Weather Alert Definitions

Winter
Winter Storm Watch
This watch is issued when hazardous winter storm conditions are possible within the next three to four days, but the timing, intensity, or occurrence may still be uncertain.

Winter Storm Warning
This 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
This warning is defined by 6 inches in 12 hours, or 8 inches or more in 24 hours on the plains. In the mountains it is defined as 8 inches of snow in 12 hours, or 12 inches or more in 24 hours.

Blizzard Watch
This watch is issued when blizzard conditions are possible in the next 12 to 36 hours.

Blizzard Warning on the Plains
This warning is issued for the plains when the following conditions are expected to occur for at least three hours:
  • Sustained winds of 35 mph or greater
  • Considerable falling and/or drifting snow
  • Visibilities frequently less than 1/4 mile
Blizzard Warning for the Foothills and Mountains
This warning is issued for the above conditions, but with winds in excess of 50 mph at the higher elevations.

Winter Weather Advisory (Lower Elevations)
This advisory is issued for potentially hazardous conditions when 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 precipitation types, such as snow and sleet, that will impact travel conditions.
Wind Chill Advisory
This advisory is issued when the following is expected:
  • Mountains - wind chills between 25ºF below and 34ºF below zero
  • Lower elevations - wind chills between 18ºF below and 24ºF below zero
Summer
Severe Thunderstorm Watch
This watch means that conditions are favorable for thunderstorms to produce wind gusts to 58 mph or stronger or hail to 3/4 inch or larger in the watch area. These watches are issued for four to six hours at a time and for a number of counties. Stay informed, watch the sky, and take cover if a severe thunderstorm approaches you.

Severe Thunderstorm Warning
This warning means that a severe thunderstorm has been detected by radar, or by a trained spotter. Take cover if you are near the severe thunderstorm.

Tornado Watch
This watch means that conditions are favorable for tornadoes to develop. It is normally issued for four to six hours, and includes many counties. If you are in or near the tornado watch area, stay informed via NOAA Weather Radio, commercial radio or television. Keep your eye on the sky and be prepared to take cover at short notice, as tornadoes can occur with little or no warning.

Tornado Warning
This warning means that a tornado has been sighted, or a developing tornado is reported by trained spotters or indicated on Doppler radar. A warning is typically issued for a small area for less than an hour. If a tornado warning is issued for your area take cover immediately!

Flash Flood Watch
This watch is issued when heavy rain may develop and result in flash flooding in or near the watch area.

Flash Flood Warning
This warning means flash flooding in the warning area has developed or is imminent. Move to higher ground at once!

Urban and Small Stream Flood Advisory
This advisory means local flooding of small streams, streets, or low lying areas such as railroad underpasses is occurring or is imminent.
            
Year-Round
High Wind Watch
This watch is issued when high wind conditions are expected to develop in the next 12 to 36 hours. Sometimes issued 6 to 12 hours in advance, if uncertainty to the high wind conditions exists.

High winds conditions are defined as:
  • Sustained winds of 50 mph or greater for one hour or gusts to 75 miles per hour or greater for any duration in the mountains or foothills.
  • Sustained winds of 40 mph or greater for one hour.
  • Gusts of 58 mph or greater for any duration in areas outside of the mountains or foothills.
High Wind Warning
This warning is issued for either:
  • Sustained winds of 50 mph or greater for one hour or gusts to 75 mph or greater for any duration in the mountains or foothills.
  • Sustained winds of 40 mph or greater for one hour or gusts to 58 mph or greater for any duration in areas outside of the mountains and foothills.
Dense Fog Advisory
This advisory is issued when widespread fog will reduce visibility to less than 1/4 mile.