Avalanche Forecast for Thursday, April 16, 2020
This information was published 04/16/2020 at 7:03 AM.
The Bottom Line
Some new snow may build into wind slabs today and tonight. Though small, the wind slabs will complicate travel in steep terrain where refrozen surface conditions are bulletproof. The avalanche hazard is LOW today, due to these small but potentially sensitive wind slabs. Lower elevation areas may require snowshoes where limited traffic and a breakable crust lead to post-holing conditions. Crampons and micro-spikes are needed at higher elevations.
Rescuers should respond with a surgical mask or high quality homemade mask for themselves along with hand sanitizer and/or wipes. Due to wide community spread of the virus, every patient and rescuer may be a coronavirus carrier so act accordingly. In the Cutler River Drainage, we have an extremely limited supply of N95 masks which will be reserved for the patient care provider(s) and the patient. Continue to maintain your distance from other rescuers and use a mask when forced to work closely together or ride in a vehicle together. Surface contact remains an equal or greater threat than airborne spread so know what your hands are doing at all times.
As always, rescuers without PPE will be turned away or reassigned. This includes beacon, shovel and probe. Also, like a beacon, a mask is just one tool to help keep you safe during a rescue. Also like a beacon, a mask requires training and experience to use properly. N95 masks should be reserved for close quarters and inside work.
Yesterday, the high temperature reached 14F on the summit under mostly clear skies before dipping down to 7F last night. Just over an inch (3cm) of snow was recorded at Harvard Cabin during this period.
Today, expect highs to reach into the teens F again today with an inch of snow this morning and another round of showers later this afternoon which could deliver another 2”. This morning, wind will be from the west at 35-50 mph before diminishing slightly mid-day before ramping up again as the next round of snow showers arrives.
Tomorrow, skies will clear with temps in the mid-teens again. NW wind in the 40-55 mph range until shifting to the NE. Two inches of snow may fall later in the day.
Primary Avalanche Problem – Wind Slab
Look for signs of instability in these wind slabs, such as shooting cracks, before committing to a slope. The soft snow will make for easier cramponing, but change course when snow depth reaches your boot-top or you find yourself on or below a large slope or gully or over consequential terrain. New and building wind slabs will be particularly prone to triggering.
What is a Windslab Avalanche?
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch with most trails still covered with enough snow to slide a rescue litter. The exception is at lower elevations and south facing aspects.
The Lion Head Winter Route remains the easiest route to the summit from Pinkham Notch but requires an ice axe, crampons (not just micro-spikes) and possibly a rope. This is a mountaineering route and requires solid skills for a safe, timely ascent.
Safe travel in avalanche terrain requires training and experience. This forecast is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
Avalanche danger may change when actual weather differs from the higher summits forecast.
For more information contact the US Forest Service Snow Rangers, AMC visitor services staff at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or seasonally at the Harvard Cabin (generally December 1 through March 31). The Mount Washington Ski Patrol is also available on spring weekends.
Posted 04/16/2020 at 7:03 AM.
USDA Forest Service
White Mountain National Forest