Avalanche Forecast for Saturday, March 30, 2019
This information was published 03/30/2019 at 6:57 AM.
The Bottom Line
Warming temperatures through the day will make wet loose avalanches a relevant concern for those traveling on steep snow slopes. Wet loose avalanches, or sluffs, are expected to be small today but could still easily cause a fall. Watch for softening wet snow through the day as a sign that it may become possible for you to initiate a wet loose sluff. Avalanche danger is LOW for all forecast areas. Natural and human triggered avalanches are unlikely, but watch for unstable snow on isolated terrain features.
High temperatures yesterday were above freezing for most of our terrain, with the summit of Mount Washington holding a few degrees below 32F. A half inch of snow fell at high elevations on W wind that decreased from around 60 mph to under 40 mph. Below freezing temperatures returned overnight for most of our terrain including low elevations, though around 4000’ is actually the warmest elevation band in our terrain this morning at 33F. Similar warming is forecast for today. By this evening, all elevations should be above freezing with highs in the upper 30’sF in the notches. Cloudy skies will bring light amounts of mixed precipitation, totaling less than a tenth of an inch, which could include snow, sleet, freezing rain, and rain. Wind shifts SW and should increase through the day today towards 60 mph on the summits. All elevations are forecast to remain above freezing through tonight as heavier precipitation begins early tomorrow, falling mostly as rain but shifting to a wintry mix and ultimately snow late in the day.
Primary Avalanche Problem – Wet Loose
Small, wet loose avalanches may become possible as temperatures rise though the day. These sluffs are easiest to initiate with skis or a snowboard. As you evaluate snow conditions and choose terrain today, remember that a small avalanche can easily cause a fall. A small, wet loose sluff in high consequence terrain can be a big problem. Look for increasing boot or ski penetration into wet snow as a sign that you may be able to initiate wet loose sluff today.
What is a Wet Loose Avalanche?
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Periods of warming and refreezing since Thursday have helped stabilize wind slabs which formed up to a week ago. These wind slabs sit on a robust crust to which they seem well bonded. Slight warming today makes wet loose sluffs a key hazard to manage, but we don’t expect warming to the point of making wet slabs an avalanche problem. You may still be able to find dry snow on the surface, especially at upper elevations, but you’re more likely to find moist to wet snow. If the weather forecast of rain and warmer temperatures pans out for tomorrow, expect decreased stability of our upper snowpack with wet slab avalanches becoming an avalanche problem.
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. 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 03/30/2019 at 6:57 AM.
Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest