Monday December 31, 2018
Cornice Fall, Wind Slab
Travel & Terrain Advice
Past warm and wet conditions, followed by a rapid drop in freezing level and temperatures have rapidly changed the snow surface. Expect a supportive crust to be smooth and slippery. Ensure appropriate self arrest equipment when traveling in terrain and be cognizant of your location in terrain. Focus on an emphasis on terrain trap avoidance, example: sliding over steep terrain and cliffs.
Numerous Loose Wet avalanches observed and reported over the previous forecast period
Cornice growth in the alpine on north aspects continued and these features will be stubborn to human triggering. If trigger expect a cornice avalanche to be size 2 or greater. Take time to identify and avoid these features when travelling either above or below them.
In the upper alpine, expect to find wind slabs above 1600 meters. Located in areas specific to north aspect terrain, these avalanche problems will remain reactive to human triggering. If triggered, expect slab avalanches to be size 2 or greater
Warm and wet conditions followed by a cooling period have promoted the development of an upper rain crust. This rain crust is supportive to both foot and ski penetration. Above 1600 meters suspected wind slab development has occurred with precipitation amounts in excess of 50 cm and strong south westerly winds. Due to the warm temperatures, these upper snow pack instabilities are likely to be present but becoming less likely to human triggering. A crust can be found in the mid snow pack, buried around December 22nd and is currently non reactive. Below this a well settled and uniform snow pack is present.
|Surface||A supportive rain crust all aspects and elevations|
|Upper||moist and settling|
|Mid||A crust buried Dec 22 exists down up to 40 cm dependent elevation|
A powerful westerly flow pushed past to the south of the forecast area. Warm and wet conditions prevailed,with up-to 60mm of precipitation in westerns zones and the entire region seeing freezing levels rise to 1400 meters. The warm temperatures failed to linger and quit earlier than expected. In the wake of the storm a moderately strong ridge of high pressure flooded the region with cooling temperatures and clear sky.
A ridge of high pressure is scheduled to remain in the region until next year keeping the sky clear and temperatures and freezing levels low. Late Tuesday night the ridge is forecast to resign. Following this expect another wave of precipitation mid day Wednesday accompanied by warming temperatures and strong south west wind.
Posted on Monday December 31, 2018 by Jesse Percival