle shortwave trough drifted southeastward over north-central and southwest Montana during the afternoon and early evening of May 30th. Isolated showers and thunderstorms developed via daytime heating of higher terrain amidst weak to moderate instability and weak vertical wind shear. One thunderstorm managed to produce damaging wind gusts near Helena.
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 30, 1:37 PM MST, 1 hour 28 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 237 PM MDT Thu May 30 2019 .SYNOPSIS... Scattered showers and thunderstorms are possible Thursday and Friday afternoon. A weak frontal boundary will slow the recent warming trend on Friday. Warm and dry conditions return for the weekend as temperatures climb back above average. && .DISCUSSION... Rest of this Afternoon through Friday Night...Cold front aloft continues to move south across central Montana this afternoon, and is serving as the trigger for more widespread shower and thunderstorm development over northern and central Lewis and Clark County and southwestern Teton County. The remnants of this front will stall along the mountains-plains interface through Friday, with increasing moisture and instability behind the front helping to trigger additional showers and thunderstorms which will be most concentrated along and near where flooding impacted the Rocky Mountain Front earlier this week. Slow-moving showers and thunderstorms can be expected across much of the rest of the area except for far northeast sections where conditions will remain largely dry. With weak flow, weak to moderate instability any thunderstorms should remain below severe levels, with heavy rain, small hail, frequent lightning, and gusty winds the primary threats. This Weekend through Thursday...Upper-level ridging strengthens through the weekend. Although a few mainly mountain thundershowers can't be ruled out, most areas will enjoy warm, breezy and dry conditions, with the warmest temperatures of the year so far. A weak cold front will knock down the temperatures a bit on Tuesday but may bring breezy an dry conditions to the plains resulting in elevated fire weather conditions. Fair weather continues with seasonal temperatures under a dry zonal flow aloft Wednesday and Thursday. && .AVIATION... Updated 1040 AM MDT Thu May 30 2019 (18Z TAFs) Mainly VFR conditions are expected through the forecast period, with some possible brief exceptions to MVFR or IFR from slow- moving showers and thunderstorms west of KHVR and KLWT, and mostly focused along the Rocky Mountain Front where mtn obscurations will be possible at times especially from this evening through the overnight. Sky cover will trend upward through the period, and so will shower/thunderstorm chances area- wide. Wildfire smoke aloft from large wildfires in Alberta may bring hazy skies at times. && .HYDROLOGY... Runoff from the heavy rain and snowmelt last weekend has moved away from the Rocky Mountain Front as river level crests move further downstream. All Flood Warnings have been cancelled except for the Teton River between Dutton and Loma. Any increase or decrease in releases from Gibson will have a significant impact on water levels on the Sun River, so river levels may remain near or at minor flood stage for several days. Warmer temperatures will continue to produce snowmelt runoff, so water levels will need to be monitored for changes. The big unknown remains slow-moving shower and thunderstorm potential and how much that impacts the main-stem rivers over the next few days. && .PRELIMINARY POINT TEMPS/POPS... GTF 52 70 50 78 / 20 40 10 10 CTB 50 71 48 78 / 40 30 10 10 HLN 51 72 49 79 / 20 60 20 30 BZN 46 72 45 77 / 20 60 10 20 WEY 36 66 36 68 / 30 30 30 30 DLN 44 72 44 74 / 20 50 30 50 HVR 53 77 51 82 / 10 20 10 0 LWT 49 68 47 75 / 10 60 10 50 && .TFX WATCHES/WARNINGS/ADVISORIES... Flood Watch from 6 PM MDT this evening through Saturday morning Cascade...Central and Southern Lewis and Clark...Eastern Glacier...Eastern Pondera...Eastern Teton...Northern Rocky Mountain Front...Southern Rocky Mountain Front. Flood Warning remains in effect for the Teton River from Dutton in eastern Teton County to near Loma in Choteau County. && http://www.weather.gov/greatfalls
Special Weather Statement National Weather Service Great Falls MT 242 PM MDT Thu May 30 2019 MTZ048-302145- Southern Rocky Mountain Front- 242 PM MDT Thu May 30 2019 ...A STRONG THUNDERSTORM WILL AFFECT CENTRAL LEWIS AND CLARK COUNTY... At 239 PM MDT, a strong thunderstorm was located near Augusta, or 29 miles southwest of Choteau, moving east at 5 mph. Winds in excess of 30 mph and pea size hail are possible with this storm. Locations impacted include... Nilan Reservoir. If outdoors, consider seeking shelter inside a building. Torrential rainfall is also occurring with this storm, and may cause localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. To report severe weather, contact your nearest law enforcement agency. They can relay your report to the National Weather Service office in Great Falls. LAT...LON 4745 11271 4736 11267 4735 11233 4759 11249 TIME...MOT...LOC 2039Z 254DEG 5KT 4744 11251 TP
Special Weather Statement National Weather Service Great Falls MT 312 PM MDT Thu May 30 2019 MTZ012-014-048-302145- Cascade-Southern Rocky Mountain Front-Central and Southern Lewis and Clark- 312 PM MDT Thu May 30 2019 ...A STRONG THUNDERSTORM WILL AFFECT CENTRAL LEWIS AND CLARK... SOUTHERN TETON AND WESTERN CASCADE COUNTIES... At 311 PM MDT, a strong thunderstorm was located near Augusta, or 25 miles south of Choteau, moving southeast at 10 mph. Winds in excess of 30 mph and pea size hail are possible with this storm. Locations impacted include... Augusta. This includes the following highways... Highway 200 between mile markers 114 and 118. Highway 287 between mile markers 21 and 40. If outdoors, consider seeking shelter inside a building. Torrential rainfall is also occurring with this storm, and may cause localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. To report severe weather, contact your nearest law enforcement agency. They can relay your report to the National Weather Service office in Great Falls. LAT...LON 4748 11246 4756 11223 4736 11199 4723 11234 TIME...MOT...LOC 2111Z 331DEG 10KT 4746 11230 TP
Special Weather Statement
National Weather Service Great Falls MT
351 PM MDT Thu May 30 2019
MTZ012-302245-
Cascade-
351 PM MDT Thu May 30 2019
...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN CASCADE COUNTY...
