| Posted: 8:11 a.m., Friday, January 17, 2003 |
Tuckerman Ravine has LOW, MODERATE and CONSIDERABLE avalanche danger today. The Little Headwall has LOW avalanche danger. Natural avalanches are very unlikely and human triggered avalanches are unlikely except in isolated pockets. Normal caution is advised. The Lower Snowfields, Hillman's Highway and Left Gully have MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are POSSIBLE. Unstable slabs are possible in steep terrain. Use caution in steeper terrain. All other areas in Tuckerman Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are probable. Unstable slabs are probable on steep terrain. Be increasingly cautious in steeper terrain.
Huntington Ravine has LOW avalanche danger. Natural avalanches are very unlikely and human triggered avalanches are unlikely except in isolated pockets. Normal caution is advised.
If you are heading into avalanche terrain today, be aware that a variety of snow conditions still exist. We have been saying this on and off for a while now, but it reflects the reality of field conditions. In Huntington Ravine there is a lot of old surface showing with intermittent patches of wind slab. In some areas this wind slab may be very hard and in others it may be soft. Try to stay on the old surface whenever possible. Isolated pockets do exist, so use your avalanche skills to find a good route and travel wisely. In Tuckerman we have found hard slab on the Northern side of the Ravine that fell within the Considerable rating. The concern isn't as much with natural avalanches as much as the human triggered probabilities. The current hard slab has enough elastic properties that we feel a skier would probably trigger a significant avalanche. The consistant cold weather has generated a large temperature gradient producing some early stage faceting. We had easy to moderate 'quality 1' shears in most locations with an occasional irregular rougher 'quality 2' shear in some pockets. With cold weather forecasted through the weekend expect facet growth to continue with the likelihood of an elevated avalanche danger rating. Cold temperatures slow down the stabilizing process so keep your avalanche eyes open even if new snow doesn't fall. Realize that avalanche skills are required to travel safely through any avalanche terrain. Areas of most concern are on the northern side of the Ravine, such as the Lip, Sluice, and Right Gully. IT WILL BE VERY COLD THROUGH THE WEEKEND. THE COLDEST OF WHICH WILL PROBABLY BE FRIDAY NIGHT INTO SATURDAY. NEGATIVE TEMPERATURES WILL PREVAIL SO EXPECT ARCTIC WEATHER. BE PREPARED.
We have been discussing various topics about avalanche activity and forecasting over the past weeks. Approximately 95% of our avalanche activity is direct action. This means that natural avalanches usually occur during, or immediately after, a weather event such as a snow or rain storm, winds that move snow into the ravines, significant solar gain on a newly deposited snow surface, etc. As forecasters in this environment, we study the weather patterns very closely to predict the likelihood of natural avalanches. Wind speed and direction, snow fall amounts and densities, rain fall amounts and intensity, and temperature changes are all very important factors in assessing direct action avalanche activity. In such a dynamic climate as Mt. Washington, weather changes extremely fast. It is important to remember this when you are doing your own forecasting. It is common for unforecasted weather events to effect our snow stability. This review of last weeks discussion will be the ground work for the "micro" forecast topic over the weekend.
AS ALWAYS, THIS ADVISORY IS ONE MORE TOOL TO HELP YOU MAKE YOUR OWN DECISIONS IN AVALANCHE TERRAIN. It should be used along with your own snow stability assessments, knowledge of safe travel techniques, skill in mountain weather's effect on the snowpack, and avalanche rescue.
THE WINTER LION HEAD ROUTE IS OPEN. The route leaves from the Huntington Fire Road and has orange signs starting on the Tuckerman Ravine trail at roughly the 1.8 mile mark. It is a steep and challenging route. Crampons, an ice axe, and the ability to use them with skill are required for safe travel. Avalanche skills are always required to travel safely in the mountains. Be prepared to do your own stability assessments.
The John Sherburne ski trail has improved over the week with wind moving snow in here and there over the entire length of the trail. There are a few problem waterbars and rocks still hidden just under the new snow.
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