The moderate risk for severe weather that I noted yesterday was downgraded to a slight risk this morning, though there are still a few reports of significant severe weather, namely enormous hail up to 4 inches in diameter in eastern Kentucky. Wind damage has been widespread through the region as well. Take a look at the severe weather that has been observed to this point.

Perception bias leads people to believe that there is some sort of shield that protects them from severe weather (the so-called Arch Effect in St. Louis, for example) but it’s actually a matter of odds. Major cities don’t get hit as often because they don’t take up as much space, so it FEELS like they are safer, though the threat is just as real. Of course (and the day is definitely long from being done) it’s getting harder to believe that West Virginia doesn’t have a dome around it.
(As I say this, there are severe storms east of Lexington, Kentucky with a chance of grazing the state and a line developing from just northwest of Columbus, Ohio to north of Louisville, Kentucky, so the day isn’t over yet, but by golly it looks like West Virginia is going to dodge another bullet.

An active upper level trough is digging it’s way into the Ohio Valley, and the Storm Prediction Center has issued a moderate risk for portions of the Ohio Valley, particularly West Virginia and much of eastern Ohio, primarily because of the threat for significant severe weather (hurricane strength wind, 2 inch hail or tornadoes EF2 or stronger). Before I continue, here is the outlook as the SPC has foreseen.

As you may have noticed, I said the threat for a severe weather outbreak is rare in West Virginia (though not unheard of). Take a look at the following climatology (via the SPC) for this time of year, showing the frequency of severe tornadoes, wind and hail, and note that West Virginia has a lower risk than everywhere around them.

In particular, look at this, the climatology for significant wind this time of year in West Virginia. West Virginia functions as the hole in a donut!

Given that it’s so unusual to see terrible thunderstorms in this part of the world, this moderate risk wasn’t issued lightly. Take care tomorrow in the Mountaineer State!

As Ryan mentioned, we’ve been analyzing the forecast and verification of a system that would affect the Northern Plains over the last couple of days, which was kind of all over the place but eventually honed in on during the morning of the event. The NWS put together a pretty neat graphical overview of the event, as taken from radar images of the storm from start to finish as it went from central North Dakota through northern Minnesota:

As you can see, the main corridor of severe wind reports followed the northern portion of the derecho as it marched though North Dakota. The southern end got a bit more intense as it moved through Minnesota, and as you can tell, the atmosphere was very capped over SD and southern MN. The southern end made very little progression to the south, while there was plenty of activity on the northern end even away from the main line of storms. So while the forecast took a couple of days to really nail down, and was fairly elusive in doing so until the day of, the SPC got it pretty much dead on, and the radar images prove it as well.