As snow accumulates making for a slow dangerous Friday evening commute/travel across northern Illinois into northwest Indiana and the Chicago area, to the south freezing rain/sleet mixed with snow will create very hazardous travel in that area this evening. Following is a Mesoscale Discussion issued by the National Storm Prediction Center regarding the portion of Illinois just to our south (escalloped area on the headlined map) – travel in that direction is not advised.
Mesoscale Discussion 0061 NWS Storm Prediction Center Norman OK 0407 PM CST Fri Jan 17 2020 Areas affected...northeast MO into central IL and far southeast IA Concerning...Winter mixed precipitation Valid 172207Z - 180300Z SUMMARY...Freezing rain, mixed with sleet at times, is expected to continue/spread northeast through the evening. Some areas near the I-70 vicinity will likely transition to all rain over the next few hours as temperatures slowly warm above freezing. DISCUSSION...Precipitation will continue lifting northeastward through the evening. The current surface freezing line extended roughly along the I-70 corridor across MO into IL. Areas of light to moderate freezing rain will continue in this vicinity and northward across northeast MO into central IL this evening. Where snow is currently falling, a transition to freezing rain, possibly mixed with sleet at times, is expected over the next few hours as strong warm advection results in warming aloft in a layer from approximately 900-800 mb with temperatures ranging from 29-32 degrees. Surface temperatures will continue to warm from south to north across the broader MO/IL vicinity and some areas on the southern sides of the MCD area could transition to all rain within the next few hours. Further north, freezing rain rates will generally be 0.01-0.04 in/hr, though some brief periods of higher rates are possible