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.
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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.
The amount of snow available for transport by increasing westerly winds is driving the avalanche problem today. Deeper areas of new snow may be attractive for skiing and riding but bear in mind that the new snow may not be well bonded yet to the old refrozen surface. As wind increase today, be on the lookout for wind slabs growing over a foot thick and may fail on softer new snow beneath. Lower angled terrain may have the best skiing since the icy bed surface will be lurking just below the new snow. The potential for wind slab avalanches in many areas is a reminder that it is not springtime in the mountains yet.
Wet slab avalanches will be possible to human trigger this morning, with colder temperatures gradually refreezing the snowpack and reducing instability late today into tonight. Multiple layers near the surface may be capable of producing varying sized avalanches. First, sluffing action of ice pellets yesterday proved to create unstable and reactive, though isolated, slabs low in avalanche paths. These and similarly new slabs formed from the mix of sleet (ice pellets), snow, freezing rain, and rain may present pockets of instability in much of the terrain, though wetting from rain overnight has likely reduced sensitivity to a human trigger. Second, deeper slabs which have become increasingly wet could produce large avalanches, also possible to human trigger and unlikely to avalanche naturally, though we’re not ruling out this possibility entirely. Finally, snow falling today and tonight on increasing W wind may build to form new wind slabs by the time this advisory expires at midnight tonight.
Rain, which could be heavy today, will make wet slabs today’s primary avalanche problem. Today’s precipitation type will be the primary driver of instability in the snowpack. If we receive more plain rain, wetting and warming will decrease stability through the day. A greater proportion of frozen mixed precipitation will have a lesser impact on the stability of our currently refrozen and stable snowpack. Today’s Moderate rating is distinctly different than Moderate ratings issued a week ago. Last week, new snow and wind made small avalanches possible in a number of areas. Avalanches were much more likely and much smaller than the large avalanches which are possible but less likely today. It’s a low probability and high consequence kind of day. If the weather doesn’t keep you out of the mountains, be mindful that though natural avalanches are unlikely today, they could be large and run a great distance.
We are currently in the freeze portion of a prolonged melt-freeze cycle that began on Friday which is largely eliminating avalanche concerns for the day. With continued below freezing conditions today, long sliding falls will be much more of a hazard today. Crampons, an ice axe, and the ability to use them will make travel in avalanche terrain possible. Climbers should be aware of the potential for ice dams as the current freeze may trap flowing water. This trapped water will be looking for a pressure release valve in the form of an ice tool or screw placement. The thaw over the past two days has also reopened holes in the snow on the Little Headwall, making this no longer an advisable route to exit Tuckerman Ravine. Many skiers and riders were seen removing skis and boards and trying to down climb the combination of refrozen snow, ice, and verglassed rock. Hiking down the Tuckerman Ravine Trail to Hermit Lake will be both faster and safer at this point.
Wet avalanches due to melting and liquid precipitation will be possible today. These avalanches are likely to be limited to loose-wet or point release type but a larger, wet slab avalanche is not out of the question in areas that previously had thicker layers of dry wind slab. The Lip, Center Bowl, and Central Gully fit this profile and deserve extra caution. A small wet slab or loose-wet avalanche can also serve as a trigger for a larger avalanche or entrain more snow than expected. Mind your runouts today if you venture into steep terrain and protect yourself and your belayer when climbing into larger snowfields. Avalanche concerns will diminish with the return of freezing temperatures later today and be replaced by slide for life conditions once surfaces have refrozen.
Wet slabs will become the primary avalanche problem today as prolonged above freezing temperatures continue to warm the recently dry upper snowpack. The sun may make an appearance today. If we see sunshine for an extended period, human triggered wet slab avalanches may push toward likely on southerly aspects. Without lengthy sun affect, the soft slabs that blanket much of our terrain should behave similarly on all terrain in the ravines. Loose-wet sluffs and point releases should be on your radar, and like wet slabs, will be possible to human trigger on many aspects. It’s worth noting that wet slab avalanches are notoriously difficult to forecast, with natural avalanches tricky to predict and the tipping point between unreactive and touchy to a human trigger often being a very fine line.
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This website is provided through a partnership between the White Mountain National Forest and the White Mountain Avalanche Education Foundation. The avalanche forecast applies only to backcountry areas, not operating ski areas, and describes general avalanche conditions which vary locally. The avalanche information provided is the sole responsibility of the USDA Forest Service.