Western Wyoming avalanche advisories begin
November 2, 2017
The Bridger-Teton National Forest Avalanche Center monitors snow conditions in western Wyoming and issues warnings for avalanche hazards that might impact backcountry recreationists including snowmobilers and skiers. They issued their first avalanche advisory for the 2017-2018 winter season on Wednesday, November 1st. The public can sign up to receive avalanche alerts by email. More information can be found at http://www.jhavalanche.org. Below is the first advisory.
WESTERN WYOMING AVALANCHE ADVISORY
Issued on Wed November 01, 2017 6:35 PM
SITUATION
Strong winds are preceding a significant influx of Pacific moisture.
Winds have increased over the area as a cold front moves into northern Wyoming from Montana. Since midnight average hourly wind speeds have ranged from 25 to 70 with gusts from 55 to 93 miles per hour. Skies were cloudy today and snow has begun to accumulate along the Continental Divide. Today’s temperatures remained in the 20s at an elevation of 10,000 feet.
New snow will begin to accumulate on bare ground and old snow surfaces. Those old snow surfaces are comprised of thick crust, surface hoar on thinner crusts and in some areas surface hoar on faceted snow. In steep terrain these old snow surfaces are likely to become excellent sliding layers after they have been loaded with new snow. The old snow surfaces exist on steep terrain that faces northwest, north and northeast at the upper elevations and on northerly aspects down to an elevation of 8,000 feet. Steep terrain that faces west through south to east is mostly bare of snow below an elevation of 10,000 feet.
FORECAST FOR Thursday, November 02, 2017
By Thursday night a low pressure system will move into western Washington. This system will tap into a strong push of Pacific moisture. Areas of light to moderate snowfall are forecast to develop over our mountains overnight and continue through the day. Snowfall is expected to become more widespread and increase on Friday and into Friday evening. Significant snowfall is expected in Yellowstone and the Teton, Gros Ventre and Wind River Ranges.
Several inches of new snow are likely at the higher elevations overnight. Favored areas could receive 5 to 10 inches. Another 4 to 8 inches are possible on Thursday. Temperatures will remain in the 20s in the mountains. Winds overnight will be from the west-southwest at speeds of 28 to 33 with gusts to near 50 miles per hour. Thursday's winds will continue to be from the southwest at speeds of 22 to 27 with gusts to 36 miles.
At the higher elevations strong winds and new snow will begin to load slick old snow surfaces. As the new snow depths increase, small natural and human triggered wind slab avalanches will likely occur on those old snow surfaces. Those avalanches will gain depth and size as this storm progresses. On Thursday new wind slabs could build to depths of 6 to 18 inches in favored areas. Monitor conditions and adjust travel plans accordingly. Avalanches are unlikely in areas where the new snow is accumulating on bare ground. The general avalanche hazard in steep terrain at the upper elevations is expected to be on the increase.
The general avalanche hazard may rise from LOW to MODERATE at the upper elevations if the snowfall forecast verifies.
Daily evening and morning avalanche hazard bulletins will be issued by the Bridger-Teton National Forest Avalanche Center beginning now. Updates and improvements to the internet programming necessary to post these bulletins have been conducted over the summer and therefor some new glitches are possible during the first several days of this season. Your patience is greatly appreciated.
TREND FOR Friday, November 03, 2017 AND Saturday, November 04, 2017
Periods of moderate to heavy snowfall are likely through the weekend and into Monday. New snow and wind will continue to increase the general avalanche in terrain where this new snow is accumulating on hard and faceted old snow surfaces.
For further information call 307-733-2664. To report an avalanche observation call 307-739-2607 or email avalanche@jacksonhole.com.
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