2013-06-11 FCST: SD/IA/IL

[James Gustina]

Seems like a sort of "small" event in the Midwest before the possible derecho day on Wednesday. I'm more interested in the Illinois component of this forecast but it looks like Iowa and South Dakota have the best shot at daytime severe storms. Northwesterly H5s coupled with extremely high instability (best part of June) always tend to be nice days out there, but the degree of capping is the only thing that gives me pause. Forcing won't be particularly strong over most of Iowa and Illinois, add in very weak shear and there's an increased likelihood this ends up being a clustered mess.

Still, northwesterly flow, MLCAPE on the order of 4000 j/kg+ with a frontal boundary pushing north into the early evening still gives me enough confidence to at least head out and see if I can get some lightning photos after dark.

 

[chrisbray]

I agree, forecast soundings show steep low level lapse rates and high instability. GFS has the higher wind shear values farther south, so who knows, maybe we will get a nice mix between the two models and get some lovely storms to photograph

 

[James Gustina]

Honestly, any boundary or localized convergence zone in Illinois tomorrow could shoot off a nice storm, but that cap looks a bit thermonuclear. Might get a mesoscale accident like today in southern Kentucky, but I'm not overly optimistic right now. If surface temps get higher than forecast, along with maybe a smidge of enhanced shear over north-central IL, there's a shot for daytime cells at least.

 

[chrisbray]

Cap will be an issue, but we will see. WRF and RAP like to break out a big cell or two tracking southeast across northern Illinois, probably because the RAP brings an area of 50 kt shear across the region at that time.

I'm definitely still keeping an eye on this, as well as tomorrow