THE NEXT SEVERE WEATHER THREAT ON DECK

All eyes on Wednesday for our next chance of severe weather including the risk of destructive winds and potentially numerous tornadoes. The forecast has increased to a Level 3 of 5 Risk, and Enhanced Risk, with the highest probabilities sitting just south of our area. However, there remains enough uncertainty and potential that pretty much all of our area is at risk at this point in time. There is some potential this threat level increases farther, and the area at risk changes.

Long range, high resolution modeling is indicating a broken line of thundersdtorms extending from Michigan through the central Mississippi River Valley. Storm mode is one of the biggest unknowns with this event and will determine if we are looking at a wind threat more than a tornado threat. If we do see discreet supercells for a long portion of this event, that would dramatically increase the strong tornado threat.

THE RRFS

THE GFS

THE NAM

While there are a lot of similarities in the modeling above for Wednesday, there are a number of factors that are different as well that will shape the overall threat. The GFS/RRFS for example push the warm front almost all the way to Chicago which puts our area fully in the severe risk, while the NAM is slower with the warm front and limits the threat for a larger portion of our area. The NAM, however, is much more aggressive with instability and size of the open warm sector where severe weather would thrive while the RRFS warm sector is more narrow in size.

For now we are getting a general idea on the potential area for storms and the overlap of instability and wind shear is certainly impressive. The wind shear in particular for this time of year is high end. Smaller details will be worked out in the days ahead. One note - thunderstorm potential is lacking Tuesday across the severe risk area which helps eliminate some potential failure mode.

Basically throughout the depth of the atmosphere wind speed will be near the climatological peak, well into the 99th percentile. This is a strong signal for aggressive wind shear. Notice too 850mb winds are southwest while 200mb are west/northwest. This directional shear in addition to speed shear will be enough to generate strongly rotating storms. The biggest question is whether storms can remain discreet enough to warrant a stronger tornado threat.

Machine learning forecasts are very much honed in on the severe potential Wednesday and it more centered on Missouri and central Illinois, keeping the greatest severe risk to the south which is well in line with the current Storm Prediction Center outlook. Pretty much everyhing I use to forecast severe weather is pointing at a rather high end severe weather event Wednesday situated too close for comfort to our area.

More details to come...

-Meteorologist Nick Stewart