Advisory – Past Fifteen Days
This is the final bulletin issued by the Mount Washington Avalanche Center for the 2017-18 season. It will remain in effect until complete melt out. Travel in the backcountry requires careful snow evaluation and mountain sense. Hazards due to snow and ice will persist until both are all gone. Summer snowstorms on Mount Washington are uncommon, but not unheard of. If venturing into the mountains, be sure to use all available resources to help plan your trip and make safe travel decisions.
Due to open glide cracks and undermined snow, the Tuckerman Ravine Trail is now closed in the Ravine between Lunch Rocks and its junction with the Alpine Garden Trail. This closure includes the Lip area, which presents numerous hazards to the recreating public and potential rescuers alike.
We are no longer issuing daily avalanche advisories for Tuckerman Ravine this season. We will continue to provide snowpack and weather information as conditions change. We are no longer monitoring conditions in Huntington Ravine, but similar hazards will persist there until snow and ice is gone. Temperatures at night will dip below freezing with daytimes […]
Cool weather will give way to an approaching warm front, though temperatures should remain somewhat cold through the weekend. The summit is forecast to remain below freezing today. Intermittent and partial cloud cover is forecast to continue through tomorrow. Saturday will also bring a chance of rain showers as temperatures warm by a few degrees. Wind today will gust to 90 mph but diminish by afternoon. Warming temperatures on Sunday may allow loose wet sluffing to again become a concern, but until then, the potential for icy refrozen snow makes long sliding falls a primary hazard. Cloud cover and a chance of showers makes Saturday not ideal for skiing. Sunday looks like a sunny day with soft snow. Glide cracks continue to grow and will soon result in closure of the Lip area.
High pressure will build into the region from Canada on Monday, keeping clear conditions until late in the week. Temperatures during the days will reach into the 40sF and nighttime lows will drop into the 30sF. Low pressure will move into the area late in the week bringing unsettled weather. Our springtime isothermal snowpack has generally reduced avalanche concerns to sluff management in steep terrain.
Rain and possibly thunderstorms on Friday will set up a clearing pattern for Saturday. Temperatures close to the freezing mark to start Saturday combined with wind speeds over 100mph on the summit may make a late start the right choice as winds may drop to a more reasonable speed later in the afternoon. Rain on Sunday will be followed by what looks like a good corn cycle next week with sunny skies, warm days and colder nights. An isothermal snowpack has reduced the concerns for large avalanches, though history has shown that intense periods of heavy rain can make the waterfall hole in the Lip do strange things no matter what the snowpack is. Sluff management should be a priority for skiers, in particular the first several of the day on each slope.
This past weekend was a perfect reminder of how fickle spring weather can be. Saturday’s crowds were delighted by sunshine and abundant spring snow while those who ventured up to the Ravines on Sunday found rain and sleet at mid elevations and 11.1” of new snow on the summit. With light and variable winds, this snow likely blanketed higher terrain. Lingering instability in the atmosphere Monday will keep temperatures around the freezing mark for another 1-3” of snow and sleet on the summit. Building high pressure on Tuesday will create a clearing trend into Wednesday along with increasing wind speeds and temperatures. New snow from Sunday will experience rapid warming over the forecast period. Those venturing into avalanche terrain should be aware of the potential for wet avalanches. While wet-loose sluffs may be slow moving, this sort of “push avalanche” can easily take a skier over a cliff or into a glide crack. New snow will also cover developing holes in the snowpack, making safe navigation that much more difficult.
Over two inches of rain and temperatures into the 40’s and 50’s over the past two days in the Ravines has consolidated the snow but has done little damage to the ski gullies in Tuckerman Ravine. A few lines such as the skier’s right fork of Hillman’s have shrunk into the barely skiable category but the Lip and most of the other main lines are still full with snow. Glide cracks are just beginning to emerge. Huntington’s ice climbs were damaged but still passable, though continued warm weather will make these increasingly sketchy due to undermining of the remaining ice and loose rocky topouts. The weather forecast is continuing to favor those with flexible work schedules and punish the 9-5ers. Rain will return Friday night and in the words of today’s MWObs forecaster “plague” the area through the weekend with rain shower activity. Warm temperatures remain in place through early Sunday which means flowing water and weak snow bridges will remain a problem especially in main watercourses. Periods of freezing temperatures may return briefly late Saturday night and more certainly Sunday afternoon and elevate the potential for slide-for-life conditions. Though icy, the Winter Lion Head Route remains the preferred option for summit hikers due to the fall hazard at the traverse near treeline on the summer trail. The lower section of the Sherburne Ski Trail is closed around the switchbacks of the Tuckerman Ravine trail, about ½ mile or 400+ vertical feet from the parking lot. In order to reduce erosion on the ski trail, please walk over to the Tucks trail and hike the rest of the way to Pinkham Notch.
Avalanches, falling rocks and ice, undermined snow, large glide cracks and icy refrozen surfaces will remain a threat in and below steep terrain as long as snow remains in the mountains. Spring weather brings about rapid changes to the snowpack and changes objective hazards accordingly. Remember to ski, climb or hike the snowpack and weather conditions that exist and not a date on the calendar!
