UPDATE, 4:55 p.m.: The National Weather Service has emailed media and emergency management explaining that the false warnings sent out earlier today resulted from a system error:

...test weather warnings that were labeled as tests, but improperly coded as active warnings, were inadvertently distributed to subscribers of the weather wire and emergency management news wire. Though the messages were clearly labeled as a test, they should not have been distributed outside the agency.

From 4:10 p.m.: Three invalid severe weather warnings were inadvertently issued by the National Weather Service (NWS) Sterling, Va. office serving Washington, D.C. and Baltimore this afternoon. How these warnings reached the public is not yet known.

Although no severe weather was in the region, the following warnings were disseminated:

* a tornado warning for Fauquier county at 1:47 p.m. (until 2:30 p.m.)
* a severe thunderstorm warning for Baltimore, Carroll, Frederick, Howard, and Montgomery counties at 2:16 p.m. (until 2:45 p.m.)
* a tornado warning for Howard and Montgomery counties at 2:25 p.m. (until 3 p.m.)

In response to the illegitimate warnings, the following official statement was published on the NWS website at 2:40 p.m.

Reports of several severe thunderstorm and tornado warnings have been received by the national weather service office in sterling. There have been no warnings issued by this office...and absolutely no severe weather is occurring or expected. The National Weather Service is troubleshooting the issue at this time. To repeat...no warnings are in effect...and no severe weather or tornadic activity is occurring or expected.

Additionally, at 2:53 p.m., media and emergency management officials received the following email from Chris Strong, warning coordination meteorologist at the NWS-Sterling office:

As we currently know, at least 3 tornado warnings have been issued outside of the office for the mid Atlantic region. We are working furiously at the highest levels of our agency to find the source of these invalid alerts and stop them immediately. Please disregard any tornado warnings today in the mid Atlantic region. We will let you know the resolution of this as soon as possible.

It’s not clear if the NWS dissemination system was intentionally manipulated (e.g. hacked), or a system error occurred.