Ironically, our big Wednesday snowstorm arrived during what is designated as Winter Weather Preparedness Week by Mayor John Hickenlooper.

With snow season getting up and running I thought it might be worthwhile to go over a few of the definitions of for some of the watches and warnings we can see during the cold weather season that are issued by the National Weather Service.

The Winter Storm Watch is put out when winter storm conditions are possible within the next 3 days. Over the mountains the determination for putting out a watch or warning is: at least 8 inches of snow in 12 hours or 12 inches of snow in 24 hours.

For lower elevations the amounts are a bit lower: 6 inches in 12 hours or 8 or more inches in 24 hours. That watch is upgraded to a Winter Storm Warning when heavy snow is falling or will fall in the next 36 hours.

A Blizzard Watch is issued when heavy snow is expected with sustained winds of 35 mph or greater and visibility drops to less than a quarter-mile for more than 3 hours. The watch can be issued 12 to 36 hours before the storm. The watch is upped to a Warning when Blizzard conditions are happening or are expected to happen within 12 hours. In the mountains the snow amounts are the same as above, but, the wind criteria is a bit higher for a blizzard warning — 50 mph winds or higher.

A Snow Advisory is issued for lower elevations when 3 to 5 inches is expected to fall in a 12 hour period. For the mountains it’s 4 to 7 inches in 12 hours.


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