Update 1PM CST…
Visibility has generally improved across northeast Illinois and northwest Indiana this Sunday afternoon, but is still restricted in a few areas and will continue to be low along the Lake Michigan shoreline until later this afternoon (grey-shaded areas and visibility on maps below).
As the center of low pressure moves off to the northeast, the associated cold air is still expected to sweep into our area from the northwest later this afternoon/early evening – lasting through Monday before southerly winds bring a warming trend beginning Tuesday.
Dense fog has developed across the Chicago area this Sunday morning with widespread visibility less than a quarter-mile and near zero in spots. If traveling this morning, be alert to the possibility of already poor visibility suddenly dropping to near zero in some location. These conditions will be further complicated by a spotty light rain/fine drizzle. Conditions will be slow to improve with the dense fog likely persisting into mid-afternoon along and just inland of the Lake Michigan shoreline. Counties under the Dense Fog Advisory are shaded in grey on the map below as well as a current visibility map.
Low pressure will move northeast across our area into Michigan today and Ontario, Canada tonight. Temperatures will slowly warm well into the 40s, and with dew-points also in the 40s the nearly 100% relative humidity will not only cause the dense fog to persist, but also will provide perfect conditions to melt the snowpack that blankets our area – much of the snow will likely be gone by this evening. The bulk of heavier rain will pass to our southeast and a band of snow far to our north (see regional Weather Radar Mosaic below). The associated cold front will pass through from the northwest later this afternoon/evening bringing a brief intrusion of drier colder air that will persist through Monday.