Montana Sees Unusual August Flooding

The same strong low pressure system that brought 20–40mm to the Red River Valley last weekend brought significant rainfall to parts of central and eastern Montana. These extreme rainfall events in August are uncommon for Montana as strong systems usually stay well north with the polar jet stream and wildfires are typically the concern around this time of the year.

The deep low pressure system brought heavy rain (with a few breaks) to the region between August 21st and the 24th. Combined with abnormally high Precipitable Water values (PWAT) in the region, this made for high rainfall totals throughout the region. Storm total reports between 175mm and 200mm were not uncommon. Glasgow, MT saw around 145mm fall through the event (Aug. 21–24) which is four and a half times their monthly average rainfall for the whole month of August. In comparison to last year, they had less than a quarter of their monthly average rainfall by this time.

Many rivers in the regions quickly swelled up and spilled their banks including the Milk River which entered major flood stage near Glasgow on Monday. Mudslides also became a concern in the more mountainous regions. It appears that most of the damage due to the flooding occurred to roads and culverts, however some homes were damaged as well. Thankfully, there have been no reports of injuries. Crews are slowly working to rebuild the washed out roads.

More rain is impacting the region today, but nothing close to the magnitude of what was seen last weekend.