Yellowstone National Park officials released a temporary plan for snowmobiles Monday that would allow 318 commercially guided machines in the park each day during the upcoming winter.

The park is scheduled to open for the season in a little more than 40 days, and Park Service officials must still submit the proposal to the public for two 15-day comment periods before it can take effect.

Park Service officials had to scramble to come up with a plan after U.S. District Judge Emmet G. Sullivan in September threw out a 2007 proposal that would have allowed 540 snowmobiles in the park each day, saying the Winter Use Plan violated the Organic Act and ignored the advice of Park Service scientists.

In the latest proposal, Yellowstone would also allow 78 commercially guided snow coaches in the park each day. The plan would stay in effect for up to three years while the Park Service formulates a permanent plan.

In Grand Teton National Park, the temporary plan would allow 25 snowmobiles a day for ice fishing on Jackson Lake and 25 a day on Grassy Lake Road from Flagg Ranch to Ashton, Idaho. It would also keep Sylvan Pass open for winter travel.

The proposed Yellowstone limit of 318 snowmobiles — that must employ the best available technology to run quieter and cleaner — is a little more than last winter’s average of 294 snowmobiles a day, the number favored by environmental groups for the upcoming season.

Tim Stevens, Yellowstone program manager for the National Parks Conservation Association, called the temporary plan a “step in a better direction” from the 2007 document.

“It’s important to note that, for the longer term, the number of snowmobiles being proposed still exceeds the daily average and will still damage Yellowstone’s resources,” he said. “Every scientific study has demonstrated that Yellowstone can do a better job protecting park resources by providing public access to the park on snow coaches.”

Stevens said the Park Service’s proposal to allow the new plan to remain in effect for three years is ill-advised.

Jack Welch, former president of the BlueRibbon Coalition, said limiting the daily number of snowmobiles to 318 per day is bad for park visitors and park concessionaires.

“We’re encouraged that the Park Service sees a place for snowmobiling in Yellowstone. However, we are disappointed with the number,” he said. “The 318 as a daily limit means that there will be periods of time when there will be no space available for people to enter the park on a snowmobile. It throws into question the survivability of some of the concessionaires whose main focus is on the park.”

Yellowstone spokesman Al Nash said the limit is based on past analyses.

Nash acknowledged that the daily cap is likely going to affect concessionaires.

“We were looking to find a figure that we felt was going to provide for visitor access, some certainty for communities and some reasonable allocation to our winter-use operators,” he said.

The latest proposal and instructions on how to comment are available at http://parkplanning.nps.gov/document.cfm?parkId=111&projectId=23430&documentID=25017. Comments must be received or postmarked by Nov. 17. Another 15-day comment period will begin as soon as the plan is published in the Federal Register, which is expected later this week.