We're watching the wave of energy for Monday night and Tuesday as it tracks over the region. There is a possibility of some frozen precipitation with the northern fringes of precipitation as it approaches and moves through the region. The wave itself looks to be trending a bit faster, not substantially, but enough to where the potential for conversational coating snowfall or even sleet accumulation could occur across the northern and western burbs...perhaps even into Philadelphia. Since the trend is speeding up slightly and the front itself will have just cleared through the region, temperatures will be falling but how far we fall before this system moves in remains to be seen.
It's a tricky forecast because colder air is working in as precipitation moves through. The infamous "how cold, how fast" type of setup where precipitation works in as the atmosphere is cooling. Precipitation will work in on Monday night and should be out of the region by Tuesday morning's rush hour...it's an overnight event.
The Euro, GFS, and NAM all suggest the possibility of temperatures dropping just enough to get some conversational snow in and around the region. Models vary a bit on extent of snow but the Euro does show the potential for an inch across the far western and northwestern burbs.
The NAM shows that some of the precipitation that falls may be in the form of sleet -- colder air pushes in at the surface and will be more dense than the milder air that it is replacing. Even with precipitation falling, the mid layers of the atmosphere will be mild at the start so we could see a rain to sleet or rain to sleet to snow storm system for some folks.
Accumulations, again, will be minor, but the possibility of a coating of snow or sleet in some parts of the region is worth posting about...but since this will fall at night the timing of the event is such that it shouldn't cause significant impacts on travel around the region.