Winter Weather Definitions

...WHAT DOES THAT WARNING MEAN?...
                

Winter is just around the corner. When a warning is issued will you know what it means...and will you know how to respond.   During this Colorado Winter Weather Preparedness Week...please become familiar with our list of potentially life-saving winter weather products.

 
This list contains the warning and advisory criteria for Colorado east of the continental divide. Criteria west of the divide will be provided today in a separate issuance by the NWS Grand Junction forecast office.
 

OUTLOOKS

A HAZARDOUS WEATHER OUTLOOK is issued daily by each National Weather Service office in Colorado. The outlook provides information on potentially hazardous weather out to 7 days into the future.  Also... THE WEATHER STORY...a graphic of expected hazardous weather is posted daily on National Weather Service web sites serving Colorado.

 

WATCHES AND WARNINGS

SNOW

A WINTER STORM WATCH is issued when hazardous winter storm conditions are possible within the next 3 to 4 days, but the timing, intensity, or occurrence may still be uncertain.

A BLIZZARD WATCH is issued when blizzard conditions are possible in the next 12 to 36 hours.

 
In contrast...winter weather WARNINGS are issued when potentially life-threatening winter weather events are likely to occur.
 
A WINTER STORM WARNING is issued for the occurrence of heavy snow or any combination of heavy snow and other events. Other events include such things as blowing snow or very cold wind chill temperatures.
 
WARNING CRITERIA for HEAVY SNOW is defined by the following amounts.
 
IN THE MOUNTAINS...8 inches of snow in 12 hours, or 12 inches or more in 24 hours. 
  
ON THE PLAINS...6 inches in 12 hours, or 8 inches or more in 24 hours.
 
 A BLIZZARD WARNING is issued for the plains when the following conditions are expected to occur for at least 3 hours:
  • Sustained winds of 35 mph or greater
  • considerable falling and/or drifting snow
  • with visibilities frequently 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.

 

WIND

A HIGH WIND WARNING is issued for the following conditions:

MOUNTAINS and FOOTHILLS

  • sustained winds of 50 mph or more for at least 1 hour...or gusts of at least 75 mph for any duration.

LOWER ELEVATIONS

  • sustained winds of 40 mph or more for at least 1 hour...or gusts of at least 58 mph for any duration.

A HIGH WIND WATCH is issued when high wind conditions are expected to develop in the next 12 to 36 hours. 

A WIND CHILL WARNING will be issued for the following wind chill temperatures...when combined with sustained winds of at least 10 mph.
 
MOUNTAINS...minus 35 degrees Fahrenheit or colder
LOWER ELEVATIONS...minus 25 degrees Fahrenheit or colder
 

A WIND CHILL WATCH is issued when wind chill warning criteria are possible in the next 12 to 36 hours.

A DUST STORM WARNING will be issued for the following conditions:

 
Visibility reduced to 1/4 mile or less in blowing dust...and sustained winds of 25 mph or greater for at least one hour.

 

ADVISORIES

 
Advisories for winter weather are issued for potentially hazardous conditions.
 

A WINTER WEATHER ADVISORY is issued when:

 

MOUNTAINS...4 to 8 inches of snow falls in 12 hours, or 6 to 12 inches in 24 hours

LOWER ELEVATIONS...3 to 6 inches of snow falls in 12 hours, or 4 to 8 inches in 24 hours

Or when the following conditions are expected:

  • 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 precipitations types, such as snow and sleet, that will impact traavel conditions.

 

 

A WIND CHILL ADVISORY is issued whenthe following is expected:

MOUNTAINS...wind chills between 25 below and 34 below zero

LOWER ELEVATIONS...wind chills between 18 below and 24 below zero

 

A DENSE FOG ADVISORY is issued for fog reducing visibilities to 1/4 mile or less.

 
Additional public information statements will be issued throughout the remainder of this week to help you know how to respond when hazardous winter weather threatens.

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