6-18-2021 severe threat

Good afternoon guys! 

It has been awhile since a good severe weather day in Illinois! Well, the next three days are all going to be worth watching, especially today (Friday) and Sunday!

I will mostly discuss today's threat and briefly touch on tomorrow's and Sunday's. I will go more details on those on the day of! 

So, even just 6-12 hours before this severe weather setup on folds, the HRRR and the NAM are disagreeing with each other like they always do and this is making things complicated. Both agree that there will be severe storms, and for IL both do agree that there will be some severe storms that will fire after dark in central IL. But, the main action this afternoon across Indiana and Ohio is what is being questioned. The NAM has boldly stuck with this line forming around 3/4 in NE Indiana and NW Ohio and charging south to southeast, this being mostly a damaging wind threat but Hail and a couple Tornadoes are possible as well. 

The HRRR is is showing little development until very late, near sunset further south with not as significant as a threat. Although the HRRR was more correct with yesterday's storms, I will guess the NAM to be more in the right today as with what I am seeing with the ingredients as well as there are already a couple storms forming just north of me here in East-central IL which means that the atmosphere is already primed up. 

TIMING: Eastern Indiana (into central) and much of the western half of Ohio, be on guard from 3-7 this afternoon as that line segment heads south. If the HRRR will be correct, then there will be little development until 6/7pm tonight.

FOR ILLINOIS: most storms will not initiate until near or after dark due to the front stalling across southern Iowa and Northern IL, with very high instability (3,000-4,000+) among other factors, but develop late due to an enhancement of South to Southwest winds in Iowa which will interact more with the front and cause storms to fire after dark (9/10ish for the first storms).

Due to high instability and high lapse rates, HAIL will be the greatest outmost concern with these (along with damaging wind), which could produce large to very large hail within a small corridor from Southern Iowa and Central IL. These storms will mostly start off in Iowa but expect by midnight a line of storms from Southern Iowa to West-central Indiana, most storms within this line being strong to severe. This threat will terminate by 3/4am hopefully. A tornado or two is also not completely ruled out but wind shear will not be as strong as it is across the IN/OH region this afternoon.

So today should be watched and also look at the radar before you plan and going anywhere in each region and the specified times above.

NAM at 5pm

NAM at 12am

Below I have my thoughts on the outlooks from Saturday and Sunday. I will have many more details in the next two days! These are subject to change. Stay tuned!

NAM 7pm Sunday