Aspen ===== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, creep, cross loaded, crown, crowns, dense, density, depth hoar, drifting, drifts, faceted, facets, high pressure, human triggered, natural avalanches, slab, slabs, test slopes, weak layers, wind drifting, wind loaded, wind loading, wind slabs, windslabs, Mountain Weather and Avalanche Forecast for the Aspen Zone Forecast Issued on 1/2/2008 6:58:52 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 20-25 15-20 25-30 Wind Speed(mph) 10-20 10-20 15-25 Wind Direction WSW WSW WSW Sky Cover Partly Cloudy Partly Cloudy Mostly Cloudy Snow(in) 0 0 0 Snowpack Discussion Observers around the Aspen Zone found the new windslabs slabs to be quite tender. Monday a skier triggered a soft slab avalanche just below Pearl Pass, on the Crested Butte side. It was on an ESE aspect at around 12,700 feet. The crown of the avalanche was up to two feet deep. Control work popped out soft slabs on Monday, too, on southeast aspects near treeline with crowns 1-2 feet deep. Observers found slabs up to 1ft thick on east aspects that were very reactive to a skier's weight. These slabs cracked and propagated up to 30 ft away on short test slopes. An observer in Ashcroft on Monday reported continuous loading on Green Mountain. The upper half of the snowpack there consisted of dense snow from recent wind deposition resting on a base of weak facets and depth hoar. The most concerning results in a test pit here were the basal weak layers. Strong and sustained winds out of the southwest, west, and northwest blasted the peaks at the end of the year. Terrain at and above treeline has seen significant effects from this wind, as well as some open and exposed areas below treeline. You will encounter widespread hard slabs, soft slabs, cross drifting, and plenty of "wind jacked" snow near and above treeline. Any steep wind loaded or cross loaded slope at any elevation should be treated with caution right now. In many areas these fresh drifts are resting on some older facets or lower density snow that made up the old surface. This strong over weak layering will make natural avalanches possible and human triggered ones probable. Lots of fresh wind slabs, multiple weak layers in the snowpack, and a high degree of variability from one slope to the next demand a cautious approach to backcountry travel. Expect to find very sensitive wind slabs and drifts in the backcountry. Avoid traveling on or below steep exposed slopes, particularly in near and above treeline areas. Light snow and intense wind loading added a lot of load to the snowpack. This means that the potential for full depth avalanches is slowly creeping back into the picture. These facets and depth hoar grains at the base of the snowpack will be the failure layer. A smaller slide that initiates in upper snowpack weaknesses may step down to these older layers. The most suspect areas for these full depth avalanches continues to be north through east facing slopes where the snowpack is most complicated with a combination of new snow, new and old wind slabs, and a weak, faceted base layer. Avalanche Danger The avalanche danger for the Aspen Zone is CONSIDERABLE on all aspects near and above treeline. Natural avalanches are possible and human triggered ones probable at these elevations. Steep slopes with fresh wind slabs should be avoided at this time. Below treeline in open or exposed areas, expect to find pockets of CONSIDERABLE danger on slopes 35 degrees and steeper that have seen recent wind drifting. In all other areas below treeline, danger is MODERATE. Clear skies will allow us a good look around the backcountry for the next couple days and we would love to know what you are seeing. Avalanche forecasting is a community effort. Help out your fellow backcountry travelers (and forecasters) by dropping us a quick e-mail at caic@qwest.net with any avalanche, snowpack, or weather observations you might have. Front Range =========== Current Keywords: CONSIDERABLE, Human triggered avalanches, MODERATE, cross loaded, cross loading, drifted, drifting, drifts, high pressure, human triggered avalanches, natural, path, rutschblock, sastrugi, slab, slabs, sublimating, windloaded, windslab, windslabs, windward, Mountain Weather and Avalanche Forecast for the Front Range Zone Forecast Issued on 1/2/2008 7:11:30 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 20-25 12-17 22-27 Wind Speed(mph) 10-20 15-25 15-25 Wind Direction W W W Sky Cover Mostly Clear Partly Cloudy Mostly Cloudy Snow(in) 0 0 0 Snowpack Discussion A great report came in from Loveland Pass from Tuesday. A party was touring on the north side