Friday, April 8, 2011

Sunday Funday

Well, it took some convincing but I'm finally there - Sunday looks fun. People had been screaming about this day for the better part of a week already but I just didn't see it. The shape was just not there, if that makes any sense. However, I'm ready to call a fairly decent severe weather event for Sunday evening and the overnight hours for parts of the midwest.

I'm going to be back home in Champaign-Urbana until Sunday morning and am actually going to keep this discussion short so I can hit the road, but here's what I see.

The obvious cons to me are the lack of surface convergence along the dryline during the afternoon and early evening hours across the warm sector in central Iowa. Right ahead of the dry punch in central or eastern Iowa is where I would ideally plant myself right now, but I'm becoming concerned about day-time supercells in this chaseable region. I'd like to see a percentage of how many chase days I'm NOT concerned about potentially not getting daytime supercells in the days preceding them. Also, I would like to see the surface winds back a little more in the warm sector. Where we stand now, we would still probably be talking about supercells producing tornadoes on any storm that managed to erupt, but back the surface flow even slightly and I think we add wedge tornadoes to the menu on this one. The low will essentially bomb out right around sunset, which will likely force a backing of the surface winds in the warm sector. While this would greatly enhance the tornado threat (and associated LOCAL tornado threat in northern Illinois overnight) it may also mean the fun holds off until right around dark.

You just don't see a primed air mass like this ahead of such a dynamic system very often. Look at last week, we had a system that is all sorts of messed up dynamic wise combined with a shallow moisture plume returning to the target area literally just in time. Now, we've got a system that at 60 hours out looks like a system that is darn hard to complain about kinematically, with the MAJOR factor being the fact that a conducive warm and moist air mass will actually be in place the day before the event! Moisture is already surging northward at 60 hours out, and will be in place the afternoon before the event is even progged to happen. Middle 60s dew points have already reached central Missouri. So we've got the system with early spring dynamics, plus an unseasonably buoyant air mass in place well ahead of time. I think that is what interests me most.

I'm confused on what to do about the day though... but there is time. I'd love to scoot into eastern Iowa and bag a tornado or two, but in talking with Gilbert Sebenste moments ago he and I are both concerned about two separate tornado maxima. The first being along the dryline (a dryline in Iowa?!) and cold front during the late evening hours across central and eastern Iowa into southern Minnesota, and then hours later into the overnight a second tornado maxima may occur over northern Illinois, perhaps into southern Wisconsin and central Illinois where the low level jet absolutely howls after dark. That will greatly enhance the tornado threat in what may end up being a broken line of supercells by that point. In that case I would likely try what I can during daylight in Iowa, and then race home down Interstate 80/88 so that I can be back at the homestead before any tornadic supercell came knocking on my overnight doorstep.

So, I'll be handling the forecasting duties for NIU this weekend and have inherited a High Risk from Gilbert Sebenste, so after running through the forecast tomorrow morning I will try to nail down some more specifics on the ole blog. For now, I'm watching the eastern half of Iowa chase-wise, but keeping my third eye on the homestead for a potential duck and cover event.


Scott said...

You mean you won't be playing the warm front in northern Wisconsin with me? So sad!

Andrew Pritchard said...

Sure, and then we can take a dip in my frozen lake! I'd love to see how fast that thing thaws out this weekend! It was still frozen thick enough to walk on about 10 days ago.