An unusually long and far-reaching communications outage hobbled the National Weather Service just as deadly severe thunderstorms were tearing across the Midwest and Ohio Valley on Tuesday evening.

The outage is more evidence of the long-running IT infrastructure challenges facing the agency, which is part of the National Oceanic and Atmospheric Administration.

The outage meant that severe thunderstorm, flash flood and tornado warnings were significantly delayed in reaching the public, except via NOAA Weather Radio, according to the NWS.

According to a person familiar with the matter, the root cause of the issue, which lasted from 6 p.m. ET to 7:14 p.m. ET, was a software upgrade being made to the main computer system that forecasters use to monitor weather conditions and issue watches and warnings, known as AWIPS.

This software system is antiquated, and NWS is working to update and replace it with a new cloud-based architecture by 2028, the person said. They were granted anonymity because they were not authorized to discuss the issue.