of the Pass, and witnessed a snowbaorder trigger a large avalance on an east-southeast aspect above treeline. The snowboarder "turned directly into the center of the path. He made 6 to 8 turns, probably 2/3 to 3/4 down the slope, when the entire slope fractured... he was dead center of a large slab...He disappeared behind a knoll as the slab broke apart and began to run. Fortunately, he popped out below the knoll as the debris began to pile up." The avalanche started in a new windslab, then stepped down to an icy layer close to the ground. The avalanche was up to 6 feet deep and about 300 feet wide. The touring party was getting rutschblock scores of 1 and 2. This is a great example of UNSTABLE SLABS on steep windloaded terrain, and that HUMAN TRIGGERED AVALANCHES ARE PROBABLE. (This was a great example with no injuries, we got through the holiday with just a couple close calls and no fatalities in Colorado, and I can release some tension). There were several human triggered avalanches over the weekend, including two close calls. On Monday a snomobiler triggered a slide on Gravel Mountain, west of Grand Lake. The avalanche was triggered on an east aspect above treeline, and it completely buried the rider. Fast action on the part of a nearby group rescued the buried snowmobiler in a few minutes. Sunday, a skier triggered and was caught in an avalanche in the Indian Peaks near Eldora Ski Area. The avalanche was on a windloaded north northeast aspect at treeline. There were several skier triggered avalanches reported from the Berthoud Pass area on Friday and Saturday, again on windloaded north to east aspects. Control work brought down slides on north, east, southeast, and west aspects on Monday as well, some breaking 6 feet deep and running as far as 2,500 feet. Observers are still tallying up the natural activity, but southerly aspects above treeline were particularly active in the Vail Summit zone. It was difficult to measure snow with so much wind, but about 6 to 12 inches fell in the Front Range Zone during the last storm. Relentless westerly and northwesterly winds blasted the peaks, redistributing both new and existing snow and significantly altering the snow surface. Near and above treeline, most of the storm snow, and most of the old snow, was scoured off windward faces. The snow went somewhere--some sublimating off to Kansas--but most of the snow was drifted and loaded. You will encounter widespread hard slabs, cross drifting, and plenty of "wind jacked" sastrugi near and above treeline. Westerly aspects and wind exposed spots will be scoured to the ground. Expect to find areas of heavy loading and cross loading on slopes facing north through east through south. Some areas are stripped down to the rock, grass or Avalanche Danger The danger is CONSIDERABLE on north, northeast, east, southeast and south aspects near and above treeline. Human triggered avalanches are probable on steep slopes with windslabs, drifts, or pillows. There are pockets of CONSIDERABLE danger on cross loaded terrain features on southwest, west and northwest aspects near and above treeline. Below treeline the danger is MODERATE. Human triggered avalanches are probable on steep wind-effected terrain below treeline. Grand Mesa ========== Current Keywords: avalanche danger, collapsing,, drifted, drifts, high pressure, weak layer, windslabs, Mountain Weather and Avalanche Forecast for the Grand Mesa Zone Forecast Issued on 1/2/2008 6:33:18 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 28-33 15-20 28-33 Wind Speed(mph) 0-10 5-15 5-15 Wind Direction SSW SSW SW Sky Cover Partly Cloudy Partly Cloudy Mostly Cloudy Snow(in) 0 0 0 Snowpack Discussion Strong winds raked the whole state the end of last year and the Mesa was not spared. Winds were generally west and northwest and transported lots of snow. Look for areas of loaded and drifted snow on north through east to southeast aspects. The windslabs and drifts may not bond well with the old snow underneath, and could react to the weight of a backcountry traveler. Be aware of changes in the snow while you travel in the backcountry today. It may be easy to go from a relatively safe spot to a dangerous one with just a few steps. Watch for obvious signs of instability including recent avalanching, cracking, collapsing, and hard over weak layering. Avoid traveling on or below steep exposed slopes today. Avalanche Danger We have insufficient data to rate the avalanche danger in the Grand Mesa Zone. Please send observations from this or any other zone to [57]caic@qwest.net San Juan North ============== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, crusts, drifting, drifts, faceted, faceting, high