CIPS seems to be thinking the best analog is April 15th, 2011. That event spoofed a lot of forecasters, so I can see why the SPC would be bullish on this event to be on the safe side in the event we get another scenario like that.
Based of the discussion from the SPC, first high risk will be tomorrow. Number of tornadoes will be above average around 1401
edited to not copy cheese; didn't even see his post