I’m often asked online why one particular storm is a “Winter Storm Warning,” and one is an “Advisory” etc etc. Those terms are explained in the chart above from the National Weather Service Indianapolis office. (An excerpt is shown above – here’s the full size version.)
Blizzard warnings are issued when the NWS expects sustained winds or frequent gusts to 35 mph or more for at least 3 hours and considerable falling and/or blowing snow that reduces visibility frequently to less than a quarter mile.
Different regions have different definitions. Obviously a snowier location would have a higher threshold and the folks in Memphis wouldn’t wait for six inches to issue a Warning.