ILSNOW Posted June 13, 2022 Share Posted June 13, 2022 Chicago NWS .MESOSCALE DISCUSSION... Issued at 1102 AM CDT Mon Jun 13 2022 Concerns continue to focus on the best timing of possible significant severe thunderstorms with heavy rainfall this afternoon into early this evening. A couple of MCV`s, with ongoing convection are present to our west-northwest. The first is located over northeastern IA, with another one farther northwest into MN. Concerns are that the extensive convection over southern MN into northeastern IA in association with these features will mature into one or two east- southeastward forward propagating MCS`s this afternoon into early evening as surface warm front (and the strongly unstable airmass to its south) shifts northward into parts of northern IL and northwestern IN. The airmass within and near the warm sector is already extremely unstable thanks to hot and humid surface conditions (temperatures into the 80s amidst dew points well into the 70s). In fact, MUCAPE was already calculated at nearly 6,000 J/KG on the 12z KILX RAOB, with mid-level lapse rates in excess of 8.5C per km in the EML. The instability gradient is expected to set up right over northern IL and southern WI into Lower Michigan this afternoon, and will essentially offer the pathway for any forward propagating MCS`s this afternoon. However, exactly where any MCS will propagate remains uncertain and will be tied to *when* the system develops. An earlier development over far western Wisconsin would place our area in the crosshairs, while a later development over eastern Wisconsin would favor a path entirely outside our area and in Lower Michigan. At any rate, the MCS will have the potential to produce significant severe winds in excess of 75 mph given the very impressive thermodyamics. Moreover, deep layer shear is expected to be enhanced this afternoon as a 50+ kt enhanced mid- level jet along the southern periphery of the MCVs shifts overhead. Accordingly the threat for damaging hail and tornadoes would exist, as well. And, not to be forgotten, torrential downpours will also accompany these storms given PWATs at or just above 2". It appears the main window of severe threat for the area will be after 2 or 3 pm this afternoon through 7 or 8 pm this evening. KJB 1 Link to comment Share on other sites More sharing options...
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!Register a new account
Already have an account? Sign in here.Sign In Now