The National Weather Service has issued a Winter Storm Warning starting noon today and continuing through 5 AM on Wednesday. Skiers and riders could trigger recently developed wind slabs in steep, avalanche-prone terrain. The hazard will increase this afternoon after new snow begins to accumulate. Monitor the rate of loading above 7,500 feet, and avoid rapidly loaded slopes in the afternoon. On northerly aspects above 9,000 feet, a slight chance remains to trigger full depth avalanches.
The chance remains for backcountry travelers to trigger very large deep slab avalanches on northerly aspects above 9,000 feet. If triggered, these dangerous hard slabs could involve the full depth of the snowpack. It may require larger triggers such as snow machines or groups of people to cause this failure.
In steep avalanche-prone terrain above 7,500 feet, skiers and riders could trigger recently formed wind slabs with depths of six to twelve inches. After snowfall commences, the likelihood of triggering these slides will rise as their depth and volume increase.
( Discussion is generated from the previous day's afternoon forecast. )Southerly flow aloft will abruptly change to northwesterly flow overnight. During the day on Monday, the flow will become more zonal and bring another Pacific low pressure system to the area. By Monday afternoon, snowfall rates will substantially increase. Overnight lows in the mountains will be in the mid teens before rinsing into the upper 20s during the day. By sunrise, the valleys will be in the low 20s before climbing back into the upper 30s in the afternoon. Southwesterly to westerly ridgetop winds will range from 20 to 30 miles per hour.At the lower elevations, below freezing temperatures will temporarily halt the threat of shallow wet slides before the chance returns in the afternoon. Newly and recently developed wind slabs will be the primary avalanche problem at the higher elevations.In the Tetons, the general avalanche hazard is expected to remain Considerable on Monday and will increase after the upcoming Pacific trough starts to bring new snow to the area. There, skiers and riders will be likely to trigger slabs avalanches one to two feet in depth in steep, wind-loaded terrain. The chance for natural activity will return after this next storm system begins loading the snowpack.In the Togwotee Pass and Southwest Trails areas, where significantly less snow has fallen in the past 36 hours, the general avalanche hazard is expected to be Moderate on Monday. Similar wind slabs could be triggered, but slab depths will range from 6 to 18 inches.
