Period of Freezing Rain Possible Thursday and Thursday Evening

The storm system for Thursday and Friday remains off the Pacific Northwest coast and we've see a lot of variation within our computer models these past couple of days in where exactly this low pressure will track.  But the potential for a period of freezing rain Thursday is beginning to grow.


The general trend within our weather forecast models has been to pull an area of low pressure a bit further to the south late Thursday and Friday.  This type of scenario won't allow as much warm air to be pulled northward as originally thought earlier in the week.  Accumulating snow is likely over central and northern Wisconsin, while a mixture of sleet, drizzle, freezing drizzle/rain and snow will be possible closer to the Stateline.


A warm front will pull close to central and northern Illinois during the day on Thursday.  Above the surface a process called 'warm air advection' will be taking place.  This is where warm air is pulled into an area, but that warm air might not make it all the way down to the surface.  This will leave surface temperatures very close to, if not slightly above, the magic 32 degree mark.  Above the surface temperatures may warm slightly above freezing, allowing any frozen precipitation that falls from the sky to melt a little before refreezing.  If this occurs, we may see some sleet during the day Thursday.  If, however, temperatures remain very close to freezing from the middle part of the atmosphere to the surface, light freezing drizzle or rain could occur.  Both scenarios seem possible through Thursday night.  The key in just how much will fall is just how much moisture can be pulled northward. 

Different profiles of the atmosphere indicate there may be some dry air in place, especially near the surface.  This could limit how much of the wintry weather occurs.  But if our atmosphere is able to saturate enough, then the wintry weather could cause some issues for the commute on Thursday afternoon and evening. 


Nothing is set in stone yet with regards to the forecast, and that's the downside of trying to forecast winter systems.  Be sure to pay close attention to the forecast in these next couple of days as we continue to go over new weather data that comes in.