Regular avalanche forecasts with avalanche danger ratings have ended. We will continue to post all observations so please keep submitting them as you get out in the mountains. We will issue updates with any new snow that falls through the end of April.
During the spring we typically deal with three different avalanche problems:
1. Wet snow: Get out early and get home early. Get off of--and out from underneath--any slope approaching 35 degrees or steeper when the snow becomes wet enough to not support your weight.
2. New snow: We almost always get several winter-like snow storms in April and May. Treat each storm just like you would in winter. Avalanches can occur within the new snow typically from 1) low density layers deposited during the storm, 2) high precipitation intensity during a storm and 3) when cold, dry snow becomes wet for the first time, it almost always means wet sluffs (loose snow that fans outward as it descends). This can happen within minutes of direct sun on cold snow.
3. Wind Drifted Snow: Wind can rapidly load snow onto steep slopes making those slopes more prone to avalanching. Wind drifted snow looks rounded and pillowy, in some cases it can sound hollow like a drum. Be sure to check upper elevation wind sites in the links below to get an idea of what the winds have been up to.
Lastly - Glide Avalanches. These are an isolated issue and usually occur in areas where the snow rest on smooth rock slabs. The release of a glide avalanche is unpredictable, but it is usually preceded by the opening of a visible glide crack. The main way to avoid these slides is simply avoid being under slopes with a large glide crack.
For each storm it will be worth looking at the winds to find out which direction that have blown from and what direction they will be blowing for the day. Wind can rapidly load snow onto steep slopes making those slopes more prone to avalanching. Wind drifted snow looks rounded and pillowy, in some cases it can sound hollow like a drum. If you see shooting cracks it's a sign you may of hit a wind slab.
When cold, dry snow becomes wet for the first time, it almost always means wet sluffs (loose snow that fans outward as it descends).
Larger wet slab avalanches can happen when melt water percolates through a layered, winter snowpack for the first time especially after 3 days of strong melting combined with no refreeze at night.
Luckily, wet avalanches usually don't last forever because over time, days or weeks, of percolating melt water, all the layers in the snow disappear and the snow becomes homogenous and dense, turning into a stable summer-like snowpack. Typically, this cycle of instability maturing into stability occurs first on the south facing slopes in early spring, then progresses to the east and west facing slopes in mid spring and finally by late spring, the upper elevation north facing slopes go through a wet avalanche cycle.
Finally, glide avalanches occur regularly in spring as the entire snowpack slides slowly on the ground like a glacier until they suddenly release into a full-depth avalanche. These occur regularly on steep rock slabs and occasionally on steep grassy slopes. Notorious glide avalanche locations include places Stairs Gulch or the rock slabs in Broads Fork, which you should always avoid in spring. Avoid crossing under any slopes with telltale glide cracks in the snowpack. Remember they come down randomly, even at night.
The bottom line for wet avalanches: Get out early and get home early. Get off of--and out from underneath--any slope approaching 35 degrees or steeper when the snow becomes wet enough to not support your weight. Warning signs may include:
Any of these signs mean it's time to head home, or at least change to an aspect with cooler snow. Remember, even "smaller" slides can be dangerous in high-consequence terrain, such as above a terrain trap, trees, rocks, cliffs or a long, large avalanche path. Plan your trip to have a safe exit back to the car.
We almost always get several winter-like snow storms in April and May. Treat each storm just like you would in winter. Avalanches can occur within the new snow typically from 1) low density layers deposited during the storm, 2) high precipitation intensity during a storm and 3) from wind slabs created during the storm.
It's easy to test the new snow as you travel by jumping on small test slopes to see if they avalanche or just dig down with your hand to see how well the new snow is bonding. Snow can change dramatically in both space and time so never let your guard down. Especially avoid any steep slope with recent wind deposits, which are almost always dangerous.
Practice usual backcountry protocol, go one at a time, never travel above other people and practice all the usual risk reduction measures and low-risk travel ritual you learn in avalanche classes.
Updated Snow and Weather for April 23rd, 2020
This morning, under mostly cloudy skies mountain temperatures, are in the low 40s F at trailheads and mid-30s F at ridgelines. Winds are westerly and averaging 5-10 mph with gusts up to 20 mph at most elevations, at upper elevation ridgelines gusts are up to 30 mph. A trace amount of snow has fallen overnight.
Today, a weak disturbance will cross the range and bring periods of snow showers to the area. Mountain temperatures will be in the upper 30s F to low 40s F, winds will remain westerly averaging 20-30 mph with gusts up to 40 mph at the upper elevations. Snowfall totals could be between 1-3 inches of snow before Friday morning.
Snow surfaces in the backcountry have been described as "slide for life" the last few days, this means the new snow has a very firm surface to fall onto. A few inches of snow on a firm surface could lead to fast running sluffs today. While these fast running sluffs don't entrain much snow they can be dangerous in areas they could knock you off your feet and sweep you through complex terrain, or into terrain features where the shallow snow could pile up deeply.
See the full list of springtime avalanche problems below. This does not mean the end of avalanches. Spring storms and warm temperatures may make avalanche danger rise. If you scroll down, we provide some general avalanche advice to follow for typical spring weather patterns and we provide a series of other links you can use for current conditions and mountain weather.
Learn what to watch for during spring avalanche conditions when the snow becomes wet with this video from the UAC.
CLICK HERE FOR MORE GENERAL INFO AND FAQ
This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.
