This list has the Watch, Warning, and Advisory criteria for Colorado east of the Continental Divide. Safe this list for use throughout the winter. Criteria west of the Continental Divide will be provided later today by the Grand Junction Office.
Heavy snow criteria for eastern and central Colorado are representative values applied over a large geographic area:
- Mountains: Eight inches of snow in 12 hours or 12 or more inches of snow in 24 hours.
- Lower Elevations: Six inches of snow in 12 hours or eight or more inches in 24 hours.
Winter Watches and WarningsA Winter Storm Watch is issued when winter storm conditions are possible within the next three 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 three hours:
- Sustained winds of 35 mph or greater.
- Considerable falling and or drifting snow lowering visibilities to less than one-quarter mile.
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, six 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:
- Sustained winds of 50 mph for at least one hour or gusts to 75 mph for any duration in the mountains and foothills.
- Sustained winds of 40 mph for at least one hour or gusts to 58 mph for any duration at lower elevations away from the foothills.
AdvisoriesA Winter Weather Advisory is issued:
- When general snow accumulations are expected between four and eight inches in 12 hours in the mountains and foothills and between three and six 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 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 uarter of a mile and a mile.
This week is Winter Weather Preparedness Week in Colorado. Public information statements will be issued throughout the week to give safety information and help you know how to respond when winter weather threatens.
This guest blog written by Bob Glancy, Warning Coordination Meteorologist, National Weather Service, Boulder.