pressure, naturals, slab, slabs, starting zones, windslabs, Mountain Weather and Avalanche Forecast for the Northern San Juan Mountain Zone Forecast Issued on 1/2/2008 6:13:26 AM Forecaster: Mark Rikkers Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 22-27 15-20 28-33 Wind Speed(mph) 5-15 5-15 5-15 Wind Direction SSW S SW Sky Cover Mostly Cloudy Mostly Cloudy Mostly Cloudy Snow(in) 0 Tr 0-1 Snowpack Discussion Observers reported avalanches on most aspects from Sunday, Monday, and Tuesday. West, north, northeast, southeast, and south aspects all had activity. On Sunday a skier triggered an avalanche on a northeast slope just above treeline near Lake City - the skier was not injured. High southerly aspects have been particular active, with several naturals running from north winds loading snow onto south-facing sun crusts. Almost all of the recent avalanche activity has been confined to the upper snowpack, with fractures generally a foot deep. There was one significant exception: near Telluride, a large hard slab avalanche released on a northeast aspect well above treeline that was 4 feet deep, 1000 feet wide and ran 1500 feet vertical to the ground. This is a good reminder that the snowpack has persistent weaknesses at the bottom, particularly on high northerly slopes. Deep, weak grains are capped with a solid slab that has the potential to produce destructive avalanches. There were ferocious northwest winds over the weekend. Windspeeds backed off a bit on Monday as they swung to the north with the ideal speeds for drifting snow into upper starting zones. Late Tuesday night, winds finally eased as they swapped back to a more southerly flow that is expected to continue through this week. The wind has been busy lately - observers near Telluride found new drifts more than 6 feet deep next to areas scoured back to tundra and dirt. Remember that wind not only redistributes large amounts of snow, it also breaks down snow grains and packs them together tightly, forming cohesive windslabs that have the potential to fracture above the point of initiation and propagate over long distances. On northerly terrain, deep slab instabilities continue to be a concern as weak snow at the base of the snowpack persists. On the sunnier aspects, the middle and upper snowpack is a mix of various layers of slabs and crusts sandwiched around faceted snow. Recent cold temperatures accelerated the faceting process within and at the surface of the snowpack, causing layers of snow grains to become angular and cohesionless. These layers, however thin, are weak and do not bond well with new snow. As we look ahead at another storm system coming our way at the end of this week, it would be wise to remember that these layers are there. Today will be the warmest day in a long time - expect some loose activity as the snow surface heats up, particularly on steep, sunny slopes with exposed rocks. Avalanche Danger The avalanche danger for the Northern San Juan zone is CONSIDERABLE on all aspects near and above treeline. Below treeline the danger is MODERATE on all aspects. Be particularly careful on steep, convex, San Juan South ============== Current Keywords: MODERATE, avalanche danger, avalanche path, drifted, drifts, high pressure, slabs, starting zone, surface hoar, weak layer, weak layers, wind transport, windloaded, windslab, windslabs, Mountain Weather and Avalanche Forecast for the Southern San Juan Mountain Zone Forecast Issued on 1/2/2008 6:49:58 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 28-33 18-23 30-34 Wind Speed(mph) 5-15 5-15 5-15 Wind Direction SSW SSW SSW Sky Cover Partly Cloudy Mostly Cloudy Mostly Cloudy Snow(in) 0 Tr 0 Snowpack Discussion Observers on Wolf Creek Pass reported good conditions Tuesday. They did spot one recent avalanche in the Hourglass, a northerly facing avalanche path below treeline. The slide ran about 2 feet deep on a convex roll low in the starting zone. On easterly aspects, the observers found moderate stability test results on a surface hoar layer about 8 inches below the surface. There was another layer of surface hoar about 16 inches down that had hard but clean test results. The hard-and-clean result could indicate a fairly stubborn weak layer that can fracture into a wide avalanche. The surface hoar, and other buried weak layers, will be worth considering before committing to steep terrain. The last storm did not add a significant amount of snow, but strong and sustained westerly winds accompanied the snowfall. There was lots of wind transport. Expect to find drifted and windslabbed snow near and above