A widespread power outage swept across Wyoming and western South Dakota on Thursday, leaving tens of thousands without electricity and causing significant disruptions across the region.

The blackout began around 12:45 p.m. when two major 500-kilovolt transmission lines near Medicine Bow, Wyoming, tripped offline. This triggered an abnormal voltage event that cascaded through the regional grid, leading to further outages. By mid-afternoon, approximately 95,000 customers were affected, with the majority located in central and northeastern Wyoming, including cities like Casper, Gillette, and Sheridan.

Utilities such as Rocky Mountain Power and Black Hills Energy reported extensive service interruptions. Rocky Mountain Power noted that over 60,000 customers experienced outages, while Black Hills Energy confirmed that the disruption extended into western South Dakota. Crews worked diligently to restore power, and by 4:30 p.m., service had been reinstated to about half of the affected customers. However, officials cautioned that the system remained unstable, and full restoration could take several more hours.

In a related incident, a fire ignited at the Dave Johnston coal-fired power plant near Glenrock, Wyoming, shortly after the outage commenced. State homeland security officials indicated that the blaze appeared to be a consequence of the grid failure rather than its cause. Local emergency teams responded promptly, and the fire was extinguished by mid-afternoon.

Communities across the region faced significant challenges due to the outage. In Casper, entire city grids went offline, prompting the closure of public facilities such as the Natrona County Library and the YMCA. After-school activities were canceled, and residents who rely on medical equipment were directed to designated facilities for assistance.

Utility companies urged residents to prepare for potential prolonged outages and to exercise caution during the restoration process. They emphasized the importance of staying informed through official channels and avoiding downed power lines.

This incident underscores the vulnerability of the regional power grid and highlights the need for continued investment in infrastructure resilience to prevent future widespread outages.