Latest On Heat, Humidity Now & Storm Potential For Today-Tomorrow MorningJune 17th, 2014 at 3:24 pm by Chad Evans under Chad's WLFI Weather Blog
Comma head of derecho & its line damaging winds are on-going in Ontario!
We area boiling pot on a stove with a lid today! Winds continue to gust 35-40 mph across the viewing area. They are sustained at 25-31 mph.
Highest measured gust so far has been 42 mph at Fowler.
With surface CAPE as high 4500 J/kg & decent shear, the outflow boundary is continuing to be monitored. Cap is in place, but has recently weakened a hair near it.
Again, if any isolated storm can pop through the cap on that boundary, it would do so very quickly & would go severe very quickly with large hail/downburst potential.
There is still uncertainty, as cap could re-strengthen.
Another thing to watch is storm development in northwest Illinois/northeast Iowa/southwest Wisconsin where high CAPE/good shear exists. There, storm cluster will likely explode this evening & race east/southeast. That area is capped, too, but shortwave will weaken cap & allow storm explosion this evening.
This should quickly evolve into a bow of damaging straight-line winds, though given the CAPE in Iowa area large hail may occur generally in the first 2-3 hours of the MCS’ evolution. Flooding issues are possible in that area that was hit just last night-early this morning.
Our latest Hi-Res Futurecast run shows a matured bow of storms possible at the Kankakee River at 4:19 a.m. & the line over Newton, Jasper, Pulaski, Fulton at 6 a.m. That is as far south as this model brings the line.
However, I would be on guard along & north of U.S. 24 & have it as a note as far south as Lafayette.