While it's been mighty cold in the Rocky Mountains these past few weeks, there's been a shortage of snow, and that could greatly affect the opening of the winter season in Yellowstone National Park.

On Friday park officials, looking first at the roads and then at the skies and forecast, said they weren't prepared to definitely say the park would open to over-snow vehicles, or wheeled rigs, on Tuesday when the winter season is set to kickoff.

"We currently have very limited snowpack in the park. The National Weather Service is forecasting some snowfall from Friday evening on through Saturday," said park spokesman Al Nash. "A decision has yet to be made regarding appropriate modes of winter access to the interior of the park for the scheduled start of winter season on Tuesday, December 15. Travel over the East Entrance road over Sylvan Pass is scheduled to begin on Tuesday, December 22."

On Friday, the five-day forecast showed high odds for at least 7 inches and possibly as much as 18 inches of accumulations by Monday afternoon.

Winter trivia fans know that the last time Yellowstone opened for winter use utilizing some commercially guided wheeled vehicle access was December 2004. That season opened with commercially guided snowmobiles and snowcoaches allowed to travel from the South and East Entrances to Old Faithful while wheeled vehicles and rubber-tracked snowcoaches were allowed from the North and West Entrances to Old Faithful. At the time, the road from Norris to Canyon and Canyon to Lake remained closed due to unsafe conditions.

It wasn't until "January 1, 2005, that travel from the North and West Entrances to Norris, Canyon, Madison, and Old Faithful changed from commercially guided wheeled vehicles to commercially guided snowmobiles and snowcoaches," noted Mr. Nash. "The road from Canyon to Lake opened for the season on January 2, 2005 using commercially guided snowmobiles and snowcoaches."

If a decision is made to open the park Tuesday to "something other than full motorized oversnow access, the park can convert to full oversnow access within a 24-hour period after receiving a significant snowfall," he added.

Yellowstone winter trivia: Using data from 1949-2005, in 16 of those 57 years, low early winter snowpack meant public motorized oversnow access to the park either was or would have been delayed until after December 15.