Avalanche Forecast for Thursday, March 19, 2020
This information was published 03/19/2020 at 7:12 AM.
The Bottom Line
A stout ice crust exists on terrain where recent snow has been scoured away. This ice crust is impenetrable to booting or microspikes in most places and creates a slide-for-life situation, even on lower angle slopes. Wind slabs linger on north facing aspects today and should be assessed carefully. A small avalanche could be a big problem given the icy bed surface. Avalanche danger will rise to MODERATE today with new snow and rain showers creating the potential for human triggered avalanches.
Yesterday, clear skies and low wind speeds allowed south facing slopes to warm despite high temperatures in the teens on the summit.
Today, low pressure to our south will bring some snow showers to the summits with rain showers at lower elevations. Wind will be from the south from 20-35 mph with a trace to 2” snow possible. At 5:30 am it is 33F at Pinkham Notch, and 16F on the summit where it is expected to reach into the upper 20’s F later.
Tomorrow, expect a washout with up to a half inch of rain all the way to the summit. Temperatures will drop significantly after the rain event and bring slide-for-life conditions back for the weekend.
Primary Avalanche Problem – Wind Slab
Wind slabs on shady aspects remained cold and dry yesterday but were on the reactive side of stubborn in sheltered areas. Slabs in more exposed terrain were denser and unreactive with the sun and last nights refreeze helping to settle them. New snow or rain may stress slabs on certain aspects and terrain features. Though not enough rain is expected to create a wet snow avalanche problem, the rain could impact the weak interface beneath existing slabs. The faceting occurring beneath the ice crust is a wild card unlikely to affect avalanche size or potential in most common paths but is worth considering in obscure wind sheltered areas with infrequent avalanche activity.
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.
A stranded individual yesterday created a learning opportunity about the value of the proper equipment and research for any hike or climb in the range. The ice crust in wind exposed areas is bullet hard and without crampons, an ice axe, and solid experience or training to use them properly, you could be risking a long sliding fall that could lead to injury or death.
Spring avalanche center operations
During this challenging time, we know that backcountry skiing, climbing and hiking will offer needed opportunities for recreation and escape. We will continue to forecast avalanches and other mountain hazards through it all, but with some changes to our operations that are designed to protect snow rangers, ski patrollers and the public. The changes are based on current recommendations from public health professionals.
- Social distancing – we’ll gladly offer information in person in the courtyard at Hermit Lake, or anywhere else you find us, but help us keep our distance. We’ll try to be positioned so we aren’t surrounded by a crowd to maintain our 6’ spacing. CDC recommends no groups larger than 10 people, fewer is even better.
- Rescue – the team will follow best practices for EMS providers. In our case, this includes having a smaller staff of ski patrollers and possibly snow rangers, available to assist you. As always, be prepared with the knowledge and equipment to perform your own first aid and rescue and count on being enlisted to assist in a litter carry.
- Risk – consider the added consequences of a trip to the hospital as you make your decisions in the backcountry. Now is a good time to dial it back.
This is the time of year when large crowds begin to arrive in Tuckerman Ravine. Many experienced skiers choose to AVOID Tuckerman Ravine on busy days (read Saturday and Sunday) due to the hazards created by the increased number of inexperienced or unlucky skiers and riders falling or dropping things onto them. This season, there are plenty of hazards to manage including rapidly changing snow and weather conditions, long sliding falls, icefall, avalanches, crevasses, moats and undermined snow.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.
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.
Details on daily snowfall totals, precipitation type, total depth of snow and other information can be found on our page devoted to snow study plot data. Click here to check it out.
Recent snowpack and avalanche observations can be found here and on Instagram. Your observations help improve our forecast product. Please take a moment and submit a photo or two and a brief description of snow and avalanche information that you gather in the field.
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 03/19/2020 at 7:12 AM.
Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest