Avalanche Advisory Archive Pre-2016
| Date Issued: | 2013-12-15 |
|---|---|
| Danger: | 2 |
| Trend: | 5 |
| Probability: | 0 |
| Size: | 2 |
| Problem: | 0 |
| Discussion: | ...WINTER WEATHER ADVISORY THROUGH 5 AM... TODAY...SNOW SHOWERS. SNOW ACCUMULATION 2 TO 6 INCHES. HIGHS TONIGHT...SNOW SHOWERS. SNOW ACCUMULATION 2 TO 6 INCHES. STORM MONDAY...SNOW SHOWERS. SNOW ACCUMULATION 1 TO 2 INCHES. HIGHS It has been a wild and wooly week for our snowpack. All the fresh snow from mid-week has seen over an inch and a half of water put on top of it. Widespread natural avalanches cleaned out many of our paths mid-cycle helping to reduce the hazard from large slides. But to the best of my knowledge Behrends and the White Path have not seen even small releases yet this year. Cooling temps bring a decreasing hazard trend regarding the deeper weak layers, but new snow and wind will create an increasing hazard for smaller new slabs. Temperatures in the start zones dropped below freezing about 7pm last night and have continued to drop through early this morning. Mt Juneau is about -5C, with Mt Roberts at -2C and Eaglecrest the coldest at -7C. The largest avalanche problem that we face today is new wind/storm slabs that could step down through the melt-freeze crust from last night and entrain some of the loose unsolidated colder snow from mid-week. Even these moderate size slides are unlikely to pose problems for Behrends, White, and Thane Rd slide paths. However they could be large enough to hit the Flume Trail or Perseverance. Tonight with potentially more than a foot of new snow in the start zones and moderate winds for transport danger from these new slabs will be increasing. Definitely a good idea to stay off of the Flume and Perseverance Trails later today and use due caution under all avalanche terrain. |
| Tip: | PRECIPITATION & TEMPERATURE Precipitation In the assessment of an avalanche threat, the amount of precipitation in combination with wind, temperature and the existing old snowpack constitute a central factor. Whether the amount of snow in a snowfall period (1-3 days) is to be assessed as critical or rather unproblematic, depends on the conditions during and immediately after the snowfall. An amount of 10-20 cm of fresh snow, fallen with strong wind exposure at low temperatures on an old layer of melt-freeze crust can have a highly critical impact. On the other hand, fresh snowfall of 30 cm fallen on a wet layer with no wind and at a temperature of around 0?C at the beginning constitutes no significant increase in risk. Altitude and temperature profile during the precipitation have different effects on the avalanche situation, so this must be critically assessed. Temperature One of the basic conditions to be observed during and after the snowfall is the temperature. Cold, hot air, and sunlight considerably affect the transformation processes in the snowpack and thus also the avalanche situation. Both the exact temperature itself as well as the temperature trend affect snow bonding in either a positive or negative way. Considerable warming leads to very critical situations, but its impact can be well assessed. Quick Warming -- Slow, moderate warming promotes the settling of the snowpack and therewith the binding between the layers. Slow Warming + Warming during the day and cooling at night causes an ideal solidification of the snowpack, but an aggravation of the avalanche situation must be taken into account due to solar radiation during the day from E to W. Warming during the day, cooling at night ++ Cold preserves existing hazards and delays the settlement. Cold - Persistent, severe cold promotes the formation of floating snow (ball bearing effect) and surface hoar (covered by a critical weak layer of snow), resulting in a worsening of the situation. Strong Persistent Cold -- |
| Forecaster: | Chris Eckel |