This Advisory expires at midnight, Wednesday 3-07-2012
Tuckerman Ravine has Considerable and Moderate avalanche danger. The Lobsterclaw, Right Gully, Sluice, Lip, Center Bowl, Chute, and Left Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Hillman’s Highway and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.
Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and the Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
Today is a full on avalanche brain teaser with a number of factors for the avalanche enthusiast to consider. Three dominant issues and their exact timing are the important parameters that have generated today’s avalanche forecast. Since the weekend, the upper mountain picked up about 7” of very low density snow with low to moderate wind speeds ever since. Yesterday’s peak wind of 65 from the NW did a fairly respectable job pushing around most of this alpine snow, but today winds are expected to ramp up, possibly hitting the century mark this afternoon. This will augment the current snow plumes already at the ridge potentially causing some new loading concerns. While this occurs, continued warm air will be escorted by the high winds causing the first substantial warmup for the cold snowpack in a while. Although we did see a little bit of solar gain yesterday, today’s warm up will be more significant. There is a strong likelihood for avalanche terrain to remain above freezing overnight before increasing in temperature even more on Thursday with a chance of rain. The summit is expecting the mercury to be in the mid thirties F today, while here at Hermit Lake it is currently just shy of 40 degrees already. There will be a battle between increasing temperatures and wind speeds today. As winds continue to pick up they will help keep many snow slopes cool even as the ambient air gets warmer. So the exact timing of each of these and how they affect one another is the key factor to observe today. A number of strong lee areas from W winds, with a SE and S aspect component, will warm the most today in the direct sunlight. I have an nagging concern about these areas and the potential natural slope failure as the tensile strength of cold slabs get baked out over some under riding facets and unconsolidated snow weaknesses below.
So we have both some new cold slab issues due to loading snow with increasing winds and then some intense warming mostly on protected southern aspects. Ultimately I believe there is a good chance new snow loading, high winds, and increasing wind issues will balance each other out coming to a reasonable equilibrium. However, I cannot ignore that these factors may escalate enough to possibly cause a natural avalanche hence the “Considerable” avalanche danger rating for a number of our largest snowfields and particularly those facing S. In Huntington these S faces are posted at “Low” due to their overall thin ribbon like nature and how high W winds rip these narrow gullies more readily than in Tuckerman. This should keep the majority of S faces cool enough to limit the concern.
Tomorrow, slopes may still be above freezing at dawn with the chance of rain. This may continue to escalate the avalanche danger so be prepared for continued natural avalanche problems with a higher magnitude than today.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856