Bridger Teton Avalanche Center
WESTERN WYOMING AVALANCHE ADVISORY
Issued on Fri March 23, 2018 6:59 PM
The storm that started early yesterday morning and ended this morning brought as much as 17 inches of snow that contained 2.2 inches of water to the mountains (this amount was measured at the Rendezvous Bowl study plot in the Tetons). During this precipitation event, temperatures were warm yesterday and cooler last night when most of the snow fell. The snow/rain line reached to approximately 7000 feet overnight, however rain fell consistently to 8500 feet during the day yesterday. In the valleys, where the temperature stayed above freezing, rain fell through the period. During the day, skies were broken and periods of sunshine drove temperatures at 9000 feet to quickly rise from the low to high twenties while low elevations rose into the forties. Summit winds were from the southwest with averages between fifteen and twenty-five miles per hour.
The new snow fell on lighter snow that has been accumulating since the last significant dry period that developed crusts and faceted snow that ended March 14. Many natural slides appear to have occurred in the backcountry during the loading event last night as the crowns were partially filled in this morning and hard to see from a distance. The ski patrol at JHMR triggered widespread activity this morning above 9000 feet. These sensitive slabs ran long distances and released on mid storm layer that developed in the new snow last night. At least one slab in the backcountry was skier triggered today on the older snow interface mentioned above. This occurred during a rapidly warming sunlit period in a very steep path known as Drew’s slide to the south of JHMR. The skier deployed his airbag and was partially buried mid slope, less some equipment. It is fortunate that neither he or anyone who might have been below him was not seriously injured during this large avalanche (pictures are posted on the website). In addition to the slab hazard, warming temperatures caused the new snow to become wet and release in very steep terrain, particularly at the 8000 – 9000 feet elevation range. In some areas, these wet slides entrained significant amounts of new snow.
FORECAST FOR Saturday, March 24, 2018
The chance for snow is to return to the high elevations by morning and continue through Saturday. Temperatures are to be slightly cooler with mountain highs in the mid-twenties. Accumulations of two to five inches are predicted. At the lower elevations overnight freezing will be followed by temperatures warming into the upper thirties.
The general avalanche hazard will be Considerable above 7500 feet. Slabs to three feet could be triggered in very steep terrain. This hazard will increase as warming occurs, particularly if that warming is accelerated by periods of sunshine. Wet loose slides may also become possible. Below 7500 feet the hazard will be low in the morning and increase to moderate in the afternoon as the snow surface quickly softens and weakens.
TREND FOR Sunday, March 25, 2018 AND Monday, March 26, 2018
The avalanche hazard will decrease on Sunday and Monday during a period of much colder temperatures and light precipitation.
For further information call 307-733-2664
To report an avalanche observation call 307-739-2607
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