Wet Slab is becoming our primary avalanche problem and will increase in likelihood with continued warming through the day. Wet slab avalanches are characterized by uncertainty, with the timing of peak instability for slab avalanches quite difficult to pin down. Our warming wind slabs that are becoming wet slabs also lend uncertainty to potential size of avalanches today, with large avalanches remaining a possibility. As surface slabs warm they may ultimately lose cohesion and be more likely to produce loose wet avalanches, or sluffs. Both of these avalanche problems will be most prevalent on sun exposed slopes. Areas receiving Low avalanche danger ratings today are rated so for limited potential size of avalanches.
In addition to avalanche concerns, spring hazards are emerging in the ravines. Icefall will be a key hazard resulting from today’s warm temperatures and solar heating. Areas under southerly facing ice, like Lunch Rocks, are particularly unwise places hang out. Melt water flowing under ice and potentially building up pressure will make ice dams a concern for climbers. Undermined snow will result from flowing melt water, with open holes and weak snow bridges over streams a potential concern in a number of locations including the Little Headwall.
Wind slabs that formed over the weekend will still be our primary concern today. Warming yesterday may have allowed some additional bonding of these wind slabs to the icy bed surface. While they appear similar, these slabs are variable depths across the terrain. They proved firm and stubborn to human trigger yesterday however that doesn’t mean they are stable. We would expect an avalanche today to be medium to large in size, particularly in Moderate rated terrain. Again today’s problem makes it a relatively low probability, high consequence day. With the rising temperatures today spring hazards should being part of your travel decision making. The forecast temperature and solar gain for today will help move us toward a traditional spring snowpack. However, we have not reached this point yet so please continue to bring your avalanche gear and a mid-winter mindset.
Wind slabs that formed since Friday are our primary avalanche problem. Of most concern today will be sun exposed areas holding largest slabs, like Sluice and Lip, where warming will push likelihood for human triggered avalanches toward likely and keep natural avalanches possible. Right Gully and Lobster Claw in Tuckerman and Yale Gully in Huntington should see similar affects though less capable of producing a truly large avalanche. We expect the somewhat firm wind slabs present in most of the terrain to be stubborn to a human trigger but capable of producing medium to large sized avalanches. This sets up a relatively low probability, high consequence day in which it’s plausible for the 5th or 10th skier, snowboarder, or climber rather than the 1st on a particular slope to trigger a large avalanche. Likelihood of triggering an avalanche will be slightly lower today than yesterday, but potential size of avalanches has not decreased, continuing to make the floor of Tuckerman Ravine an inappropriate place to linger.
Recent new snow and steady NW wind is elevating the avalanche danger ratings today. Wind slab is likely to be easily triggered and is not bonded well to the soft new snow or the underlying ice crust. With over 16” of recorded snow on the summit since noon on Thursday, avalanches today could be large. Recent avalanche debris in Hillman’s and Dodge’s has been observed so far through the fog and blowing snow. These recent avalanches plus continued wind loading of slopes are obvious red flags for folks considering playing in or below steep terrain today. Well-developed avalanche paths exist, meaning an avalanche today could also run far onto flat ground. Entering the floor of Tuckerman Ravine today is not recommended as this will require crossing numerous avalanche paths that have the potential to avalanche naturally. With most of avalanche terrain offering a high-risk, high-consequence scenario, lower-angled terrain like the Sherburne will be the safe choice today.
Six inches of new snow overnight arriving on increasing NW wind makes wind slab our avalanche concern today. No visibility this morning adds a degree of uncertainty to today’s forecast. We expect the snow to struggle to adhere to the ice crust which will act as today’s bed surface. This highlights a key characteristic about today’s avalanche problem; wind slab will likely be touchy to human triggers. In Moderate rated areas, the combination of wind and the slick bed surface may allow scouring to take place leaving areas of bed surface exposed. Considerable rated slopes, those in the lee of our fetch, should hold much larger areas of wind slab with limited to no old surface exposed. The potential for large avalanches exist in these areas with the possibility of natural avalanches due to continued loading through the day. The floor of Tuckerman Ravine today will be avalanche terrain as we have seen avalanches run far this year on well-developed slide paths. The hard bed surface will demand the use of crampons and an ice axe for those choosing to travel in avalanche terrain.
Due to the rugged ice crust on the mountain, you’ll find two distinct threats to safe travelling in steep terrain. The recent sleet storm finished with freezing rain which created a thick ice crust over top of a widespread glaze of sleet, wet snow and ice. New snow fell at the end of the storm on Tuesday afternoon and was able to stick in some areas, but not very well. Due to scouring of the snow, wind exposed, scoured areas above tree-line will require crampons for safe travel while many lee areas have collected enough snow to build some wind slabs. Low visibility, and other duties kept us from gathering many observations yesterday and this morning, but it seems that the ice crust will be the dominant surface in steep terrain. In areas where the new snow adhered to the ice, hand shears low in Hillman’s Highway showed that the new wind slabs failed easily in the new snow. Only a small amount (2-3”) of the recent snow was light enough to be carried by the wind and blown into our terrain but the icy bed surface will up the ante if you get swept off your feet. Human triggered avalanches are unlikely today unless you seek out these areas of wind slab. Additionally, light winds may allow the 1-2” of new snow that falls to build into small but more sensitive, new wind slabs. If we receive the upper end of the forecast amount, human triggered avalanches will become more likely and increasingly widespread.