Sunday's storms produced golf ball-sized hail and much needed rain for parts of the area
Two rounds of storms moved through the Red River Valley Sunday, July 10.
FARGO — Two rounds of thunderstorms moved through the region on Sunday: the first during the morning hours, and the second during the early afternoon. The first line of storms brought with it some gusty winds around 60 mph to parts of the region, while the second round of thunderstorms was more noted for the hail that it produced around the south Fargo area.
The first round of thunderstorms was a nighttime thunderstorm complex which originated in eastern Montana on Saturday evening and then tracked through North Dakota during the overnight hours and into the early morning hours on Sunday. These storms brought winds gusting upwards of 70 mph across parts of western and central North Dakota during the overnight hours. This group of thunderstorms moved across the Red River at around 8 a.m. and then continued eastwards into western Minnesota before eventually weakening west of Duluth around noon.
In its wake, the first round of thunderstorms left behind an increased amount of moisture in the region. It also left behind cooler air in the low levels of the atmosphere, which prevented additional activity from developing. This temporary pause allowed for the atmosphere to continue to destabilize. Meanwhile, an area of low pressure around Aberdeen, South Dakota was beginning to move towards Fargo. Accompanying this low pressure was a warm front which generally remained near the North Dakota/South Dakota border, and a cold front which was pushing its way into eastern South Dakota. This resulted in the air converging over our region as the low pressure neared, and this provided the forcing mechanism for the second round of thunderstorms to develop.
Temperatures at the surface had recovered back into the upper-70s and even into the lower-80s around the Fargo area. Dew point values were sitting around 70°. Mid level and upper level temperatures began to drop a bit, and given the already unstable air mass in place, once this happened, the warmer air at the surface began to rise — quickly.
At 11:40 a.m. on Sunday, it was fairly quiet in our region, though some might have noted an increase in clouds near Interstate 94. These clouds quickly grew, and moments later, the first lightning strikes and raindrops were falling. The quick development of the thunderstorms also showed how strong the updrafts of the thunderstorm were. These updrafts continued to grow, upwards of 45,000 ft. By doing so, they forced water droplets above the freezing level (likely around 15,000 ft), causing the water to eventually freeze and leading to the development of hail. By 12:20 p.m., most of the I-94/US-10 area was experiencing these strong thunderstorms.
The line of storms began to drift southeastwards, with the western section beginning to approach Wahpeton. However, the storms in this area began to weaken noticeably. The likely reasoning for this was that the rain cooled air from the storms moving out of Detroit Lakes began to cut off the inflow for the storms approaching Wahpeton. By 2:30 p.m., most of the remaining storms had left the region.
Penny-sized hail fell across the south Fargo area around 12:30 p.m. Northern Ransom County saw hail upwards of an inch in diameter from their section of the storm. The largest hail reports came in from Becker County, Minnesota, where hail upwards of 1.5 inches in diameter fell. Storm reports show that the hail from these storms was generally confined to a narrow area spanning roughly from northern Ransom County through south Fargo, and into southern Becker County, Minnesota. In addition, these storms also brought heavy rains into the region, with some places receiving around an inch of rain between the two rounds of storms.