Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
January 2, 2023
Submitted:
January 3, 2023
Observer:
NWAC Forecaster - Andy Harrington
Zone or Region:
West South
Location:
MRNP - White River Entrance

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced

Media/Attachments

Fresh debris on a W aspect. Likely started from a tree bomb or other shedding event.
Fresh drifts behind objects, plus some reverse loading. We noticed loading on both sides of the ridge and some double cornice lines.
I didn't know this track. Hopefully can figure it out as time allows.
A deeper Wind Slab pocket in steep, rocky terrain.
Numerous very shallow Wind Slabs were observed near ridgelines. In the background you can see a more sun exposed slope produced Wet Loose activity over the prior weekend.
Wind rippled slopes indicated cross-loading in open exposed areas. In steeper confined chutes, we noticed debris piles near the bottom.

Advanced Information

Weather Summary

New/Recent Snowfall:
No new snow

High clouds most of the day and gustier than anticipated east winds in exposed areas near ridgelines.

Found about half a dozen previous small shallow Wind Slabs and one larger D2, likely from over the weekend. Sun-exposed southerly slopes had signs of recent Wet Loose activity. A few larger couloirs across the valley had debris piles in them that looked a day or two old. Hard to tell if they were loose or slab, but the terrain lends to thinking that either a Wind Slab or Cornice failed and then entrained some additional snow.
Noticed one fresh debris pile that you couldn't really even call a D1. Was likely a tree bomb that grabbed some additional snow.

Snowpack Observations

We took the sleds up 410 and through the White River entrance into the park. The road is in good condition for running a sled, with adequate coverage, few whoops, and all fallen trees passable. We then toured up to around 6500' collecting surface observations. The snowpack is mostly well-settled and generally right-side up over the Christmas Crust. The depth of the crust varies due to elevation and aspect. As one might expect, there is deeper and softer snow above the crust as you ascend. On more sun-exposed slopes, a newly formed sun crust exists on the surface, even on the sides of gullies or slopes with a slight southerly tilt. In protected areas, the snow is well-settled powder, capped by weakening surface hoar.

Throughout our travels, signs of the recent windy weather were easy to spot. Textured surfaces, actively blowing snow, freshly built cornices, drifts behind natural objects, and wind-stiffened snow that felt hollow were all observed. There were wind board and shallow slabs on both sides of ridgelines with cross-loading further down in open exposed areas. On some ridgelines, we observed double cornice lines due to the switch in wind direction, but they were generally small. I was able to kick some of the newly formed cornices due to E winds on a small test slope and had them fail easily.

Found a lot of cool animal tracks. No Moose as far as I could tell.

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