Hi John, I live in northern Illinois and this morning we were under a "winter storm watch" now it has been changed to a "snow advisory" but the snow totals have not changed. My question is, what makes the difference between a "snow advisory","winter storm warning", and a "heavy snow warning"?
P.S Thank you for the web site and all the work you do to maintain it!!!

tdq600.

Here is a link to the terms the NWS uses:
http://www.noaanews.noaa.gov/stories/s794c.htm

In a nutshell, for anything weather related (winter storm, tornado, hurricane, etc...) A watch means conditions will be favorable for the weather event to happen within the next 12-48 hours. Whereas a warning is issued when the event is imminent or is already occurring.

An advisory is similar to a warning, but is issued for conditions less severe than a warning.

-John

Just to add to John's link, here is one that is more specific on the criteria for the different warnings and advisorys, summer and winter, for the Great Lks. area. Good Stuff

NWS Seasonal Weather Terms

tdq600-

I have been wondering the same exact thing for about 20 years now. I just never thought to ask "The Man" (John) about it.
Thanks for asking it for me.

John-
Thanks for the awesome link to the explanations of each event.

L8R
Todd