FARGO — Scattered severe thunderstorms that could produce hail as large as 2 inches in diameter, wind gusts of up to 75 mph and flash flooding are expected to reach the Red River Valley late Tuesday night, July 7, and last into Wednesday morning.
The storms are expected to form in eastern Montana and western North Dakota around 8 p.m. Tuesday and move through the Bismarck area and on to eastern North Dakota and western Minnesota sometime after midnight. The system is forecast to move past the area and into eastern Minnesota sometime after dawn.
"A key to it is how this thing develops to our west," WDAY Chief Meteorologist John Wheeler said. "If it develops as a bunch of messy clusters of storms, that will be a very different outcome than what is most likely. The most likely event is that whatever forms out west eventually turns into a line of bowing echoes — lines that form a bow-shaped picture on radar — and those bows are often accompanied by heavy winds."
It is difficult to tell precisely which areas the storms could affect and how, Wheeler said. Some areas could see heavy winds and hail, while other places see nothing at all.
"It won't hit every location in the region," Wheeler said. "Some places won't get any rain at all and some will get a lot of rain. Some will get heavy winds and some won't get any at all ... With these midsummer weather events, the key to all of this is that we have uncertainty."
If heavy rains hit areas north of Fargo where the ground is already saturated, that presents a risk of flash flooding, WDAY meteorologist Andrew Whitmyer said.
National Weather Service meteorologist Brad Hopkins noted that the areas with the highest likelihood of heavy rainfall could be farther north.
"Right now, we're looking mostly at the northern part of our area," Hopkins said. "The entire forecast area is under threat. But the most likely places would be the northern part of North Dakota."
Wheeler said a secondary storm following up Wednesday morning's storm could hit some places in the Red River Valley on Wednesday afternoon or evening, but is unlikely to impact Fargo.
"There may be a second wave of storms (Wednesday) afternoon or evening that will form along a cold front that will have already passed through the Fargo area," he said. "But that could impact areas of western Minnesota, including Lakes Country."
Wheeler recommended that North Dakota and western Minnesota residents take safety precautions in case the storms impact their area.
"It would be a good night for people to make sure they have their StormTracker App and their phone set loud enough so that they can hear it and ... are awakened in the middle of the night if something bad is going on," he said.