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 8 p.m. Thursday for the Denver metro area, Palmer Divide and Lincoln County.
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.
That means a huge portion of Colorado will see critical fire weather. The NWS warning calls for winds of 20 to 35 mph with gusts up to 50 mph and low humidity.
Southwest breezes will strengthen Thursday, giving the Front Range a breezy and rather mild day with highs warming into the pleasant 60s. Then late Thursday into Friday, windy conditions and blowing and drifting snow will be found over much of Colorado's high country, causing travel impacts.
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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