Avalanche Forecast for Friday, January 18, 2019
This information was published 01/18/2019 at 7:06 AM.
The Bottom Line
The recipe for small wind slabs is on the table today with a ripe wind direction and speed for loading. However, it’s likely we will lack the snow which serves as the crucial ingredient, at least during daylight hours, to build those slabs. If you are out climbing (recommended) or skiing (not so much) bring your crampons for the rugged, hard snow and keep an eye on the weather, especially later in the day. Overall stable conditions today, even with a small amount of new snow, should keep us at a LOW danger rating today. If we receive the upper end of the forecasted 1-3” of snow, the potential for small, human-triggered avalanches may exceed that rating, especially as evening approaches.
Low tide conditions continue with no new snow recorded in the past 24 hours around the range. Summit temperature at 6 am is 0F with wind from the southwest near 40 mph. A weak cold front will pass through this afternoon and bring snow shower activity with it. Accumulations should be light, with forecasts ranging from one inch up to three inches. Wind will shift west and ramp up into the 45-60 mph range in the afternoon. Dry air in place and limited moisture in the system seem likely to keep snow accumulations low. Temperatures will fall again tonight to near -10F with wind remaining from the northwest in the 40-55 mph range. After a fairly calm but seasonably cold day tomorrow, a significant winter storm arrives in the evening with temperatures staying quite cold through the storm. Low density snow will likely create challenging conditions for a number of reasons with “postholing” through thigh-deep snow, even with snowshoes, being among them.
Primary Avalanche Problem – Wind Slab
Wind slabs have been unreactive for several days now bringing generally safe avalanche conditions to the range. Some pockets of softer snow exist but also seem to present generally stable conditions. The possibility of finding and triggering a thin spot in a hard wind slab resting on the ice crust is unlikely but not impossible. New wind slabs could develop late in the day, especially if we receive 3” of new snow.
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.
Remnants of the 1.5” of snow that fell Wednesday and developed small but softer wind slabs are scattered around in the most sheltered locations of the terrain. Overall, the snow surface in avalanche paths is dominated by thick hard wind slabs or avalanche debris from the widespread January 10/11 avalanche cycle. Facets have been observed around the ice crust under the hard wind slabs that remain, though triggering these tough slabs remains unlikely. The incoming snowstorm will be greeted by fully developed avalanche paths, at least in the eastern half of the compass rose. This includes slopes and gullies with a more south-easterly aspect.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.
Thanks to the 72 people that came out to LL Bean in Freeport for the avalanche awareness talk last night. We’ll see you there next year. Check our events page for two more talks coming up at REI stores in Reading and Boston.
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 01/18/2019 at 7:06 AM.
USDA Forest Service
White Mountain National Forest