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No red flag warning issued during Marshall Fire: Do criteria need to change?

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DENVER (KDVR) — A red flag warning, also known as a fire weather warning, was not issued the day of the Marshall Fire because it didn’t meet the criteria for the warning. Meteorologists are starting the conversation to see if the criteria needs to change.

Greg Hanson with the National Weather Service says that the specific criteria for issuing a red flag warning are wind speeds at or over 25 mph and relative humidity at or below 15%. Both of these conditions have to last for at least three hours.

On Dec. 30, relative humidity in the area of the Marshall Fire was around 20-30%, therefore it did not meet red flag warning requirements.

The NWS officially issues weather warnings, watches, and advisories.

Despite a red flag warning not being issued on Dec. 30, a high wind warning was in place. One of the highest gusts measured that day was 108 mph recorded three miles southwest of Boulder.

“Unfortunately, as we saw on the 30th, with that strong of wind and those dry fuels we had, just because that humidity wasn’t down at 15% we can still see extreme fire growth and behavior with that,” Hanson said.

Hanson explained that red flag warnings were originally designed many years ago to warn their partners fighting wildland fires that the weather will be more extreme because of high winds and low humidity.

After the Marshall Fire, the question now comes up if the criteria for red flag warnings need to be changed or if there needs to be a different way to warn people about high fire danger.

Hanson said at this point it is just an idea and initial conversation to start thinking about how to warn people of high fire danger in the future. He also mentioned that the strong winds were from a weather phenomena called a mountain wave that is fairly common on the Front Range during the winter meaning it’s not unusual to see a strong wind event in the Marshall Fire area this time of year.

Hanson explained that in order for any change to happen there would have to be a lot of coordination with all of the NWS’s fire, emergency manager, and media partners so that the message conveyed stays consistent.

It is important to remember that just because there isn’t a red flag warning in place doesn’t mean that fire danger isn’t high.

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