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Thursday, May 31, 2018 at 2:11 PM Issued by: Spencer Logan  

Spring and Summer Avalanche Safety

Avalanches are possible any time you find snow on steep slopes in Colorado. Although accidents are less likely in the summer, there have been fatal avalanche accidents every month of the year. Below is general avalanche safety advice for the late spring and summer. Our next scheduled update is November 1, 2018. We issue updates if we anticipate unusually dangerous conditions before then.

Weather Discussion

We have stopped issuing weather forecasts for the 2017-18 season. You can get current weather forecasts from the National Weather Service.

Our computer Model Forecasts update four times a day and will run through the summer. If you are going into the Colorado high country, you can use our Weather Stations page to check current conditions. 

Avalanche and Snowpack Discussion 

Avalanches are possible in the mountains of Colorado whenever you find snow on a steep slope. In general, you should consider the consequences of being caught in an avalanche before you cross any steep, snow-covered slope, but below are some avalanche problems you may encounter over the summer. We will update the Field Reports as information comes in, so please send us your observations.

Storm Slabs, Wind Slabs, and Loose-Dry Avalanche 

Most avalanches happen during or right after a snowstorm. Later in the spring and throughout the summer, snowstorms are less likely. However, every time new snow falls and the wind moves it through the terrain, these avalanches are possible. New snow layers often have a hard time sticking to hard, icy surfaces, so a summer snowstorm can produce many small avalanches if it falls onto old snow. Even small avalanches are dangerous if they can push you off a cliff, or into rocks, trees, or a gully. The best way to manage these avalanches in the summer is to have a current weather forecast, recognize when there is enough new snow to produce storm avalanches, and select terrain that minimizes your exposure to the risk. Avoid areas where there was old snow under the recent snow, wind pillows along ridgelines, and cross-loaded features like rock outcrops and subridges.

Wet Slab and Loose-Wet Avalanches

As the snow heats up and begins to melt, water moving through the snowpack can produce avalanches. Watch the overnight low temperatures at high-elevation weather stations, but remember that air temperature, cloud cover, and wind all affect how the snow freezes each night. Regardless of what wet avalanche you are worried about, remember to stay off and out from under steep snow-covered slopes when you start to sink into the wet snow more than about 6 inches.

The most common wet avalanches are loose, sluff or point-release avalanches. These are most dangerous if they can push you off a cliff, or into rocks, trees, or a gully. 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 slushy. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches 

Wet Slab avalanches are much more dangerous. These often occur when melt water when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). The snow conditions that produce wet slab avalanches last longest on high-elevation, northerly slopes as we move into summer. Look at the old snow layers to see if they are still dry or turning to coarse springtime snow. In many cases, snow conditions are poor when Wet Slabs are a significant problem. Most people leave the mountains or find places with firmer, less slushy snow and away from the slopes where Wet Slabs are a problem. Avoid terrain where and when you suspect Wet Slab avalanches. Give yourself a wide safety buffer to handle the uncertainty

Cornice Fall

Throughout the winter, strong winds build large overhanging snow features along ridge lines. These cornices can break off at any time of year, but periods of significant temperature warm-up during the spring are times to be particularly aware. Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridge line areas with cornices. Avoid areas underneath cornices. If your route goes under one, use a similar approach as wet slab avalanches, look for a good overnight freeze, and try to get past them early in the day. Remember that the sun may hit them earlier than it hits the slopes below them.

  • Wind loading & small slab avalanche (full)
  • Cornices breaking off in summer snow. (full)
  • A small Loose Wet avalanche out of steep and rocky terrain. (full)

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Avalanche Observations
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Field Reports
Report Date Observer Snowpack Obs Avalanches Media

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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Bear Lake Sat Jul 21 5:00 AM 57 - - - - -
Bottle Peak Sat Jul 21 5:50 AM 55 47 9 285 10 -
Cameron Pass Sat Jul 21 5:00 AM 57 34 3 186 6 0.4
Grand Mesa - Skyway Point Sat Jul 21 7:00 AM 52 63 5 165 10 15.5
Kendall Mt Sat Jul 21 6:00 AM 47 66 5 209 10 -
Molas Pass Sat Jul 21 6:00 AM 49 76 1 245 3 -
Vail Pass - Cdot Yard Sat Jul 21 6:00 AM 46 70 1 101 2 -
Wolf Creek Pass Sat Jul 21 6:00 AM 52 65 8 212 10 -
Monarch Pass (050e200) Sat Jul 21 6:54 AM 50 64 6 180 6 -
Columbus Basin Sat Jul 21 5:00 AM 52 - - - - -
Lizard Head Pass Sat Jul 21 5:00 AM 47 - - - - -
Medano Pass Sat Jul 21 6:00 AM 60 - - - - -
Mesa Lakes Sat Jul 21 6:00 AM 58 - - - - -
Ripple Creek Sat Jul 21 6:00 AM 54 - - - - -
Slumgullion Sat Jul 21 6:00 AM 52 - - - - -
Schofield Pass Sat Jul 21 6:00 AM 48 - - - - -
Storm Peak Observatory Sat Jul 21 6:10 AM 57 47 2 228 2 -
Taylor Park Sat Jul 21 5:57 AM 42 100 4 315 5 -
Wolf Creek Summit Sat Jul 21 6:00 AM 54 - - - - -
Zirkel Sat Jul 21 6:00 AM 56 - - - - -

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