treeline on north through east to southeast aspects. Human triggered slides remain possible near and above treeline on steep slopes with fresh slabs or drifts. Use caution on and near steep slopes with fat wind pillows, soft drifts, and the classic hard windslabs with a hollow sound. Today will the the first really warm day in a while. Expect to see the snow surface warming rapidly. Wet loose activity will occur on steep, sunny slopes as the snow warms up. Avalanche Danger The avalanche danger is MODERATE on all aspects and elevations. Unstable slabs are possible on steep, windloaded terrain. Sangre de Christo ================= Current Keywords: avalanche danger, crossloaded, drifted, high pressure, whumpfing, wind slabs, windward, Mountain Weather and Avalanche Forecast for the Sangre De Cristo Zone Forecast Issued on 1/2/2008 6:32:44 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Wednesday Night Thursday Temperature(°F) 25-30 5-10 27-32 Wind Speed(mph) 15-25 15-25 15-25 Wind Direction SW SW W Sky Cover Partly Cloudy Partly Cloudy Partly Cloudy Snow(in) 0 0 0 Snowpack Discussion We have received no observations from the Sangre zone. The Sangres got lots of winds and missed out on the snow that fell elsewhere. Strong and persistent westerly winds scoured high elevation windward slopes and deposited the snow onto easterly aspects. Winds drifted snow low onto northeast, east, and southeast slopes. Gullies and other terrain features on a variety of aspects will be crossloaded as well. Beware of wind slabs and pillows on steep slopes. Evaluate the snowpack frequently and look for obvious signs of instabilty including whumpfing, cracking, or recent avalanching. Avalanche Danger We have insufficient data to rate the avalanche danger in the Sangre de Cristo Zone. Please send observations from this or any other zone to [57]caic@qwest.net Sawatch ======= Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, collapsing , drifted, drifting, faceted, faceting, high pressure, human triggered avalanches, sastrugi, slab, slabs, sublimating, sugary, windslabs, windward, Mountain Weather and Avalanche Forecast for the Sawatch Range Zone Forecast Issued on 1/2/2008 6:33:50 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Wednesday Night Thursday Temperature(°F) 25-30 15-20 28-32-3 Wind Speed(mph) 10-20 10-20 15-25 Wind Direction SW W W Sky Cover Partly Cloudy Mostly Clear Mostly Cloudy Snow(in) 0 0 0 Snowpack Discussion The southern Sawatch picked up as much as 17 inches of snow out of the last storm. Not bad, but the real story was the winds. Strong and sustained westerly winds blasted the peaks. Near and above treeline, most of the storm snow, and most of the old snow, was scoured off windward faces. The snow went somewhere--some sublimating off to Kansas--but most of the snow was drifted and loaded. You will encounter widespread hard slabs, cross drifting, and plenty of "wind jacked" sastrugi near and above treeline. Westerly aspects and wind exposed spots will be scoured to the ground. The new slabs are sitting on older snow that faceted during last year's cold spell. The cold temperatures drove the faceting process, resulting in lots of weak, sugary snow. Not the best foundation to put big, ugly slabs on top of. You will find some wind effected snow below treeline on north, northeast, east, and southeast aspects. It is the same problem of windslabs on top of weak faceted snow, but the slabs may be softer and offer better riding conditions. Out of the wind, the storm snow can still form a slab, if the old snow underneath is especially faceted. The softer slabs can be sneaky, because they do not feel like slabs or much of an avalanche problem. Carefully evaluate the snowpack well before you get onto or underneath steep slopes. Watch for obvious signs of instability including recent avalanching, cracking, collapsing and stronger over weaker layering. Wednesday will be the first warm, sunny day in a while. Expect some wet loose activity from steep, sunny slopes below treeline. Avalanche Danger The avalanche danger is CONSIDERABLE on all slopes near and above treeline, and on north, northeast, east, and southeast aspects below treeline. Human triggered avalanches are probable on steep slopes with fresh windslabs. On other aspects below treeline the danger is MODERATE. Steamboat ========= Current Keywords: , CONSIDERABLE, avalanche danger, collapsing, cross loaded, crust, faceted, high pressure, human triggered avalanches, natural avalanches, powder , slab, slabs, stress, weak layers, windslab, Mountain Weather and Avalanche Forecast for the Steamboat and Parks Range Zone Forecast Issued