NBC Nightly News with Brian Williams

Tornado watch issued for central and eastern Oklahoma, including Moore, Oklahoma City and Tulsa until 10pm CDT - via The Weather Channel

MORE: Ricin letter sent to President Obama similar to those sent to NYC Mayor Michael Bloomberg »

BREAKING NEWS: Ricin letter mailed to President Obama containing threats similar to those sent to NYC Mayor Bloomberg, sources tell NBC News. Letter was intercepted by U.S. Secret Service.

Rain, floods & more tornadoes set for storm-battered central U.S. »

BREAKING NEWS: Letters sent to NYC Mayor Michael Bloomberg preliminarily test positive for ricin; letters referenced debate on guns, NYPD says

Severe weather forecast for tomorrow through Friday - via The Weather Channel

Brian Williams interviews 6 amputee survivors of the Boston Marathon bombing. Interview airs Friday.

BREAKING NEWS: Tropical Storm Barbara strengthens to hurricane status as it nears the coast of Mexico: 75 mph winds, moving NNE at 10 mph; first hurricane of the 2013 season »

Today’s severe weather forecast via The Weather Channel

Boston Marathon bombing victim attends senior prom, voted prom queen

Story/video: http://nbcnews.to/146tJ9s

Just in: 4.6-magnitude earthquake 12 miles west of Santa Barbara, CA

VIDEO: NBC affiliate KAMR-NBC4 broadcasts from bathroom during tornado warning »

Congresswoman Michele Bachmann (R-MN) won't seek re-election next year »

Boston Marathon bombing survivor Jeff Bauman throwing out the first pitch tonight at Fenway. (via @Boston_Police)

Fire burning after freight train derailment in Baltimore County, MD