Expire Wednesday at midnight 12-18-2013
Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Bowl, Chute and Left Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.
Huntington Ravine has Moderate and Low avalanche danger. Central and Odell gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. In all other areas, natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.
AVALANCHE PROBLEM: The problem is predominantly Wind Slab due to storm snow loaded by the subsequent strong winds from the alpine zone and yesterday’s light afternoon accumulation. There was a lot of avalanche activity that occurred sometime on Monday. This was verified in Tuckerman’s Lip, above the main Headwall, the Chute, Left Gully, and Hillman’s Highway. In Huntington, avalanche crowns or debris were seen in Central, Odell and South. Some of the areas of hang fire and areas that didn’t avalanche I would probably start calling Persistent Slabs as they transition from being Storm Slabs. Cold temperatures and a clear Monday night have led to little settling or consolidation of these leftover slabs and it’s possible that some early faceting may be recognizable by today. Diminishing winds and a scant 1.25” (3cm) of 5% snow from yesterday shouldn’t change things too much from Tuesday’s forecast however additional snow showers are expected this afternoon likely adding to today’s general Wind Slab problem. This has bumped Left and Odell from Low to Moderate today. Based on the cold low density snow we have been having lately wherever you find relatively soft snow in steep terrain, you should be concerned about triggering an avalanche requiring cautious travel.
WEATHER: Light snow that fell yesterday afternoon into the evening came on a SW and WSW wind from 35-50mph (56-80kph) with several higher gusts. Since midnight these winds have settled in from the W and slowed significantly. Currently velocities are in the low teens mph, but will ramp up quickly into the afternoon and shift once again. Winds may hit a hurricane force (77 mph) from the NW late today before shifting back to the W and gaining strength into Thursday, perhaps gusting to 90mph (144kph). Along with the afternoon shift today we can expect more snow showers with some measurable accumulations, but they should stay light.
SNOWPACK: Winds today, perhaps reaching over 70mph (112kph), will transport the 1+” (3cm)from yesterday and any new snow we may see today. But is very unlikely to move much snow from the weekend storm that the gusts, reaching 108mph (173kph), couldn’t do on Monday. Although new wind slab that developed after dark last night, and may develop this afternoon, shouldn’t be substantial you would be smart to expect some thin new wind slabs. I bumped Odell and Left gully to Moderate based on the potential of where they may be at later today. Although still at Low, climbers should pay attention to the approach snowfield under Pinnacle in Huntington. Low density snow sluffing off the ice may have built new wind slab concerns in this pocket. Approach climbs with caution; it’s not uncommon to for people to trigger avalanches on the slope leading up to intended climbs. Other areas posted at Moderate yesterday and today may drift to the upper end of the rating definition based on the amount of snow we see this afternoon. Anticipate some of these areas facing the E and SE, such the Tuckerman Center Bowl and Lip, to be riding the fence between Moderate and Considerable.
- Safe travel in avalanche terrain requires training and experience. This advisory 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.
- Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
- For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.Posted 833a.m. 12-18-2013. A new advisory will be issued tomorrow.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856