STORM2K

While the actual word "derecho" has not been applied to the possible events of tonight, the forecasts and wording used by the NWS and SPC seem to suggest a long, massive, thunderstorm wind event affecting southern Iowa and northern Missouri.

I'm no expert, but what would all this information lead you to believe?

http://spc.noaa.gov/products/outlook/pwo.html
http://spc.noaa.gov/products/outlook/day1otlk.html
http://www.crh.noaa.gov/showsigwx.php?warnzone=MOZ025&warncounty=MOC121&local_place1=Macon&product1=Hazardous+Weather+Outlook

Of particular note:

NWS wrote:THE PRIMARY SEVERE THREATS WILL BE
LARGE HAIL...GOLFBALL SIZE OR LARGER...DAMAGING WINDS...TORRENTIAL
RAINS AND FREQUENT LIGHTNING. AS THE THUNDERSTORMS INTERACT WITH EACH
OTHER THE POTENTIAL EXISTS FOR A COMPLEX OF STORMS TO FORM WHICH
COULD EVOLVE INTO A WIDESPREAD WIND STORM EVENT.

So yeah, is this a potential derecho, or a slightly smaller animal with rather large teeth? Either way, it sounds serious.

I mentioned this possibility in a previous thread...however, PurdueWx said that while not out of the question, the wind field wouldn't be large enough to support a full-blown derecho.

I think though, at the very least, with the instability in the region and plenty of deep-layer sheer, one heck of a squall line will probably develop and push through northern Missouri and southern/central Iowa later this evening. Probably will see some bow echos and large hail in these storms, but due to pretty weak helicity, not much in the way of tornadoes (isolated at best).

Should be active at the very least.