Sioux Falls NWS labels Thursday's strong winds a 'derecho,' with damages similar to a tornado
The Sioux Falls National Weather Service is calling Thursday's damaging straight-lined wind event in southeastern South Dakota a "derecho," or a "long-lived wind storm with a line of quick-moving thunderstorms."
"This (was) not a tornado," meteorologist-in-charge Todd Heitkamp said of the damage experienced in southeastern South Dakota.
Most tornadoes in the country form on the backside of a thunderstorm. Yesterday evening, Heitkamp said Sioux Falls experienced the "front side of the storm."
"You couldn't see your nose in front of you when that storm hit," Heitkamp said.
NWS issues first 'particularly dangerous situation' warning since 2015
The NWS said winds 70-100 mph winds were measured in large swaths of southeastern South Dakota.
Those winds were part of the same storm complex but were two separate storms: one formed the "tornado" seen in Castlewood, where everything was "right, nice and clear"; and the others did not, where Sioux Falls witnessed its strong winds, Heitkamp said.
"(Most of the damage we witnessed) around here was reminiscent of high end EF-0 tornado or a low end EF-0 tornado," Heitkamp said.
The storms started in north-central Nebraska and quickly moved northeast into South Dakota.
NWS issued its first severe thunderstorm warning for Sioux Falls at 4:40 p.m., alerting of potential 80 to 100 mph winds within the warning. That gave the city of Sioux Falls and surrounding communities 22 minutes of lead time to take shelter.
The watch was issued with a description of a "particularly dangerous situation." The last time NWS issued a PDS severe thunderstorm watch was 2015. The one before that was 2008.
"Those terms are not used lightly by the Storm Prediction Center out in Norman, Oklahoma," said Heitkamp.
According to a tweet by NWS Sioux Falls, the weather service said this year was the 3rd highest to date for warning totals since 1986, behind 2004 (106), 2007 (114) and 2012 (120). NWS has issued a total of 106 severe thunderstorm and tornado warnings.
Pushed up topsoil created dark dust storm in Sioux Falls
A huge dust cloud ominously led the storm into the region, and once it hit, visibility was poor.
When the wind hits the ground, topsoil this time of year is exposed, Heitkamp said.
"And so it pushes (the topsoil) up, and that's what gave us the dark appearance as it was approaching the city of Sioux Falls," he said.
Derechos can pack lethal gusts in excess of 100 mph — hurricane strength — across a front stretching for many miles, and last for hours.
On Friday, Heitkamp didn't want to worry about labeling the storm with technical meteorological terms he said most people don't understand, but the last one Sioux Falls has experienced recently was a couple years ago, and it went through Iowa, into Illinois and Michigan.
"That storm there had comparable winds to what we experienced last night," he said.
There's no comparison to what Sioux Falls saw on Thursday because the storms "fell apart as it went into central Minnesota."