Tanja Fransen, Meteorologist-in-Charge at the NOAA/NWS office in Glasgow, has released preliminary reports on the storm systems that moved through this area Tuesday through Thursday. This report was not released prior to the Sunday edition of the Sidney Herald going to press and is therefore only available online at this point.
According to the report, Tuesday’s storms produced some large hail at first with winds picking up as the storm tracked north.
“The event started with thunderstorms kicking off north of I-94 in Dawson and Wibaux Counties with storms moving in a northerly direction. The largest reports of hail were four inches in diameter, nine miles east of Glendive, and baseball size hail (2.75”) 15 miles north of Wibaux,” the report stated. Quarter to golf ball sized hail was also reported in Wibaux, Dawson, Richland and Roosevelt Counties.
The report then addressed the downburst winds in Fairview. “As the storm moved north, downburst winds caused minor to moderate damage to buildings in the Fairview area, uprooted some large pine trees and damaged large branches on other trees. Strong to severe thunderstorm winds of 55 to nearly 80 mph were reported.”
The report then said additional storms started forming in Garfield, Valley and Phillips Counties, eventually extending into Western Roosevelt County. Winds were in the 40 to 60 mph range with a report of golf ball size hail at the Hell Creek Marina in northern Garfield County.
According to Fransen, storms trained (followed the same path over and over) in western Roosevelt County, leading to flash flooding as water came up and over US Highway 2 about five miles west of Wolf Point as well as Highway 13 North of Wolf Point.
Some residents stated they had never seen water that high in over 50-85 years of being in the region.
Rainfall estimates and spotter reports indicated the totals were 3-6 inches in under 90 minutes. Although the area is in a D2/D3 moderate to extreme drought, the soils could not handle that much water in a short time.
According to the report, the two biggest impacts on this day was the hail in Dawson/Wibaux Counties and the flash flooding in western Roosevelt County over highways.
The report then moves to Thursday’s weather, stating it was much more significant.
The report stated warm, moist air had been building in eastern Montana and a cold front was coming in from the west, causing thunderstorms to form in the Yellowstone River Valley from Wibaux to Sidney and then moving in a NNE direction into North Dakota.
The storms had rotation in them, triggering tornado warnings along the Montana and North Dakota border numerous times.
According to Fransen, “As far as could be ascertained from reports from storm chasers, weather spotters, the public and DES Coordinators, the first actual tornado most likely actually occurred in North Dakota but could easily be seen from Montana. No reports of damage were received from tornadoes in Montana or North Dakota.”
Further north, storms moved into northern Roosevelt/Daniels and Sheridan County. Some isolated damage occurred from what on video looks to be a gustnado. In reviewing the radar data, there were no storms in the Flaxville area when this damage occurred.
Thursday evenings weather started in the west with thunderstorms in south-central and central Montana drifting northward.
“While they initially weren’t very significant, as they moved northeastward, the storms moved into more unstable air and a cold front coming in from the west helped cause them to increase in intensity by early evening,” said the report.
These storms moved across northwest Prairie County all the way through the Sidney/Fairview and Bainville areas several hours later. They had hail as large as three inches in diameter and winds from 70 to 90 mph measured, with a damage survey showing support for up to 115 mph in the area about six miles northwest of Sidney.
The high winds caused damage to homes and buildings, took down 75 year old spruce trees, and snapped approximately 1,000 power poles in Terry, McCone, Dawson, Prairie and Williams Counties. These poles were owned by either McCone Electric, Lower Yellowstone Rural Electric or DOE/Western Area Power Administration.
This is a preliminary report and officals at the NOAA/NWS are still evaluating the storms.