A Red Flag Warning is posted for the Sierra Front including Southern Washoe, Carson, Douglas, Storey, Lyon, and far southern Lassen Counties on Friday from 2pm-10pm because of strong winds and low relative humidity. As a general rule of thumb, the criteria for a Red Flag Warning to be issued is less than 15% relative humidity, wind gusts over 30mph for at least three hours, and dry fuels. A Red Flag Warning can also be issued because of lightning, especially if there is not a lot of rain expected. The National Weather Service also has the flexibility to issue a warning if the relative humidity or wind gusts don’t quite reach the general thresholds.
Fuels also play a big role in fire danger. Unfortunately, with our latest heat spell our fuels are much drier now, and critical enough for the National Weather Service to issue a warning. Fuels in the Tahoe area are not quite as dry, but you’ll still want to be fire aware. A wet spring could be delaying their fuels from drying out a bit. It’s also cooler up there.
We live in a region where fire danger is always a concern, but when a Red Flag Warning is issued the danger is higher. Fire Warnings are region based. What might be of a concern in Florida, is a typical day in Reno. It’s normal for winds to be strong in western Nevada during the late evening hours because of the Washoe Zephyr. It’s also normal for our relative humidity to be below 20% in the summer time. This means we should always be fire aware. A Red Flag Warning is issued when wind gusts are over 30mph for at least three hours, on Friday they could reach 30mph for up to six hours. The Washoe Zephyr typically produces wind gusts in the 20’s with an occasional wind gust in the lower 30’s.
You’ll want to avoid any activities that could cause a spark when a Red Flag Warning is posted. This includes things like mowing, grilling, having a campfire, four wheelers, dragging chains on the ground, and target shooting. Strong winds can propel a fire and make it grow much faster than normal.
