This advisory expires at midnight.
Tuckerman Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features.
Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle and Odell have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. All other forecast areas have Low avalanche danger where natural and human triggered avalanches are unlikely except in isolated terrain features.
AVALANCHE PROBLEM: Wind Slab is the primary concern today followed by Persistent Slabs as a secondary problem. Over the past two days 4” (10cm) of new snow loaded in on moderate to very high winds creating new wind slabs in both Ravines. Wind Slabs can primarily be found in the center and some south side locations based on SW and W loading winds. These are sitting on Persistent slabs that were beginning to be our primary problem near the end of last week. In our Tuckerman field work, we were finding some weak layers that were going to early facets, but this was sporadic and not consistent. In areas where it is located, expect the persistent weak layer beneath these layers to yield unstable test results.
WEATHER: 4” of snow, clouds and wind over the past 2 days has kept visibility poor with a thin veil muting the definition in both Ravines. The forecast is expecting a clearing trend later today as a front brings in yet another round of arctic air. Temperatures will fall to -10F (-23C) today and -20F (-29C) tonight. Conditions will warm a bit, but we expect all negative numbers into the weekend. Very high winds this morning should abate down to about 40-50mph (64-80kph) later today and through the overnight. Very cold air and wind do not create conditions for an increased stability trend, so expect avalanche problems to linger.
SNOWPACK: The potential for natural avalanches has clearly subsided from areas being “possible” yesterday, to “unlikely” today. Human triggered avalanches in the new wind slab are our primary concern today. Based on some periods of very high winds you will likely find a mix of stubborn, stiff pencil (P) hard slabs in exposed locales and softer, one finger (1F) new snow in very protected terrain under some cliff bands, ice features, and buttresses. There is a little uncertainty in our forecast this morning exactly where these different problems occur based on limited visibility. Clearing is anticipated later today which will help you make navigation and terrain management decisions, but until then clouds will make this challenging. It will be very difficult to ascertain if you are in avalanche path runouts without good visuals unless you are extremely familiar with the terrain.
In Huntington, the northern side of the Ravine has limited stability issues and less to mitigate compared to snowfields near the rim of the southern side. The exits up high in the Escape Hatch and South have pockets to manage under a Low rating. In the Moderate rated Central, Pinnacle and Odell you will find issues lower down such at the base of Odell’s first ice pitch. Generally, in Tuckerman you will find more stability on the north and south sides compared to more problems in the Sluice, Lip, Center Bowl and the Chute. Although all of Tuckerman is rated Moderate these 4 areas harbor the greatest potential for a larger avalanche based on the size of the slopes, the potential for surface wind slab avalanches stepping down into deeper persistent slabs and their start zone steepness. Our persistent slab concerns are found mostly in these 4 areas and are of a limited to minor issue in other Tuckerman locations, and not much of an issue at all in Huntington.
Christopher Joosen, Snow Ranger USDA Forest Service