27/02/2024
Even though we are less than 12 hours out from the onset of severe weather, there is a LOT of uncertainty. As of right now, we are looking at an all or nothing scenario...let's talk about what we're seeing that raises the uncertainty for tonight's severe potential.
When we forecast storms, we look for convective inhibition, also called a cap or lid. When the atmosphere is capped, storm development is limited. If the cap erodes (which is possible given record warmth and increasing dewpoints today), then storms would be able to develop.
Should the cap remain in place this evening, storm development would be limited or nonexistent. It is possible we see a bimodal setup, with storms going both north and south of our area, with our forecast area seeing absolutely nothing.
Hi-res model guidance is catching on to a possible bimodal setup, however, at this point, with the severe threat being less than 12 hours away, looking at soundings, surface observations, and the mesoscale environment is sometimes better than looking at model guidance.
It is also possible that the cap erodes, storms develop, and the severe threat materializes. Looking at the 12Z sounding from NWS Lincoln IL (see below), favorable ingredients are there for severe storms; this includes steep mid-level lapse rates of 7-8C and strong 0-6 km shear.
We also have record warmth today, strong forcing/lift ahead of an advancing cold front, as well as we will be favorably positioned under the left exit region of the jet streak at 300mb. These parameters indicate a good environment for storms to develop if the cap can erode.
Timing for storms, should they develop, will be after sunset and into the overnight hours. Large hail (2"+) would be the main threat, but damaging winds and a few tornadoes will also be possible. Stay weather aware and have ways to receive warnings!
Additionally, temperatures sharply fall behind the cold front tonight. We'll have highs in the low 70s today, then much colder tomorrow. Highs Wednesday will be at midnight, with temperatures falling throughout the day. Wind chill values will be in the single digits to teens. From summer-like to winter in less than 24 hours!
