Expires at 12:00 Midnight, Thursday, December 19, 2013
Tuckerman Ravine has Considerable, Moderate and Low avalanche danger. The Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Sluice, Left Gully, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecasted areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.
Huntington Ravine has Considerable, Moderate and Low avalanche danger. Central and Odell gullies have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Pinnacle and South gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. In all other forecasted areas, natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.
AVALANCHE PROBLEM: Wind Slab is the main avalanche problem today. West winds yesterday blew consistently at an ideal loading speed. The summit recorded around 3.5” (9cm) of new snow in the last 3 days which provided all the snow necessary to build potentially dangerous slabs in lee areas and gullies with an easterly and southeasterly aspect. Winds ramped up yesterday and moved the snow into these easterly start zones. Areas such as the Lip, Center Bowl and Chute may possibly slide naturally today as forecasted winds and more light snowfall continue the loading process. Persistent slabs created during and immediately after last weekend’s 14” snowfall that survived the avalanche cycle on Monday have had little chance to stabilize due to cold weather so they may contribute to the windslab instability problems.
WEATHER: The mountain has received snow 25 out of the past 28 days. Since the big winds on Monday afternoon we have picked up 3.5” (9cm) of new snow. Moderate winds on Tuesday and Wednesday morning allowed for some snow movement until about noon yesterday. Winds ramped up gusting to about 70mph (112kph) in the midafternoon flipping a switch on the mountain engulfing it in blowing snow and clouds. Loading winds from the west today will continue to be high gusting over 80mph (128kph) through the afternoon before subsiding overnight. Up to another 2” (5cm) of snow is possible through the day and another 1-3” (2.5-7.5cm) tonight before a potentially ugly freezing precipitation event comes in for the weekend.
SNOWPACK: High winds from yesterday afternoon and overnight peaking at 87mph this morning moved available snow from alpine zones that fell since Monday. New wind slabs over the past 18 hours have developed predominately on E and SE aspects due to W and WNW winds. The bullseye locations of concern in Tuckerman are the terrain features with the strongest lee of these winds, namely the Lip through the Chute posted at Considerable today. Expect to find a mix of slab hardness across these areas depending how sheltered they were from winds. It is quite likely that new wind slabs will become softer and weaker the higher you are. The main slabs that concern us are from the Lip down under the Headwall ice. The adjacent gullies, the Sluice and Left gully, follow behind as the next locales to use caution. We would consider them on the upper end of the Moderate definition hedging towards Considerable depending on snowfall totals today. In Huntington the ratings are a bit less consistent. Central and Odell are the dominate issues due to their aspect and developed bed surfaces. Staggered between is South and Pinnacle which have lower stability issues but should see building issues today, although staying within the Moderate rating. All of the aforementioned gullies and snowfields will see increasing instability today and tonight. We will get into the sleet and freezing rain event for the late Friday and the weekend tomorrow.
- 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 or the Harvard Cabin.Posted 8:20a.m. 12-19-2013. A new advisory will be issued tomorrow.
Frank Carus/Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856