Avalanche Advisory Archive Pre-2016
The National Weather Service Forecasts-
TODAY...MOSTLY CLOUDY. PATCHY FOG EARLY IN THE MORNING. SCATTERED RAIN SHOWERS...POSSIBLY MIXED WITH SNOW IN THE MORNING IN THE MENDENHALL VALLEY. HIGHS AROUND 41. LIGHT WINDS BECOMING SOUTHEAST 10 MPH.
TONIGHT...DECREASING CLOUDS. SCATTERED RAIN SHOWERS IN THE
TUESDAY...PARTLY CLOUDY. PATCHY FOG IN THE MORNING. HIGHS AROUND 41. NORTHEAST WIND 10 TO 20 MPH.
Temperatures cooled off a bit last night. Yesterday the Mt Roberts Tram had a high of 43f. Eaglecrest saw a high of 40f at mid mountain as well. This should have allowed the 3\" of snow from the previous day to settle out and bond a bit somewhat increasing stability in the shallow slabs that were in place.
Currently its 32f at the tram summit and 29f at Mid mountain at Eaglecrest.
The precipitation started around 9pm last night. We picked up 4.3mm at the Tram and 7.4mm at Eaglecrest. The first part started as rain at that elevation but by partway through the rain temps had fallen below freezing. This left about 3cm of new snow at both locations. You can assume you have a little more at upper elevations.
This snow came in quite wet.
Todays forecast calls for warmer temps and not much in the way of precipitation.
Look to see wet loose avalanches at mid to lower elevations where this wet new snow doesn't want to bond well to the old snow. The steeper pitches may want to clean themselves as the temps warm up. It might not take much in the way of a ski cut or snow falling off of trees and rocks to start these wet loose slides.
At upper elevations you want to be looking for areas with increased sensitivity from this new snow being added to the previous shallow windslabs that exist in isolated locations.
If we see significant warming or sun look for these wet loose slides to occur at upper elevations as well.
Danger is MODERATE to considerable today. With not much precipitation or wind in the forecast natural avalanches are possible but would be mostly wet loose avalanches at lower elevations with not much size to them. Human triggered avalanches also remain possible. Once again with not much size to them but you may see both slab avalanches at the uppermost elevations and wet avalanches closer to and below the snow line.
Enjoy a nice day.
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
How they form
Loose Wet avalanches form in new snow or old surface snow that is warming. Warming temperatures, strong solar radiation, or rain-on-snow make the surface snow damp or wet. As the water content increases, the snow becomes unconsolidated. They start at a point and entrain additional snow as they move down hill, and have a characteristic fan-like shape.
Where they are
Loose Wet avalanches form at or near the snowpack surface. Like Loose Dry avalanches, most Loose Wet avalanches start on very steep slopes. If a Loose Wet avalanche entrains a very large amount of snow, it can run long distances on low-angled terrain. They can form on any aspect. Because they are often associated with solar radiation, they are most common on sun-exposed slopes.
In Colorado, Loose Wet avalanches are most likely in the late winter and early spring. Loose Wet avalanches are usually problematic for a period of hours at a time. There may be a daily cycle, as the sun warms the snow surface and makes Loose Wet avalanches more likely. The potential for Loose Wet avalanches can increase rapidly. Because they are often associated with solar radiation, the aspects where Loose Wet avalanches are likely can change through the day as the sun moves east to west.
There are many clues that Loose Wet avalanches are likely. Monitor the snowpack surface for a layer of wet, slushy snow more than several inches deep. Water may be visible between the ice grains. On small, very steep test slopes, the surface layers will slide easily. Fresh roller balls?little snowballs?falling off trees and cliff bands indicate that the snowpack surface is getting weak.
Treatment and Avoidance
Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches. Sluff management in extreme terrain is an effective technique for skilled riders. Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Monitor the snowpack surface, and move to colder, shadier slopes once the slush layers form
LIVE TO RIDE ANOTHER DAY!
Eaglecrest is hosting an Backcountry Safety Awareness and Companion Rescue Course Saturday March 5th from 8:30am-3:30pm.
This course is free and sponsored by the Department of Public Safety.
During this day long course you will learn about avalanche terrain, weather, and stability assessment tests. You will also learn about Avalanche Rescue as well as transceiver, probe and shovel use.
Please share this offering with your friends. Lets all do out part to maintain a safe backcountry community.
For more information or to sign up please email Tom.Mattice@juneau.org