As expected rain moved through the state on Thursday starting in the late hours of the morning ahead of a warm front associated with the low pressure system in the west. Warm air advection from the south brought in warmer moist air which, according to the SPC, provided "modest destabliization", creating the possibility of convective storms to form (NOAA SPC, 2014). Along with this a strong upper-level vorticity maximum associated with a trough deepened this system creating more lift. Examining model output skew-t's for central Illinois around 18Z Thursday showed moderate values of CAPE. The system continued to strengthen throughout the day and actually spawned a few tornadoes in Illinois in the evening (see SPC storm reports). Otherwise, there were many reports of strong winds as a line of storms, associated with a cold front, progressed east. After the cold front moved through strong cold air advection moved in along with strong winds.
NOAA SPC: Day 2 Outlook 02/19/2014
SPC Storm Reports