NWS Lincoln, IL -- SWOP event summary

May 10-12, 2014

Central Illinois once again avoided widespread severe weather during this most recent period of stormy conditions. Even though most locations missed the bad weather, a few spots reported very large hailstones, damaging wind gusts, and locally heavy rainfall.

Saturday Night into Sunday Morning (May 10-11)

A warm front lifting northward toward central Illinois served as the focusing mechanism for showers and thunderstorms Saturday night into early Sunday morning. An upper-level disturbance tracking eastward through the Plains interacted with the front to produce a cluster of storms across Missouri during the evening that tracked east-southeast along the boundary into south-central Illinois. The strongest storms remained further southwest across Missouri: however, storms with locally heavy rainfall spread as far north as a Winchester to Pana line. A SWOP observer in Murrayville (Morgan County) measured 1.70, while another SWOP 1 mile southwest of Woodson (Morgan County) picked up 1.90.

Sunday afternoon and evening (May 11)

As the warm front lifted northward, a very warm and humid airmass arrived across central Illinois on Sunday. With temperatures climbing well into the 80s and dewpoints reaching the upper 60s to around 70, the atmosphere became very unstable by afternoon. Luckily there was no clear boundary to focus storms along: however, widely scattered thunderstorms popped up in the highly unstable environment. One cell tracked northward through portions of Richland and Lawrence counties, producing penny-sized hail 3 miles west of Birds (Lawrence County) and golf ball-sized hail near Sumner (Lawrence County). Another storm dropped quarter-sized hail in Shelbyville and destroyed a metal building and knocked trees down just east of Shelbyville. Other storms produced tennis ball-sized hail near Greenup (Cumberland County) and baseball-sized hail in Towanda (McLean County)!

Monday evening (May 12)

An approaching cold front triggered a broken line of strong thunderstorms from central Iowa southward into northern Arkansas Monday afternoon. The storms tracked eastward across the Mississippi River into west-central Illinois during the evening. Despite a very unstable airmass, weak low-level wind-shear and the presence of an anticyclonic circulation aloft prevented the storms from becoming severe. 40-50 mph wind gusts were common along the leading edge of the storms as they tracked eastward through the Illinois River Valley and across the I-55 corridor. Some minor wind damage occurred in Tazewell County, including some tree limbs being blown down in East Peoria and a few trees and power lines being knocked down in Pekin.