BOULDER, Colo. — The National Weather Service (NWS) has issued a Red Flag Warning for the Denver metro area and plains of southeast Colorado.
The Red Flag Warning will be in effect from 11 a.m. to 7 p.m. Tuesday for the Denver metro area, Interstate 25 corridor and stretching across the entire Eastern Plains of Colorado.
Tuesday calls for southwesterly wind gusts up to 45 mph and humidity values as low as 9-percent along with above-average temperatures. Daytime highs will reach the mid to upper 70s in Denver.
That means a huge portion of Colorado will see critical fire weather. Dry and windy conditions are forecast and residents are asked to avoid activities that could cause a spark that leads to a fire, like outdoor burning.
Warm and windy today
Cooler and wetter weather is on the way mid-week to alleviate fire danger concerns. The next system moves in Wednesday afternoon as clouds increase followed by scattered rain showers and isolated thunderstorms. Afternoon highs in the Denver area will only warm into the upper 50s.
Overnight Wednesday into early Thursday, rain will transition into snow showers, with a continued rain/snow mix throughout the day Thursday. Afternoon temperatures will drop as well, into the upper 40s and lower 50s.
Friday, mostly cloudy skies stick around along with scattered rain and snow showers. Highs drop a bit further, into the mid 40s.
Red Flag Warning
While fire danger is high anytime it is dry and windy, meteorologists look for specific conditions to issue Red Flag Warnings.
Here’s the criteria:
- Relative humidity at or below 15%
- Wind gusts of 25 miles per hour or greater
- More than 15% coverage of dry lightning in an area
A thunderstorm is considered dry if it produces less than a 10th of an inch of rainfall. These conditions must last for three or more hours in a 12-hour period.
The humidity and wind duration criteria can be a little above the threshold if there is a specific weather event forecast that could spike high winds, or shift the winds suddenly, like the passage of a strong cold front.
The vegetation must also be considered critically dry. The weather forecaster works closely with land managers to determine if the grasses, shrubs and trees are at critical levels.
Red Flag Warning areas are communicated by using political boundaries like county lines, but it should be noted that weather cannot be contained by those boundaries. Fire weather conditions may exist outside of the shaded warning areas.
Reporting from 9NEWS Meteorologist Cory Reppenhagen contributed to this report.
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