First, I realize this is going to be a slightly tardy and generally brief Weekend Update. We’ve had a busy day on the mountain today. There were human-triggered avalanche incidents in each ravine today. More information will be forthcoming later in the weekend about these incidents. Right now my main goal is to talk about what visitors can expect on Mt. Washington this weekend. Obviously, there are some stability problems lingering, so let’s start with a recap of the past week.
On Wednesday, the latest Nor’easter rolled through, dropping 15” across higher terrain and just shy of 12” at Hermit Lake. Winds blew first from the ESE during the storm, then went dormant for a day before re-emerging last night from the NW at 30-40mph. Both the ESE and NW were responsible for loading snow into many of our forecast areas. The biggest concerns stem from last night’s winds, which were able to load up S-facing and E-facing slopes. These include many of the forecast areas of both ravines.
Today the forecast was calling for some light snow, which we did receive but it amounted to very little. Additional loading was kept at bay as the winds dropped down below forecasted speeds to around 15-20mph. I was on Lion Head ridge today, above Right Gully and Lobster Claw, and only saw the slightest amount of airborne snow. However, I did take notice that there is an awful lot of snow sitting in the Alpine Garden, waiting for either an increase in wind speeds or shift in direction. When that happens, there will be a significant loading event into lee areas.
Weather this weekend will be much like what we had today…in the clouds with chances for snow showers both Saturday and Sunday. Winds will be rather light for Mt. Washington. This will hold true until Monday or so, when we should start to see wind speeds rise.
So if you’re looking for a hike up Lion Head or other route that sits outside of avalanche terrain, the biggest environmental hazard you’ll face is low visibility. This is not to be discounted, though. Blowing snow and clouds can be very disorienting. Bone up on your map and compass skills tonight before heading up into the clouds.
If you’re looking to get into avalanche terrain, remember there are existing instabilities on the mountain in many areas. Recent avalanche activity is a solid indicator of unstable snow, and we had two incidents this afternoon. To make matters worse, additional new snow won’t need very strong winds to be loaded into wind slab on lee aspects, and with lighter winds these tend to form in the middle and tops of the gullies.
Personally, I would let the steep snow sit for a couple more days before testing it out. Here are a couple photos I took from the slide in Lobster Claw. The slide took place in the skier’s left fork, and the other one equally loaded, so don’t think for a minute that walking up to the debris pile to take a look at it is completely without risk.
This is just below the fork in Lobster Claw. The flow pulled out additional slab on the climbers left side of the gully. This crown is 34cm deep, has 10cm of new slab on top, 2cm of frozen sun crust, a thick layer of soft slab, and slid out on an older sun crust from Monday.
Here Frank is climbing above the fork, in terrain that is often mistakenly thought to be “safe” terrain. We found debris had pushed up onto the upper gully ridge farther than expected. The debris ran almost to where the hiking trail passes below the gully, in one location it was at least 8-10′ deep piled up against a tree.
So you think the bushes in the tops of gullies act as anchors? Think again. In these cases, they act as weak point and fractures tend to propagate from one weak point to another. This slide linked up the entire start zone of the right fork of Lobster Claw, and stepped down a few times after initially releasing.