What Does that Watch, Warning, or Advisory Mean?

The National Weather Service will inform you about developing hazardous weather through the use of outlooks, watches, warnings, and advisories. 
 
This list has the watch, warning, and advisory criteria for Colorado along and east of the Continental Divide. Heavy snow criteria for eastern and central Colorado are representative values applied over a large geographic area...
 
Mountains - 8 inches of snow in 12 hours
                      12 or more inches in 24 hours
  
Lower elevations - 6 inches of snow in 12 hours
                                  8 or more inches in 24 hours
 
Winter watches and warnings
 
A winter storm watch is issued when winter storm conditions are possible within the next 3 days, but the timing, intensity, or occurrence may still be uncertain.  
 
A winter storm warning is issued when heavy snow is occurring or will develop in the next 36 hours. The heavy snow may be accompanied by wind greater than 15 mph and blowing snow. 
 
A blizzard watch is issued when blizzard conditions are possible in the next 12 to 36 hours. 
 
A blizzard warning is issued in lower elevations when the following conditions are expected for at least 3 hours...
    
·         sustained winds of 35 mph or greater.
·         considerable falling and or drifting snow lowering          
·         visibilities less than 1/4 mile.
 
A blizzard warning is issued in the mountains and foothills for the conditions above, but with winds in excess of 50 mph at the higher elevations. 
 
A wind chill watch is issued when wind chill warning criteria are possible in the next 12 to 36 hours.  
 
A wind chill warning is issued for wind chills of at least minus 25 degrees on the plains, and minus 35 degrees in the mountains and foothills.
 
A freeze watch is issued when freeze conditions are possible in the next 12 to 36 hours. 
 
A freeze warning is issued during the growing season when widespread temperatures are expected to drop to below 32 degrees. 
 
A high wind watch is issued when high wind conditions are expected to develop in the next 12 to 36 hours. Sometimes it will be issued late in the first forecast period...6 to 12 hours...if the potential for high wind exists...but there is some uncertainty. 
 

A high wind warning is issued for the following conditions...

  • Mountains, Foothills and nearby adjacent plains including Fort Collins, Boulder, and western Denver suburbs - sustained winds of 50 mph for at least 1 hour or gusts to 75 mph for any duration in the mountains and foothills
  • Lower Elevations away from the foothills - sustained winds of 40 mph for at least 1 hour...or gusts to 58 mph for any duration at lower elevations away from the foothills.    
                                                               
Advisories
 
A winter weather advisory is issued...
  • When general snow accumulations are expected between 4 and 8 inches in 12 hours in the mountains and foothills, and between 3 and 6 inches in 12 hours at lower elevations. 
  • When falling snow is accompanied by blowing snow to cause travel problems due to lower visibilities.                                

  • When wind-blown snow will occasionally reduce visibilities and create a hazard for travelers. 

  • For freezing drizzle or a mix of precipitation types, such as snow and sleet, that will impact travel conditions.
 
A dense fog advisory is issued when fog will reduce visibilities to 1/4 mile or less.
 
A wind chill advisory is issued on the plains when wind and temperature combine to produce wind chill values of minus 18 degrees to minus 25 degrees. 
 
A wind chill advisory is issued for the mountains and foothills when wind and temperature combine to produce wind chill values of minus 25 degrees. 
 
A frost advisory is issued during the growing season when temperatures are expected to drop to between 32 and 35 degrees on clear calm nights.

A blowing dust advisory is issued when blowing dust reduces visibilities to between a quarter of a mile and a mile. 

 


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