• Steam rises off of the colorful Mammoth Hot Springs Terraces. Photo courtesy Jacob W. Frank


    National Park ID,MT,WY

Sylvan Pass Slides Delay East Entrance Reopening

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Date: May 12, 2011

National Park Service
U.S. Department of the Interior

Yellowstone National Park
P.O. Box 168
Yellowstone National Park, WY 82190
May 12, 2011 11-036    
Al Nash or Dan Hottle (307) 344-2015


Sylvan Pass Slides Delay East Entrance Reopening
Warmer Temps + Melting Snow = Park-wide Challenges
Yellowstone National Park road crews and avalanche experts are working to clear Sylvan Pass of more than 20 feet of snow and assess the continuing danger of wet snow slides that have kept the road closed since May 11. 

Four significant slides in the pass – one resulting in a debris field 70 yards wide and 20-30 feet deep across the road – have occurred in the past 36 hours. Consecutive days of mild spring temperatures continue to deteriorate high-elevation snowpack conditions and are expected to delay the reopening of Sylvan Pass for an indeterminate time until the safety of motorists can be assured.  

The park is currently redirecting heavy road clearing equipment to support reopening operations, and avalanche crews searched the slide area today with probes and canine rescue teams to ensure no motorists were caught in the slide. An unoccupied government vehicle sustained damage when it was partially buried in a major slide as a ranger was conducting an assessment of the area on foot May 11. The ranger was uninjured in the incident. Explosives were used today by park officials to try and bring down some of the heavy, wet snow. Thirteen of 18 of the detonations were successful in releasing large amounts of snow.  

This snow slide activity is expected to continue until the weather pattern returns to freezing night time temperatures. The current forecast for the Sylvan Pass area is for daytime temperatures in the 50s over the next two to three days, which will continue to warm the heavy snowpack and make it increasingly unstable. Overnight lows in the past 48 hours have dipped just enough below freezing to create a thin layer of ice, but that crust melts quickly by midday.

A blanket of heavy melting snow in the park’s interior has also contributed to the roof collapse of the RV repair facility at Fishing Bridge and caused roof damage to the Grant Village Visitor Education Center. No injuries were reported in either incident, and repair work is underway.

Yellowstone’s North and West Entrances opened April 15, the East Entrance opened prior to the slide closure on May 6, and the South Entrance opens tomorrow at 8:00 a.m. Some areas of the park such as Mammoth Hot Springs have already been experiencing the arrival of green grass and warm spring sun. Other areas remain wrapped in deep snow and chillier temperatures. Snow and ice still present in road turnouts and on thermal area boardwalks will make walking difficult or impossible for several more weeks.

May in Yellowstone means it is not uncommon for visitors to have both winter coats and shorts packed in the
same travel bag.

- www.nps.gov/yell-

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