Dangerous avalanche conditions exist, especially at the middle and upper elevations of the Tetons. Human triggered avalanches are likely due to the combination of snowfall, wind loading, and buried weak layers. Travel in avalanche terrain is not advised.
The Tetons have received 10-20 inches of snow (0.8-1.8" snow water equivalent) in the last 24 hrs with ridge top winds averaging out of the SSW in the 20-30 mph and temperatures in the teens and single digits. Slab depths could be in excess of 4 feet at the upper elevations.
Buried weak layers exist within the snowpack, especially on high elevation southerly aspects and mid elevation northerly aspects. Steep rocky starting zones on upper elevation Northerly and Easterly terrain also contain weak faceted snow. Southerly aspects have a crust/facet combination from the mid November period at the upper elevations in steep terrain. Northerly aspects have buried surface hoar and near surface facets, especially at the mid elevations in wind sheltered areas. Very steep and rocky terrain on North/East aspects is also suspect. Slab depths could be in excess of 4 feet at the upper elevations and around 2-3 feet at the mid elevations.
Well the pacific low pressure system that started off near the mouth of the Columbia has really produced, especially for the east side of the Tetons. Rendevous Bowl and Raymer have picked up a respective 1.8 and 1.5 inches of snow water equivalent in the last 24 hrs. The west side of the Tetons picked up significantly less, with Chief Joe reading 12 inches of snow and 0.84 inches of snow water equivalent in the last 24 hrs. We'll see if the west side can catch up in terms of inches of snow today in the post frontal regime.
Winds have been out of the SSW for the last 24 hours, shifting more westerly after frontal passage some time around midnight last night. Ridge top winds have been pretty consistent in the 20-30 mph range with gusts near 60 observed on top of Rendevous. With temperatures in the teens and single digits, wind slabs are likely in excess of 4 feet in upper elevation terrain on northerly and easterly aspects.
Weak snow structure exists in a somewhat patchy network throughout the range. Upper elevation southerly terrain has a problematic structure but with primarily SSW winds it is unlikely to be severely loaded with the exception of SE. Upper elevation northerly and easterly terrain in steep, rocky areas also harbors weak snow. Mid elevation northerly terrain contains buried surface hoar and near surface facets that formed during the mid November period. With 1.5 inches of moisture on the east side all of these layers are getting tested.
At the mid elevations the persistent slabs will be smaller in size due to the lack of wind loading, but these slabs could lie in drainage features where terrain traps are present.
WYDOT performed avalanche hazard mitigation on Teton Pass and triggered an avalanche that put 10 ft of debris on the highway.
