This advisory expires at midnight, Thursday 3-01-2012
Tuckerman and Huntington Ravines have HIGH avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Very dangerous avalanche conditions exist and travel in avalanche terrain is not recommended. This includes the full runout paths for all slide paths. The only exception to this is the Little Headwall which has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
A WINTER STORM WARNING is in effect until 9pm tonight. Anticipated snowfall totals have slowly been ratcheting up over the past two days with current expectations of 5” (12.5cm) in the far north being likely and areas in the southern part of the State getting upwards of 15” (37.5cm). Here in the White Mountains we will fall somewhere in between with 8-12” (20-30cm), with the higher elevations leaning towards the upper end of this forecast. With 3 (8cm) of low density inches on the ground already we will continue to see snow all day and into the evening. This long duration event should deliver precipitation at a steady rate, producing another 5+/- inches (12.5cm) today and an additional 3-5” (7.5-12.5cm) tonight. This will be brought to our terrain on SE winds peaking around 40mph before decreasing later today. This will predominately load slopes and gullies with a northern facing component such as the start zones of Hillman’s Highway, Left gully, the Escape Hatch, South Gully, and Odell. Cross loading of the Chute, Center Bowl, Pinnacle, and Central is also likely.
Reaching the “High” danger rating should take most of the day with the majority of areas in the “Considerable “ range until this afternoon. The aforementioned north to east faces will reach “High” first with south facing slopes like Right gully struggling to meet the “High” rating by dark. A substantial factor in today’s stability assessment is the fairly light densities this morning at around 6%. This will load into a soft slab that will have intact crystals due to the light winds and cold temperatures. These slabs should be sensitive to triggers and be fairly weak, overall. Even the slopes that are pointing into the wind should see sluffing in steep terrain and natural soft slab releases late in the day. Expect sluffing to entrain loose snow and trigger very soft slabs on numerous aspects. The later we get into the day the more I would avoid the concept of “just going into the Ravines to take a look.” Expect the run out of a number of avalanche paths to criss-cross your intended route. For example, once you pass the “Connection First Aid Cache” on the way into Tuckerman you will be in the run out of Left gully.
Winds are expected to wrap tonight through the W to the NW and then return to the SW tomorrow. Velocities should stay light in the 30mph range on the summits continuing the formation of delicate soft slabs near the horizon of most start zones. Wind speeds will pick up substantially over the weekend from our prevailing W and NW causing a new round of avalanche problems. On a very upbeat note I would expect the Sherburne Ski trail to be pretty delightful over the next 2 days. This is a great way to kick off March, isn’t?
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856