Bridger-Teton Avalanche Center
Backcountry Avalanche Forecast
Greys River
This Avalanche Forecast is expired

Issued: Thursday, February 23, 2023 - 7:02AM
Expires: Friday, February 24, 2023 - 12:00AM
Author: Frank Carus

THE BOTTOM LINE

At elevations above 9,000', triggering a large avalanche remains likely on steep, wind loaded slopes. Many lower elevation areas also contain wind drifted slopes, as well as 1' to 2' thick slabs of storm snow that sit on top of weak snow. It is possible to trigger an avalanche large enough to bury a person on steep slopes even near valley bottoms. Evaluate the snowpack and terrain carefully for wind drifts, shooting cracks in the snow surface or sounds like whoompfing that indicate weak layers  in the snowpack. 

Avalanche Danger
Friday, February 24, 2023
10,500'- 9,000' 3 - Considerable
9,000'-7,500' 2 - Moderate
7,500'- 6,000' 2 - Moderate

Avalanche Problem #1
Wind Slab
All Aspects above 7500'
Likely
Small (D1) - Large (D2)

(2/22/2023)

20-30" inches of snow fell in the Greys River zone since Saturday. Since then, winds howled from the southwest, west and north even at lower elevations. You are likely to find wind stiffened snow that may still be reactive to your weight in many wind-exposed locations and aspects. So far, challenging weather conditions have limited the number observations (and potential human-triggers) but a number D1-1.5 natural avalanches have been observed at lower elevations. Due to strong winds yesterday and continuing snowfall, these slabs may remain reactive today. Keep an eye out for shooting cracks, drifts and pillows. Remember that atypical wind directions, like the north wind yesterday, create wind slabs in unusual locations.
 
Avalanche Problem #2
Persistent Slab
W-N-E all elevations, SW-SE above 7500'
Possible
Large (D2) - Very Large (D3)

A significant slab was added to locations that hold weak snow, particularly at lower elevations.  Many avalanches were observed or triggered yesterday that indicate the sensitivity of buried  weak layers. Triggering an avalanche will be most likely on weak snow recently buried within the top 1-3 feet of the snowpack. The drought condtions and cold clear nights prior to the most recent storm resulted in widespread facet growth near the surface.  While not the weakest of weak snow grains, they are not to be trusted.  Perform stability tests near your intended line and consider terrain factors that could create problems like convexities, buried rocks or slope angles over 35 degrees.  

Low-elevation slopes have very weak snow. Any slope steep enough to slide, regardless of elevation, should be assessed carefully. Conditions remain sensitive, especially in wind loaded areas where slabs are thickest. So far, upper elevation avalanches on the more deeply buried persistent layer (Jan 26th layer) have not been observed and it's possible that these locations with a much deeper snowpack over the buried weak layers will remain dormant.

Forecast Discussion

The recent storm delivered a strong dose of water weight (20-30" with 2-3" water) and along with it, another test to our snowpack. Today's forecast is supported by a fair number of direct observations that show that most avalanche activity above 9,000' was a result of wind loading and up to 4' in depth. Areas below that elevation saw widespread avalanche activity thgouh avalanches were smaller. Of course smaller is a relative term. Some of these were just large enough to bury a person and definitely large enough to carry someone into rocks, trees and terrain traps. So far, upper elevation avalanches on more deeply buried persistent layers have not been observed and it's possible that these locations with a much deeper snowpack over the buried weak layers will remain dormant. This dormancy seems unlikely in shallower areas at mid elevations and below that have received the first "test" with this snowfall. Keep the weak snow in areas with a thinner snowpack in mind as you venture out. 

Weather Forecast

A cold front moved down across the area early yesterday which replaced the warm, wet storm with cold temperature, light snow showers. The Tetons picked up 2" new snow, the Greys River zone 1-3" while Togwotee received an inch. Wind speeds was strong in the morning from the east in Togwotee, and from the north in the Tetons and Greys. Tempereratures bottomed out late last night in the negative teens to negative twenty. 

A warming trend is beginning though temps this morning remain just below zero in the Tetons, -10 to -15 in Togwotee and the Wyoming Range. Light snow showers  continue today with up tothree inches possible in the mountains. Wind will be from variable across forecast areas at 15-20 mph above 10,000'.