Wednesday evening storm leaves local communities without power

Just a bit of evidence ... This large branch from a tree just north of Waukon provided just a bit of evidence of the minimal structural damage done by the rare mid-December severe thunderstorm that blew through the Upper Midwest Wednesday, December 15. Although there was not a great deal of visible structural damage throughout the area, wind gusts between 60 and 70 miles per hour throughout the area did take their toll on area powerlines, leaving Alliant Energy customers in the town of Waukon without power for approximately four hours late Wednesday evening and again for a couple hours Thursday to aid repairs in surrounding areas. Standard photo by Joe Moses.

A rare December severe thunderstorm roared through Allamakee County and the surrounding area Wednesday evening, December 15, not necessarily causing a significant amount of visible damage but certainly having an impact on local electrical utilities. That impact was both immediate for most of that same night of the storm and then forced to return later the next day in an effort to remedy lingering effects.

Weather forecasters had been advising the Upper Midwest of a weather rarity for that mid-December day that would elevate temperatures into the 60s and ultimately bring strong winds and even stronger wind gusts. Those winds began to pick up throughout Wednesday and ultimately reached peak reports of 60 to 70 miles per hour at various locations in northeast Iowa.

Most of those peak wind reports occurred during the time a thin band of severe weather that included rain and lightning swept through the area, with the National Weather Service issuing a Severe Thunderstorm Warning for Allamakee County just before 7:30 p.m. Wednesday. Shortly after that warning was issued, most all of Waukon and the immediate surrounding area lost power as a result of winds that sent trees and limbs into power lines, toppled powerline poles in some locations or caused equipment at other sites to give way under the intense prolonged wind presence.

Melissa McCarville, Senior Communications Partner for Alliant Energy, said that the peak outage numbers resulting from the December 15 storm involved just over 4,000 Alliant Energy customers without power, nearly all of them within the town of Waukon. She noted that approximately 2,700 of those customers lost power immediately as a result of the severe thunderstorm and remained without power until crews could restore it, which happened around 11:45 that night. McCarville further shared that 1300 customers then lost power again for approximately one hour early Thursday morning from about 1-2 a.m. as further damage to power lines from sustained winds following the storm continued to take place.

After the initial power outage caused by the storm had been pretty much fully restored in the immediate Waukon area, Alliant issued notice late the following morning, Thursday, December 16, of another outage being planned for an approximate two-hour timeframe through mid-day Thursday. That planned outage was required in order for utility crews to repair electrical transmission lines feeding the Decorah and Cresco areas that were still without power through much of Thursday.

“Crews needed to switch to an alternate transmission feed in order to safely work on transmission lines damaged by the storm that were preventing Decorah and Cresco from receiving power,” McCarville explained. “It was unfortunate for our Waukon customers to have another outage to deal with, but it was necessary for the overall operations of the area.”

McCarville said that about 1400 Alliant customers in the Waukon area were impacted by Thursday’s planned outage, which took place from approximately 10:45 a.m. until 1:30 p.m. Repairs made during that outage allowed nearly all customers in the Decorah and Cresco area to have power fully restored by 2 p.m. Thursday, December 16.

McCarville said that by the end of the day Friday, December 17 most all Alliant customers in northeast Iowa had power fully restored, with some sporadic outages in harder hit north central Iowa still receiving attention. In all, Alliant Energy reported that approximately 100,000 customers had lost power as a result of the storm.

In contrast to the more focused area of impact in Waukon, residents of rural Allamakee County reported very little if any impact on their electrical service as a result of the storm. Jason Troendle, Director of Operations & Engineering for Allamakee-Clayton Electric Cooperative reported as many as 555 members of the cooperative lost power from the December 15 storm in the three-county northeast Iowa area of Allamakee, Clayton and Fayette counties served by Allamakee-Clayton Electric Cooperative.

Similar to what Alliant experienced, Troendle noted that the outages were mainly caused by trees in powerlines or pieces of equipment not able to withstand the combination of stronger wind gusts and continuing high wind speeds after the initial storm swept through. He further noted that all but a sporadic few areas of mostly unoccupied properties had been restored to full power by the cooperative’s crews by late Friday.

The storm had much more of a severe impact in north central Iowa, where five different tornadoes have been confirmed in Floyd, Chickasaw and Howard counties, in addition to six confirmed tornadoes in southeast Minnesota and four more in western Wisconsin. Although the Iowa tornadoes have been mostly classified as EF-0 or EF-1 with peak wind gusts of 85 up to 110 miles per hour, three of the four tornadoes in Wisconsin ramped up to EF-2 status and produced wind gusts of 120 miles per hour in Clark County, WI east of Eau Claire and well northeast of La Crosse, WI.

Additional information from the storm and related power outages was reported by Allamakee County Emergency Management Coordinator Corey Snitker and Allamakee County Engineer Brian Ridenour at the Monday, December 20 meeting of the Allamakee County Board of Supervisors. That coverage can be found on Page 4 of this edition of The Standard.