Because not all snowfalls look alike, forecasters use different
terms to describe the rate and duration of falling snow. Let me
mention the most common:  A snow squall is a heavy, brief burst
of snow that can put down a quick inch or two. A snow shower is
a moderate, but again brief, period of snow, which sometimes
gives a light accumulation. Snow flurries describe a very light
and brief snow shower, with no measurable accumulation. Notice
that each of these terms has the word "brief" in its definition:
they all describe snows that don't last long.  Steadier snows
that last, say for at least a few hours - are categorized as
either light, moderate, or heavy, depending on the visibility:
It's light snow if you can see more than half a mile, moderate
snow if visibility is between one-quarter and one-half a mile,
and heavy snow if visibility is one-quarter of a mile or less.
So there IS a method behind all that snow terminology you hear!