Avalanche Advisory for Saturday, April 14, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features. 

Tuckerman Ravine has MODERATE and LOW avalanche danger. All forecast areas in Tuckerman Ravine have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. The exception to that rating is The Little Headwall which has Low avalanche danger.

The Inferno Pentathlon is happening today with the ski leg starting at the upper Sherburne/Hillman’s junction. Use extra caution when driving in the area and know that some folks will be in a hurry hiking on the Tucks trail.

AVALANCHE PROBLEM: 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. 

WEATHER: Overnight, rain and freezing rain fell on our already moist snowpack with temperatures at or just above the freezing point. Hermit Lake collected .4” (1 cm) of rain with no snow on the board in the past 24 hours. A high temperature of 6C was recorded in the same time period. Near but just above freezing temperatures are expected in our avalanche terrain this morning along with a mixed bag of new precipitation types. The new precipitation and warm temperatures will continue to stress and weaken the snowpack until freezing temperatures return later today. Be mindful of the effect that even a degree or two of cooling can have on our snowpack if skiing or riding. 

SNOWPACK: Above freezing temperatures have persisted in our terrain for the past 24 hours. Combined with the overnight rain, these conditions are warming and wetting the snowpack and will continue to until air temperature drops and precipitation returns to frozen forms later today. Prior to yesterday several layers of generally soft slab, totaling up to two feet in thickness, existed above an older melt freeze crust in our upper snowpack. A surface layer observed at only a few inches thick was reactive to skier triggers yesterday. Moisture and warmth are in the process of converting these layers into a singular and more uniform layer of wet snow. This process will increase stability with a refreeze, but as of this morning it creates our wet slab avalanche problem. Also of note yesterday was significant wet roller ball activity in lower terrain and particularly the Lower Snowfields. While we expect the smooth and steep slopes less affected by roller balls to be of greater concern for avalanches today, it’s certainly an indication of rapid warming affecting the snowpack. Roller balls, ski and boot tracks, and generally soft wet snow will all contribute to less than ideal conditions once a refreeze occurs. Expect stability to increase but for the propensity for other injuries to increase, with long sliding falls ultimately becoming a key concern.

Please Remember:
• 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.
• Posted  7:30 a.m., Saturday, April 14, 2018. A new advisory will be issued tomorrow.

Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2018-04-14