The National Weather Service has issued a fire weather watch for the Washington region for Wednesday. Some people may find that surprising in an urban region, but, even here, a combination of dry air and strong winds can promote conditions that allow for the fast spread of any fires that ignite. They are more common in open and undeveloped areas — especially outside the Beltway and toward the mountains.
The fire danger will be elevated starting Tuesday afternoon when winds could begin gusting to near 30 mph. Winds are forecast to peak Wednesday afternoon into the evening, when gusts could reach 45 mph. At the same time, relative humidity values may dip to about 20 percent in some locations. Winds will start to ease on Thursday but could still be a bit gusty.
These winds out of a westerly direction will intensify while passing over the Appalachians and then rushing down the eastern slopes — or “downsloping.” As the air descends from higher elevations, it warms, dries out and accelerates. Many firestorms, such as the disaster in Maui in August, have been fanned by downsloping winds, but winds from this event won’t be nearly as strong.
“These strong winds could result in isolated downed trees and power lines,” the Weather Service wrote in a discussion. Fires sometimes ignite because of downed lines.
The strong winds are a result of a difference in pressure between a storm in eastern Canada and a zone of high pressure sinking southward in the central United States.
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March and April are two of the more common months for elevated fire risks in the Mid-Atlantic. The fall can also present these risks, too, especially after dry summers.
Share this articleShareFire weather watches are not that unusual in our region and happen most years. Last year, they were issued in mid-April.
Fire weather watches can be upgraded to what’s known as a “red flag warning” should forecasters become confident in the elevated fire threat. The last red flag warning issued for the Washington region was on April 18 last year.
Fire threats are common in March because it is the windiest month of the year, followed closely by April. As a transition season, the spring sees the frequent passage of fronts, which are accompanied by changes in air temperature and pressure — these stir up the wind.
A lack of leaves in March both reduces evapotranspiration, a process in which plants release moisture into the atmosphere, and leads to the exposure of dry fuels.
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A mitigating factor for fires right now is that the ground isn’t unusually dry. Until the past four to six weeks, it had been a wet winter and even among the wettest on record in December and part of January. But not a lot of precipitation has fallen since, and the Mid-Atlantic, the Appalachians and the South dealt with drought during lengthy periods in 2023.
As long as it remains windy and unless significant precipitation returns, we could see additional fire threats into April.
The Weather Service says fire risks can be reduced if people avoid throwing cigarettes or matches out of moving vehicles and extinguish all outdoor fires properly, in addition to following other safety tips.
Jason Samenow contributed to this report.
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