Posted 8:10 a.m., Wednesday, April 6, 2011
Tuckerman Ravine has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. There are two exceptions to this rating. 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: Central, Pinnacle, Odell and South Gullies have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecast areas in Huntington Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
Today’s ratings are similar to yesterday’s but for completely different reasons. Concerns about rain and warmth creating unstable snow conditions have faded with the invasion of a cold front. Today we are back into a mid-winter like snow event with light density snow being blown into lee areas of the ravines. Cold air kicked out the sub-tropical temperatures around mid-day yesterday and rain transitioned to snow. We now have around 3″ (7.5 cm) of new light density snow and we are expecting anywhere from a trace to 2″ (5cm) of additional accumulation today. WNW winds are exceeding 80 mph (129 kph) on the summit but are forecasted to back down to 45 to 60 mph (72 to 97 kph). These forecasted wind speeds will be ideal for transporting new snow into both ravines forming wind slabs. I suspect new wind slabs are going to be easy to trigger and there may be enough wind loading of the new snow to result in some natural avalanches as well. The most likely area for natural avalanche activity is in the Sluice, Lip and Center Bowl in Tuckerman Ravine. Given the low water content of new snow and recent winds, I think you will find a lot of variability in surface conditions today. The older snow that has recently refrozen will likely be exposed in areas that are not protected from wind. This is easily identified by its grayish color and icy surface. While this snow is now stable, don’t be lulled into thinking you will find that in more sheltered areas.
High pressure will move in tonight and it looks like we will have a few days of decent weather. Snow stability issues will be limited to what is occurring today and clear weather will give us a good opportunity to assess the extent of these issues tomorrow morning. I know that spring skiing is on many of your minds and this window looks like the first good opportunity to capitalize on spring-like conditions. Realize that icy conditions are dominating the mountain and we may have lingering avalanche concerns. Hopefully this will change but you need to be prepared for winter.
The Harvard Cabin is now closed for the season. Camping in the Cutler River Drainage is only allowed at Hermit Lake Shelters.
- 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 caretaker at Hermit Lake Shelters.
- This advisory expires at midnight. A new advisory will be issued tomorrow
Brian Johnston, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856