WINTER STORM UPDATE-SNOW ENDING AS FREEZING RAIN/SLEET TAKES OVER
2:45 P.M.Update: Switch to freezing rain sweeping the area, icing problems to grow before temps break above freezing later this evening
Freezing rain and ice pellets are fast becoming the favored precipitation mode Saturday afternoon. Early snow has been replaced by freezing rain in Chicago, as well as at DuPage, Aurora and Rockford, signaling the fact that powerful 60+ mph southerly winds several thousand feet above the surface are warming the air there quickly. Roads conditions are icy and challenging--especially less traveled thoroughfares, sidewalks and driveways.
Strong warming aloft is shutting down the brief interval of crystal formation in the clouds which fueled this storm's early snowflake development. The result is ice pellets (sleet)----but even more prevelantly super-cooled freezing rain---rain which falls as liquid but at a temperature below freezing, a state in which it freezes upon contact with cold outdoor surfaces---are to dominate the next 6 hours until temperatures at the surface surge above freezing later Saturday night. Computer models indicate as much as 0.75" of the storm's total 1"+ tally may fall during this interval of sub-freezing temperatures producing significant ice accumulations. Readings will break above freezing later tonight ultimately allowing this ice to melt. The prospect that temperatures will flirt with 50-degrees before crashing behind a cold front later Sunday the period in which icing is to be a major problem is to occur from now through around 9-11 pm Saturday night.
The storm's brief spell of snow has led to accumulations of 0.5" at Midway and 1" at O'Hare as of this 2:45 pm filing. Observer Phil Rider at Mundelein reported .9" followed by a change to sleet, and here at WGN snowfall totaled about 3/4" before turning to sleet and freezing rain.
Freezing rain is now coating colder outdoor surfaces. The weight of this ice and the gusty winds accompanying it increase the risk that tree limbs and even some power lines may come down in portions of the metro area.
Further updates will appear here during the course of the storm. Be safe!
Tom Skilling WGN-TV Chief Meteorologist
Steve Kahn WGN-TV Weather Center Meteorologist