Avalanche Forecast for Sunday, April 14, 2019
This information was published 04/14/2019 at 6:57 AM.
The Bottom Line
Wet loose avalanches will remain small and shallow, but have the power to carry you over a cliff or down long couloirs. These will most likely be produced by skier-induced sluff and are more of an issue in very steep terrain or terrain that has seen little to no skier traffic. Following safe travel rules like skiing one at a time and not crossing above your partner is a great way to manage today’s avalanche problem. LOW avalanche danger exists today; those traveling to the more out-there ravines or steeper lines should be discussing sluff management techniques before dropping in. As springtime temperatures melt the snow, our snowpack is becoming undermined and developing holes. If you can hear water rushing under the snow you are skiing, the potential for the snow to collapse is present. Keeping an eye on your partner on the streambed exit from today’s objective will be a good idea.
At midnight, summit temperatures dropped below freezing after 36 hours of staying in the 30sF and twice peeking into the 40s. Cloud cover Friday and Saturday morning helped slow rates of warming and allowed the snowpack to adjust appropriately to the change. Today is beginning clear and windy. Wind from the west will decrease and eventually shift to the south. Temperatures will climb slightly, allowing the summit to reach near the freezing mark. Clouds will develop through the day and bring precipitation in the late afternoon with close to half an inch of liquid falling by daybreak on Monday. The freezing line is a bit uncertain. Rain is likely at some point at all elevations with possible mixed precip or snow falling at upper elevations this evening and tonight.
Primary Avalanche Problem – Wet Loose
Wet loose avalanches, particularly on very steep slopes or those which have not seen skier traffic, are possible to human-trigger. Wet loose avalanches can occur when free water is present in the surface snow and release at or below the trigger point. Today, these should remain small and shallow, but still have the power to carry skiers or riders downslope if unaware.
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.
This time of year, transition can happen quickly. This is being reflected in the surface of the snow. With the summit of Mount Washington above freezing from mid-morning on Friday to midnight last night, our snowpack quickly warmed and wetted to become isothermal to at least 1 meter in depth. While this spring snowpack provides opportunities for great skiing and riding, it still has the potential to change rapidly, even hour to hour. Shade and cloud cover can quickly turn spring skiing to hard, refrozen snow and create a long, sliding fall potential. Timing and sun exposure are critical to finding great skiing. Spring melting also creates large voids under the snowpack and even holes in the surface. Open holes are now visible in places such as the Lip in Tuckerman and likely the Little Headwall by the end of today. Do not let your guard down at the end of the day just because the steep skiing is over. Lower angled streambeds currently contain the greatest potential for collapsing snow bridges.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch, though this is changing by the day. Expect ice patches, opening stream crossings and the occasional bare patch.
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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 04/14/2019 at 6:57 AM.
USDA Forest Service
White Mountain National Forest