This information was published 03/26/2020 at 7:00 AM.
NOT THE CURRENT FORECAST
This is an archived avalanche forecast.
The Bottom Line
Higher temperatures and sunshine today will warm the wind and storm slabs that developed on Monday night. As temperatures warm and snow becomes wet, beware of wet slab and wet loose avalanches occurring without a human trigger. As temperatures warm and snow begins to melt, avalanche danger will increase to CONSIDERABLE with human triggered wet avalanches becoming likely. South facing bed surfaces of avalanches that slid yesterday do not have this risk of avalanche but harbor a long, sliding fall risk prior to warming. You’ll need crampons and ice axe, as well as avalanche rescue gear. Keen situational awareness of the terrain and rapidly changing conditions will be necessary to avoid trouble.
Ice will loosen its grip on cliff faces today. Beware of overhead hazards. Also, don’t underestimate the pushing power of wet avalanches. Dense debris flows can be hard to escape and push with great force.
TheAMC has closed all facilities at Pinkham Notch, including the restrooms. The winter pit toilets at Hermit Lake remain open though the breezeway at the caretakers cabin remains closed, along with all shelters and camping. Please respect CDC or your local health department recommendations and recreate locally while respecting guidelines for social distancing.
Yesterday, cloud cover failed to roll in until late in the day which allowed south facing aspects to warm above freezing despite the high temperature of 16F on the summit. The temperature on the summit reached 23F overnight.
Today, the temperature at 5am on the summit is 21F and will continue to rise to the freezing point and even warmer at ravine elevations. Cloud cover may provide shade and cooling this afternoon, but only if it is thick enough. If cloud cover is thin or variable, anticipate a greenhouse effect that drives the temperature up further. Winds will remain light at mid elevations through the day with 15-30mph on the summit. A minor disturbance overnight may bring trace amounts of snow.
Tomorrow, skies will clear again but it will be a bit colder and much windier throughout the day. Expect wind from the N then NW from 55-75mph to diminish some later in the day. Wind gusts near 95mph are possible in the morning.
Primary Avalanche Problem – Wet Slab
Snow from the storm on Monday night will become wet today as temperatures rise. Triggering an avalanche will become easier as snow becomes saturated. Expect the warming temperatures to create cohesion within the new snow layer that will overcome the tendency for bonding between the new snow and underlying melt-freeze crust, forming a wet slab. Paths in the Gulf of Slides fit that description, though many shady aspects may also warm and become unstable. Today, natural wet loose and even wet slab avalanche activity is possible on or beneath slopes steeper than 30 degrees.
What is a Wet Slab Avalanche?
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
Secondary Avalanche Problem – Wet Loose
Wet point release avalanches could occur in areas that escaped heating yesterday. Warming temperatures could create conditions for wet loose avalanche primarily in steep terrain. These can be a problem on slopes where lots of snow can be entrained and push you into obstacles, through trees, or over cliffs.
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.
By Wednesday, skiing conditions were generally lousy in higher elevation areas where wind and warming on Tuesday created a crust that tormented skiers. Several steep, south and east facing avalanche paths produced wet avalanches yesterday morning that were large enough to injure and possibly bury a person. Today will be even warmer, so as temperatures rise, be wary of any slope that did not avalanche yesterday. Though areas sheltered from the wind harbored softer powder, that snow may have heated yesterday and developed a similar temperature crust. Field observations confirmed that spring corn snow hasn’t ripened yet with lots of snow settlement and rounding to go before recent snow becomes isothermal.
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. 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 03/26/2020 at 7:00 AM.
USDA Forest Service
White Mountain National Forest
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