Public Observation #2023-1161

May 23, 2023 11:29 AM
Observation Date:
May 22, 2023
Zone or Region:
Central Cascades
Middle Sister
Did you observe any avalanches? 
Avalanche Type:
Wet Slab
D3: Could bury and destroy a car, damage a truck, destroy a wood frame house, or break a few trees
E face of Middle Sister, R3 D3.5, 250'+ crown width, 4'-6'+ crown depth, debris field about 350' wide and running down to 8100'
None reported
Last week's heat wave did a number on the snowpack at all elevations. Lots of melt, not a lot of freeze, and some corresponding large natural wet activity. Most notably, we observed a large natural wet slab (R3 D3.5) on the exposed face lookers right of the Diller Headwall. While the date/time of the slide is unknown, the debris and crown looked relatively fresh given the recent warm temps so I would expect it happened sometime during the final days before the cool down. The crown appeared to range from 4'-6'+, stepping down into some older layers, and the 300+' wide debris field ran a long way down to approximately 8100'. The depth of the debris is unknown, but this thing certainly had some sizeable energy as it ran.

We also observed many wet loose slides peppering the steep, solar aspects Middle and North Sister, which likely happened throughout the recent heat wave. Unfortunately, this means many of the lines above the Thayer and Villard glacier are gouged and full of debris in the runouts -- hopefully, things start to smooth out with these more seasonable temps!

Yesterday, on May 22nd, we were pleased to find a very solid freeze mild temps, mild wind, and a strong sun making for wonderful corn skiing on E-SW aspects up high from about 11am on. I suspect that timeline to trend earlier as temps slowly rise throughout the week. South-facing aspects are certainly looking much more melted out than this time last year, so some lines may have some bonus scree scrambling to link snow pitches. We approached from Pole Creek and found the snow to be continuous starting around 6000'

Additionally, anyone trying to ski the Diller Headwall should be aware that the bergschrund at the terminus of the line has opened up considerably during the heatwave and is now questionable, to say the least (pictures attached). We opted not to ski it due to the uncertainty of the exit.