VALANCHE ADVISORY PUBLISHED ON DECEMBER 28, 2014: Issued by Nick Meyers at 6:11am AVALANCHE DANGER 1. LOW Above treeline 1. LOW Near treeline 1. LOW Below treeline LOW avalanche danger exists for all aspects and elevations. Human triggered avalanches are unlikely, but not impossible. Small, isolated wind slabs exist near and above treeline. Blowing snow has been visible in recent days from NW-N-NE winds on the upper mountain. In general, conditions on Mt Shasta are firm and very icy. A slip and fall on steeper terrain will result in a slide for life without ice axe/crampon/self-arrest skills. Be prepared and know how to use your equipment. DANGER SCALE: 1. LOW 2. MODERATE 3. CONSIDERABLE 4. HIGH 5. EXTREME Home AVALANCHE PROBLEM 1OVER THE NEXT 24 HOURS TYPE ASPECT/ELEVATION CHARACTERISTICS LIKELIHOOD SIZE LIKELY UNLIKELY LARGE SMALL DISTRIBUTION TREND WIDESPREAD ISOLATED More Dangerous SAME Less Dangerous DESCRIPTION LOW avalanche danger exists for all aspects and elevations. Human triggered avalanches are unlikely, but not impossible. Small, isolated wind slabs exist above treeline. Blowing snow has been visible in recent days from NW-N-NE winds on the upper mountain. NW winds will dominate for the next two days and one can expect strong winds above treeline. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard / predictable to unpredictable due to slab stiffness and spatial variability. Avoid avalanche terrain with recent wind deposits or choose slopes gentler than 30 degrees in steepness. Wind slabs tend to stabilize within a few days unless deposited on a persistent weak layer. Give runout zones a wide berth when natural avalanches are expected or when others may be traveling above you. Remotely triggered slides are possible during heavy wind loading events. Areas of wind blown powder. This shot taken at 9,000 feet in the Old Ski Bowl on 12.25.14 RECENT OBSERVATIONS Not to much new to report today. Conditions continue to remain the same overall: firm, icy slopes with pockets of wind packed powder and a few areas with softer wind blown snow. Wind slab stability has overall been very good. Numerous extended column tests in wind slabs above treeline yesterday resulted in no fractures/propagation within columns (ECTX). For climbers and expert skiers, the upper mountain is unexplored territory. My intuition tells me that most of the snow available for transport has simply blown away, though I would not rule out the chance of finding small pockets of wind loading. Strong NW-N-NE winds have been visible over the past several days and NW winds will be very strong today and tomorrow. Of most concern will be if one slips and falls and fails to self arrest on steeper slopes. Know how to self arrest and be prepared for very cold temperatures and extreme wind chill over the week. Narrative from 12.27.14: Wind loading of leeward slopes and the formation of wind slabs is the current avalanche problem. That said, observations in the last 3 days have found these wind slabs to be stubborn to trigger. Observed slabs near and above treeline in the Old Ski Bowl and Gray Butte areas have been small, and about 10-35cm deep on top of the old snow. Skiers and snowmobilers recreating all over the mountain out of the Bunny Flat trailhead have reported no instability within slab layers. However... yesterday, stability tests within a 34cm wind slab on a south facing, low angle slope resulted in moderate failures (ECTN11/ECTN15 - Q2) about half way down the slab. Small facet growth (+/- 1mm) was observed at this weak layer, but numerous extended column tests could not produce full propagation. Based on this test and ski and snowmobile cuts on small convexities, full slope propagation within this weak layer seems unlikely. To sum this all up, medium to hard wind slabs on all aspects near and above treeline are isolated, small (6-12inches deep), and stubborn to trigger. The Mt Shasta snowpack took a big hit due to warm temperatures over Christmas week and weve seen upwards of 12 inches of settlement. Runnels in the snow as seen in photo below, not from rain, but simply from warm temps, have taken form all the way up to about 9,000 feet on the mountain. These formations are now rock solid and with cold temperatures becoming colder, they are likely here to stay until we receive more snow! As mentioned already, climbers and skiers venturing onto the upper mountain/steeper slopes of Mt Shasta should take note: the smooth, firm and icy conditions we are seeing currently have produced severe injury/fatality to climbers and skiers from slide for life, slips and falls. Self arrest and ice axe and crampon skills are mandatory to travel safely in said conditions. Be prepared and know how to use your equipment.
Posted on: Tue, 30 Dec 2014 02:47:28 +0000
Trending Topics
Recently Viewed Topics
© 2015