At 350 PM MDT, a strong thunderstorm was located near Fort Shaw, or
21 miles north of Cascade, moving south at 5 mph.
Winds in excess of 30 mph and pea size hail are possible with this
storm.
Locations impacted include...
Fort Shaw, Fort Shaw, Simms and Sun River.
This includes the following highways...
Highway 200 between mile markers 128 and 139.
Highway 89 between mile markers 9 and 19, and near mile marker 8.
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in Great Falls.
LAT...LON 4750 11192 4761 11192 4761 11173 4750 11166
4745 11193 4750 11194
TIME...MOT...LOC 2150Z 351DEG 5KT 4756 11185
TPSpecial Weather Statement
National Weather Service Great Falls MT
357 PM MDT Thu May 30 2019
MTZ012-302230-
Cascade-
357 PM MDT Thu May 30 2019
...A STRONG THUNDERSTORM WILL AFFECT WEST CENTRAL CASCADE COUNTY...
At 357 PM MDT, a strong thunderstorm was located 7 miles northwest of
Cascade, moving south at 5 mph.
Winds in excess of 30 mph and pea size hail are possible with this
storm.
Locations impacted include...
Cascade and Tower Rock State Park.
This includes Interstate 15 between mile markers 247 and 259.
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in Great Falls.
LAT...LON 4739 11201 4745 11166 4725 11166 4716 11174
4721 11202 4725 11201
TIME...MOT...LOC 2157Z 011DEG 5KT 4734 11183
TPSpecial Weather Statement National Weather Service Great Falls MT 401 PM MDT Thu May 30 2019 MTZ014-302300- Central and Southern Lewis and Clark- 401 PM MDT Thu May 30 2019 ...A STRONG THUNDERSTORM WILL AFFECT SOUTH CENTRAL LEWIS AND CLARK COUNTY... At 400 PM MDT, a strong thunderstorm was located 16 miles southwest of Wolf Creek, or 17 miles northwest of Helena, moving east at 5 mph. Winds in excess of 30 mph and pea size hail are possible with this storm. Locations impacted include... Marysville and Canyon Creek. If outdoors, consider seeking shelter inside a building. Torrential rainfall is also occurring with this storm, and may cause localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. To report severe weather, contact your nearest law enforcement agency. They can relay your report to the National Weather Service office in Great Falls. LAT...LON 4680 11238 4671 11235 4667 11206 4695 11222 TIME...MOT...LOC 2200Z 251DEG 6KT 4680 11224 TP
Special Weather Statement National Weather Service Great Falls MT 403 PM MDT Thu May 30 2019 MTZ012-302230- Cascade- 403 PM MDT Thu May 30 2019 ...A STRONG THUNDERSTORM WILL AFFECT CENTRAL CASCADE COUNTY... At 403 PM MDT, a strong thunderstorm was located 7 miles south of Great Falls, moving southeast at 5 mph. Winds in excess of 30 mph and pea size hail are possible with this storm. Locations impacted include... Stockett, Eden and Sand Coulee. If outdoors, consider seeking shelter inside a building. Torrential rainfall is also occurring with this storm, and may cause localized flooding. Do not drive your vehicle through flooded roadways. LAT...LON 4741 11140 4746 11128 4734 11105 4721 11133 TIME...MOT...LOC 2203Z 326DEG 5KT 4739 11130 Kredensor
The Great Falls radar (KTFX), 99 km away, was scanning. The volume nearest the first event began at 22:06 UTC.
1 thunderstorm wind. Local standard time, as filed.
Public reported a shed was damaged and displaced 10-yards by outflow. Photos were provided.
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, May 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 2026-09-24. Each event’s entry at NCEI: 818960.