Weather forecasts like these can change substantially over the course of mere hours.
The massive windstorm that slapped America's east cheek over a distance of 700-plus miles on June 29 is not weather that most sane people want to experience twice. More than 20 dead, many from crushing injuries caused by falling trees; millions in property damage; a week without electric power in Washington, D.C. – derechos are just massive buzzkills.
Thus it was a little unsettling to see the phrase "widespread damaging wind event/derecho" mentioned in a government weather forecast issued Wednesday for Thursday afternoon. The Oklahoma-based Storm Prediction Center predicted a moderate risk of severe thunderstorms for a stretch of land from the Ohio Valley to the upper Mid-Atlantic to lower New England. The forecasters saw all-powerful winds as the major threat, although the National Weather Service did identify a "tornado risk in a narrow corridor from parts of New York State to southern New England."
The cities within the "moderate-risk" zone, meaning about a 45 percent chance of severe storms, as of the current forecast, included Cincinnati, Columbus, Cleveland, Pittsburgh, Scranton and New York. Click on any of those cities to travel to their respective National Weather Service offices.
Weather forecasts like these can change substantially over the course of mere hours. My suggestions for up-to-date national news on whether Thursday will feature rain-wrapped tornadoes or just plain old rain is to check those NWS city sites linked above, depending where you live, and also try these places: Storm Prediction Center, main NWS, Capital Weather Gang and the Weather Channel. If hail is flying, there are storm-chasing groups in Ohio, Pennsylvania and Massachusetts that will no doubt be sending out frequent updates.
For people who enjoy weather speculation, here's what Wednesday evening's storm-probability map looks like (courtesy of the SPC):
The derecho beat has really been full of meaty stories this year. If you happened to have missed the coverage of June's colossal smackdown, the D.C. office of the weather service has put up a great summary, which includes top wind speeds in several cities (82 m.p.h in Dayton, Ohio; 91 m.p.h. in Fort Wayne, Indiana!). Included is this radar playback of the sustained wind-blast mowing over eastern America. You can practically see a flock of toupées flying at the head of the gust front:
There's also this helpful map showing the frequency of derechos in different parts of the country. Sucks to live in northwest Arkansas:
Top image of a shelf cloud leading the June 29 derecho in LaPorte, Indiana, courtesy of Kevin Gould at NOAA.