This information was published 03/08/2020 at 7:12 AM.
NOT THE CURRENT FORECAST
This is an archived avalanche forecast.
The Bottom Line
Hard, firm wind slabs are the primary snow surface you’ll find today, though keep your eye out for areas of softer snow in steep, sheltered terrain that could produce a small avalanche.
Refrozen snow, and hard firm wind slabs present the possibility of a long sliding fall where arresting a fall in steep terrain may not be possible. As you choose terrain today, consider the consequences of a fall, which could be caused by a simple stumble or lost edge on an area of exposed icy crust. You can mitigate this risk by traveling carefully with crampons, ice axe, and the ability to use them. Avalanche danger is LOW.
Yesterday, NE wind 50-60 mph shifted N then NW with increased wind speeds after dark. Temperatures remained in the single digits F and skies remained mostly clear. No snow was recorded yesterday.
Today, NW wind shifting W at 65-85 mph with possible gusts to 105 before easing off to 50-70 mph mid day. Temperatures are expected to rise to the upper teens F under mostly cloudy skies. Slight chance of snow showers may bring a trace to 1” of snow.
Tomorrow, sunny skies,temperatures warming to lower 30s F with W wind 50-70 mph. Monday night into Tuesday brings the next chance for snow, although warm temperatures may limit accumulations to the highest summits.
Primary Avalanche Problem – Wind Slab
Large wind slabs formed during last week’s 133mph west wind event are thick, firm and continue to prove unreactive. It may be possible to produce a small avalanche from small, isolated pockets of wind slab formed late last week, though no avalanches have been observed or reported since that storm. New snow falling today could build new pockets of wind slab as well. Be mindful that even a small avalanche in the wrong place, such as a steep and icy snow slope, can result in big consequences today.
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.
In avalanche terrain today, you’ll generally find three different snow surfaces.
Large firm, pencil hard wind slabs.
Scoured icy areas stripped of new snow from high winds.
Small isolated pockets of slightly softer (1F) but generally unreactive, wind slabs formed from new snow at the tail end of last week.
Where you’ll find each surface is a great example of the spatially inconsistent snow pack we often see. Skiers have recently reported dangerous, scoured icy surfaces in one gully, while a nearby gully offers chalky but edgeable turns. In some locations, one gully may present all three surfaces. If you brave the stiff wind today, be prepared for a variety of snow conditions and choose your terrain carefully.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.
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. Clickhere to check it out.
Recent snowpack and avalanche observations can be foundhere and on Instagram. Your observations help improve our forecast product. Please take a moment andsubmit 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 03/08/2020 at 7:12 AM.
USDA Forest Service
White Mountain National Forest
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