2012-04-15 FCST: IA, MN, IL, WI

[Tim Shriver]

I had been suspecting that the SPC would up the slight risk to a moderate risk if the models showed a good flow of moisture up into this area. This combined with some very strong shear we could see some large tornadoes and hail in the targeted area.
The question is now will we get enough day time heating. Models seem in good agreement, well as much as they can be.

We may not see real high CAPEs with dewpoints getting into only the 60's near ARX but the strong shear should more than make up for that. If the CAPEs do get higher than the forecasted 1200-1500 J/kg that will just add more flames to the fire.
The 70 kt LLJ will factor in to this later in the day and early evening as it noses its way into SW WI.

Temps and recovery are also a concern with the moring crapvection we are now having, but I think it will clear out enough toward
early to mid afternoon for some good heating getting temps into the mid to upper 70's. Some spots may even get into the 80's.

My starting point is going to be Dubuque IA. I can then move as needed.

Note: KARX radar is down for DP conversion. Could not of picked a better time.


Tim

 

[Dan Rupnow]

Amazing how much this system's movement has slowed down as opposed to what the NAM was advertising in earlier runs over the last few days. 11Z RUC shows the deepening surface low almost stationary all day in SW MN. As of now I am liking the WF/TP play in S MN. The favorably oriented SW to NE warm front would be in good position for any NE tracking storm to ride along it, and take advantage of the enhanced low level shear along it. Another thing I like about S MN is it is much better chasing terrain vs. WI, and that is even more important given the expected high storm motions today. Looking at morning sat. images, it appears that sufficient clearing will take place over this area to help build the needed instability. Moisture should not be a problem either, with upper 50s dews already in place over S MN, and that howling LLJ will do nothing but help pump more moisture into the entire warm sector today.

 

[Eric Matthews]

I couldn't agree more with you Daniel. The surface low has greatly slowed, diabatic heating should be higher than previous RUC's forecast, and MLCAPE is looking better. The slowed front has improved hodo's, which given the tremendous shear in place, was not needed.
I wish I made the drive today. Clear Lake Iowa is where I would stage with anticipated initiation around 4pm.

Edit... OK, now the new nam has really sped up again. looking much closer to Waterloo.

 

[rdale]

Edit... OK, now the new nam has really sped up again. looking much closer to Waterloo.

The 18Z NAM just started so not sure what you're seeing

In any case the 18Z soundings tell a dramatic story. Plenty of cap over most of the MDT area, and TAMDAR flights also picking that up too. With more clouds and blue skies, it's not looking good for Wisconsin.