Fri-Sat, March 14-15th – Severe T’Storm Outbreak – Update #4

(11:30AM – Friday, March 14th, 2025) Friday morning update on a strong storm system that will move through the region, with a broken line of rain/t’storms and severe t’storms (QLCS) expected to sweep across the state from late this afternoon through early Saturday morning.

Timing…
•Late Friday Afternoon – Early Saturday Morning, March 14-15th.

Location…
•All of Illinois.

Impacts…
•A level 1 to 4 severe t’storm risk is in place state-wide for the likelihood of isolated to numerous severe t’storms.
•Damaging winds and tornadoes will be the threats from activity. Large hail will also be possible.
•Environmental conditions will be supportive of the possibility of occurrences of significant severe t’storms in the form of: Strong tornadoes, several tornadoes, long track tornadoes, damaging winds 75MPH+ and/or corridors of widespread/significant wind damage.

Update…
•With this update, little change was needed, as the going forecast is on track. Unless conditions warrant last-minute changes that would necessitate another update, this will be the final forecast issuance. Additional real-time updates will be provides as needed throughout the event.

Discussion…
•As a strong storm system moves through the region, a broken line of rain/t’storms and severe t’storms (QLCS) will develop this afternoon across portions of Iowa and Missouri. This QLCS will rapidly track across the state between late this afternoon and early Saturday morning, mixed mode in nature (Line segments and supercells). The setup with this storm system is one of a classic early spring variety, featuring ample shear/forcing and lower instability/moisture. Damaging winds and tornadoes will be the most favored threats, though large hail will be possible as well. A tromng jet streak will be overhead, with a strong low-level jet just off of the surface and ample mixing, which will allow damaging wind gusts to reach the surface even with weaker activity. This will also allow for the potential of significant severe t’storms capable of producing damaging winds of 75MPH+ and/or corridors of wind damage. QLCS/supercell tornadoes will also be likely, with weather guidance soundings showing extreme low level shear and nicely curved and elongated hodographs. There will be the potential for strong tornadoes, given the aforementioned environment, with long track tornadoes also possible given the the high movement speed of activity. The QLCS/supercell tornado threat will be maximized across portions of Central and Southern Illinois, where a late surge of moisture and instability will likely occur just ahead of pressing activity.