NWS Lincoln, IL -- SWOP event summary

February 17, 2014

An area of low pressure tracked from the Texas panhandle on Sunday, February 16th to northwest Indiana by the evening of Monday, February 17th...producing a wide variety of wintry precipitation across central and southeast Illinois. With the low tracking directly through the area, enough warm air was drawn northward to result in primarily rain south of I-70. Further north where cold air remained entrenched at the surface, mainly snow fell along and north of a Canton to Bloomington-Normal line. In between across the rest of central Illinois, a wintry mix of freezing rain, sleet, and snow occurred. An upper air balloon released by NWS Lincoln at midday on the 17th revealed a layer of unstable air above 9000ft aloft. As the low pressure system approached, it interacted with this elevated instability to produce scattered thunderstorms across the area. Where thunderstorms occurred, enhanced precipitation rates led to quick accumulations of snow and/or ice. Once the low moved into northwest Indiana, the precipitation diminished from west to east during the mid to late afternoon.

The greatest snow accumulations from this system were north of the surface low track, primarily along and north of a Canton to Bloomington-Normal line. Snowfall in this area was generally in the 3 to 5-inch range, with isolated higher amounts. Further south, the snow was much lighter along the I-72 corridor: however, sleet and freezing rain accumulations became an issue. Some areas from Jacksonville...northeastward through Decatur...to Danville received as much as one quarter to one third of an inch of ice. This led to quite a few power outages, particularly in the Decatur area. Only minor snow and ice accumulations occurred in southeast Illinois along and south of I-70, as surface temperatures quickly became warm enough to support all rain.