Northwest Wyoming’s first major wildfire of the season grew six-fold in a day, expanding from 2,000 acres Tuesday to 12,000 acres Wednesday afternoon.

The Fontenelle Fire, burning in heavy dead and fallen timber on the Bridger-Teton National Forest about 70 miles south of Jackson, expanded from Lincoln County into Sublette County. Unusually dry forest fuels in the Wyoming Range, site of the blaze, are helping propel it, along with other factors.

“It continues to be a wind-driven fire,” Bridger-Teton fire specialist Andy Norman said. “The topographic alignment is pushing it northeast with strong southwest winds.”

No communities are threatened by the fire, but there are some small cabins on Middle Piney Road that are at risk, Norman said.

Winds near the wildfire’s center in the Snider Basin were 17 mph with gusts to 35 mph Wednesday afternoon. Gusts reached as much as 53 mph on Tuesday.

The dew point, 17.7 degrees, is “extremely low,” indicating very dry conditions, Norman said.

Managers are upgrading oversight to a “type 2” team, which has more personnel and can handle higher-complexity fires, Norman said. The existing 92-person Fontenelle team would grow by approximately 35 to 40 persons, he said.

Fontenelle was reported to the Bridger-Teton at 4:35 p.m. on Sunday and has grown exponentially ever since. Forest officials haven’t determined the cause.

On Monday, officials reported it as 100 acres. On Tuesday morning, the fire was 900 acres and 10 percent contained.

Teton Interagency Fire, which is managing the blaze, is no longer providing an estimate for the containment percentage. Heavy smoke and high winds prevented aerial reconnaissance Tuesday, and the size is now being estimated using infrared aerial photography.

Bridger-Teton has closed Middle Piney Road, LaBarge Creek Road, Coal Creek Road and Indian Creek Road, and has prohibited recreational access to the entire region. The fire remains on the Bridger-Teton, Norman said.

The fire danger throughout the Teton Interagency Fire’s district, which encompasses Teton County, Grand Teton National Park and the Bridger-Teton, was elevated to “high” on June 21. That’s the third step of five fire danger readings ranging from “low” to “extreme.”

Fire managers are considering elevating the danger to “very high,” Norman and Chip Collins, Grand Teton National Park’s fire management officer, said Tuesday.

A “very high” fire danger rating typically comes with campfire restrictions, which are already being imposed around the state.

On Wednesday, Gov. Matt Mead announced a fire ban on all state-owned lands.

“This means no open fires, charcoal grills and a prohibition on incendiary devices,” Mead said in a statement. “The ban on incendiary devices includes fireworks, tracer bullets and other explosives.”

Twelve counties — Uinta, Sweetwater, Carbon, Albany, Laramie, Natrona, Converse, Platte, Goshen, Weston, Campbell and Crook — also have instated fire bans, the statement said.

Under state law, the decision to institute a fire ban is made by county commissioners.

Wyoming Game and Fish has also banned open fires on all lands it owns and administers lands in the Laramie and Lander regions.

With Fourth of July less than a week away, Norman reminded people to be extra cautious and aware of the law.

Fireworks are illegal every day of the year in Teton County, he said.

Abandonment of still-smoldering campfires has also given the Forest Service trouble this year.

Through June 25, some 23 unattended or abandoned campfires had been discovered and extinguished by Teton interagency staff this year. Within the national park and forest, six human-caused blazes have been suppressed.