Ominous clouds caused a stir in Cass County on Friday afternoon when sightings of funnels prompted emergency sirens to sound across the Fargo-Moorhead area.
The National Weather Service said the system that caused all the worry was not severe enough to generate tornadoes, and none were reported Friday afternoon.
Warning sirens were sounded at 2:33 p.m. in the cities of West Fargo, Fargo, Horace, Moorhead and Dilworth after a law enforcement agency notified the Red River Regional Dispatch Center that funnel activity was observed west of Fargo.
The warnings did not dramatically change the school day for West Fargo students, who were let out of class at the usual time, school officials said.
Mary Phillippi, the shift supervisor at the dispatch center Friday afternoon, said alarms are sounded when the National Weather Service issues a tornado warning for any community covered by Red River Regional Dispatch Center, or when a trained weather observer or law enforcement officer has spotted a tornado and requests activation.
In nontornado situations, a fire department commander can request the sirens in cases involving hazardous materials or the Cass or Clay County emergency director can request alarm activation, Phillippi said.
Mark Ewens, data manager for the weather service in Grand Forks, N.D., said it was prudent to sound the sirens Friday, even though no tornadoes were reported.
He said the funnels sighted Friday are known as cold-air funnels, which form from cold, humid air masses and rarely reach the ground. When they do, they create weak tornadoes, Ewens said.
Powerful tornadoes are created by warm, humid air masses, which are very unstable and lead to severe storms, he said.
Ewens said cold-air funnels are relatively common during the summer months, but he added the funnels sighted Friday may have been the first in the Fargo-Moorhead area this year.