Avalanche Forecast for Friday, March 13, 2020
This information was published 03/13/2020 at 7:02 AM.
The Bottom Line
Rain falling on new snow that falls this morning may create conditions for small, wet snow avalanches in isolated areas or extreme terrain. Yesterday, snow surfaces in most avalanche terrain were refrozen and hard and are likely to remain so until warming occurs midday. LOW avalanche danger exists today. If you brave the icy snow surfaces, mixed precipitation or rain, depending on your elevation, watch for unstable snow on isolated terrain features.
If you’d like to hear a conversation with Lead Forecaster Frank Carus, go to the latest MWAC Outreach interview with Andrew Drummond on Soundcloud. They discuss a long sliding fall incident on Monday, strategies to deal with hard, steep snow, communication and first response strategies, the upcoming weather for the weekend and issues surrounding the pandemic.
Yesterday was cloudy and cool with snow and ice on the ground remaining cold down to around 3,000’. No new precipitation was recorded.
Today, expect sleet, freezing rain and some snow accompanied by increasing wind, mostly from the south. This morning is starting out with light snow showers that may bring 1-3” and wind from the south at 50mph. Temperatures at 5:30am were 17F on the summit, 29F at Pinkham. Precipitation will change to sleet and rain midday before changing back to snow in the evening. All total, around an inch of SWE should accumulate during the day.
Tomorrow, wind will continue to increase, ultimately hitting the century mark with gusts to 120mph from the NW. Temperatures will fall Friday night to around 7F on the summit as upslope snow showers bring up to 2” new snow. Expect increased avalanche danger and wind slabs.
Primary Avalanche Problem – Wet Slab
Wet slab avalanches may be triggered in wind sheltered areas that contain any soft snow. The danger level and size of any wet slab activity is dependent mostly on enough new snow accumulating and forming wind slabs before becoming wet. History has shown that more rain or a softer snowpack would be required for a more dangerous Lip waterfall avalanche to occur today. Wet loose activity should be limited in size and remain mostly harmless.
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.
This morning, forecasters shared stories about miserable mountain experiences in the rain. Hardy folks may find adventure today with softening snow but you’ll need rain gear and micro-spikes in your kit in addition to your beacon, probe, and shovel. Look out for spontaneous ice and rockfall from cliffs and gullies at most elevations along with deteriorating trail conditions where post-holing may occur even on previously packed trails.
The Sherburne and Gulf of Slides ski trails remain snow covered to Pinkham Notch. Snow coverage is remarkably good on most of these trails due to largely below freezing temperatures preserving this snow most of the winter.
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 03/13/2020 at 7:02 AM.
Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest