(Updated at 11:16 a.m. MDT Sept. 17, 2019)
At 6:30 p.m. on Monday the size of the Francis Fire between Salt Lake City and Ogden, Utah was estimated at 100 to 200 acres but Tuesday morning fire officials said it spread since then to 550 acres. (Later in the morning that was changed to 365 acres.)
The weather overnight was conducive to additional fire growth, with the relative humidity remaining in the 20s until it began rising after 2 a.m. eventually topping out at 82 percent at 7 a.m. when 0.03 inches of precipitation was measured at the BEUU1 weather station near Ogden. The overnight wind speed was 3 to 8 mph with gusts up to 20 mph.
In a briefing Tuesday morning fire officials said the cause of the fire was lighting that occurred a week ago.
— Kyle Harvey (@KyleHarveyOnTV) September 17, 2019
Below is a video that apparently was shot shortly after the fire began spreading near Main Street and Haight Creek Drive.
— Jennifer Lindberg (@SweetWhimsyCake) September 17, 2019
It is not common for a lightning strike to ignite light to medium fuels, such as grass or brush as seen in the video above, and for it to smolder unreported for a week near a heavily populated area before growing into a large wildfire. But it is possible that investigators found evidence at the point of origin indicating a lightning strike and lightning occurrence data confirmed a ground strike at that location.
The mandatory evacuations ordered Monday were lifted at 10 p.m. Monday.
(Originally published at 6:47 p.m. MDT September 16, 2019)
A vegetation fire that was reported around 3 p.m. MDT Monday has spread across a slope above Fruit Heights between Salt Lake City and Ogden, Utah. Structures have been threatened and the Davis County Sheriff’s Office (@DavisCountySO) has ordered evacuations in some areas. (see map below)
At 6:30 p.m. @UtahWildfire, a Twitter account associated with a government agency, reported that the Francis Fire had burned 100 to 200 acres. A strong wind has been pushing it across the slopes and caused spotting in the grass and oak brush.
In addition to the 17 fire engines working the fire, the aircraft assigned include an MD-87, a BAe-146 (Tanker 168), and four helicopters plus an air attack ship and lead plane. Below we have one video from Twitter of an air tanker drop, and more are on Fire Aviation.
— Bryson Real Estate (@brysons) September 17, 2019
There have been many fires in the greater Salt Lake City area in the last one to two months. They all have a Utah tag on Wildfire Today.