The systems aren't really that similar I'll admit in terms of exact layout. 4/11/65 was a strong surface low that spun off a line of discrete supercells, a powerful late winter/early spring system. But I mention it because I feel first of all it could be similar in terms of numbers, and secondly because its occuring over the exact same regions that were affected on Palm Sunday. Tomorrow will likely be much more dynamic when it comes to the upper level jet. The wind profiles are incredible from this thing! Winds are backed and unidirectional at first glance, so the thinking is tomorrow will mostly be a wind event. But, the wind fields will begin to change through the day, LCLs will be low, and storms should begin as surface based rotating sups in North Central Illinois. Storms should begin to fire along a line here and progress eastward throughout the day. SB CAPE values are already approaching 3000 j/kg, and will likely be higher. Moisture return looks good. Helicity is a bit eh at this point, but very steep lapse rates will give the storms a hell of alot to build off from, and I think due to the intense upper/lower level shearing, 50-60kts, the storms will be able to rotate easily.
The biggest question for tomorrow is surface heating/clearing, which is looking more and more.... intense. Temps are expected to reach upper 80's, to potentially 90 tomorrow. 00Z NAM is very bullish, progressive, and strong, breaking out massive convection around 12z and continuing with multiple lines of supercells/squalls. WRF is also quite bullish. With the system out in the midwest decaying, and a smaller window now for an overnight/early morning MCS, that will leave us in the clear for daytime heating. Temps will soar, and soar quickly through the tri state region. Winds look to be offshore in the afternoon, so seabreeze/marine affect should be limited.
So, today's bust is tomorrow's hell. Parameters are definitely in place for major severe outbreak tomorrow, with strong/violent tornadic supercells initally, lining out and forming into a large squall line/derecho with embedded sups. The SPC has a 45% hatched area on the Day 2, they dropped the 60% in order to get the hatching on for tomorrow as 45%. If they had gone 60% hatched, that would have been a high risk. However, I feel confident that tomorrow the SPC will issue a high risk by 1630z. If I had to put out probs, I'd say 60% hatched for wind, 45% for hail, and 30% hatched for tornadoes, perhaps even 45% hatched later on. Major and dangerous day, akin to the Palm Sunday Outbreak. Would not at all be surprised to see 50 or even 75 tornado reports, some long track and violent are possible. Take this threat seriously, VERY SERIOUSLY! It could prove to be fatal if you do not and are in the highest risk areas.