on 1/2/2008 6:34:16 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 15-20 10-15 22-27 Wind Speed(mph) 5-15 10-20 15-25 Wind Direction WSW WSW W Sky Cover Partly Cloudy Partly Cloudy Mostly Cloudy Snow(in) 0 0 0 Snowpack Discussion Up to 2.5 inches of water (25 to 35 inches of snow)last weekend in favored locations in the Steamboat Zone. A good storm, but the real story is the wind. Strong westerly winds accompanied the snow, rapidly loading easterly slopes. Observers noted natural avalanches in the Oak Creek Canyon Group and on the Sleeping Giant. Fractures ranged from 2 to 4 feet deep, and the slides ran up to 900 vertical feet. The strong winds formed extensive windslab, even in the trees. Under the slabs and new snow are weak, faceted grains that will not readily bond to the overlying slabs. There are some other weak layers, too. Observers near the ski area found easy to moderate stability test results on a thin crust that is now buried about 3 feet below the surface. This is a perfect depth to be triggered by backcountry riders--close enough to the surface to be impacted by the additional stress of a rider, but deep enough to stay in place by itself, and deep enough to cause an unpleasant-sized avalanche. Human triggered slides are probable, particularly on north to east aspects today. You can expect to find the most reactive slabs on exposed northeast through southeast aspects, although winds blew so hard that pockets of slab formed even in thick trees. Look for wind pillows and cross loaded terrain features. While slides will not likely step down into the weak layers at the base to the snowpack, it remains a possibility. Don't let powder fever get the best of you! Use conservative decision making in the backcountry. Carefully evaluate the snowpack well before you get onto or underneath steep slopes. Watch for obvious signs of instability including recent avalanching, cracking, collapsing and stronger over weaker layering. Avalanche Danger The avalanche danger in the Steamboat Zone is CONSIDERABLE on all aspects and elevations. Unstable slabs are probable on steep slopes. Human triggered avalanches are probable in steep terrain. If you have any observations or data to share, please send them to [57]caic@qwest.net. Vail ==== Current Keywords: CONSIDERABLE, LOW, MODERATE, avalanche danger, collapsing , creep, crossloaded, drifting, facet, faceted, faceting, facets, high pressure, human triggered, natural avalanches, paths, sastrugi, slab, slabs, sugary, wind slabs, windloading, windward, Mountain Weather and Avalanche Forecast for the Vail and Summit County Zone Forecast Issued on 1/2/2008 6:59:21 AM Forecaster: Spencer Logan Weather Synopsis It is high pressure, and the weather is quiet. There are broken clouds scudding across the skies this afternoon. Clouds will thicken this evening, spreading from the Four Corners northeastward. Skies will be cloudy Thursday ahead of the next storm. The San Juans might wring out a few scattered snow showers. The storm comes in early Friday morning on southwesterly flow that favors the southern mountains. The weather will remain unsettled all weekend, with the heaviest snow on Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 20-25 12-17 25-30 Wind Speed(mph) 10-20 10-20 15-25 Wind Direction SW SW W Sky Cover Mostly Clear Partly Cloudy Mostly Cloudy Snow(in) 0 0 0 Snowpack Discussion With the clearing weather, observers have been taking stock of the avalanche activity during and after the storm. There were two close calls in the Front Range Zone (more information in the Front Range forecast). There were natural avalanches on most aspects above treeline, with southerly and crossloaded paths particularly active. Control work triggered avalanches on north, east, southeast, and west aspects, some breaking 6 feet deep. Snow accumulations from the last storm were 7-15 inches. Not bad, but the real story was the winds. Strong and sustained westerly winds blasted the peaks and reshaped the snowscape. Most slopes, regardless of aspects or elevation have some kind of wind effected snow on them. Near and above treeline, most of the storm snow, and most of the old snow, was scoured off windward faces. The snow went somewhere, and you will encounter widespread hard slabs, cross drifting, and plenty of "wind jacked" sastrugi near and above treeline. Westerly aspects and wind exposed spots will be scoured to the ground. The new slabs are sitting on older snow that faceted during the last cold spell. The cold temperatures drove the faceting process, resulting in lots of weak, sugary snow. Not the best foundation to put big, ugly slabs on top of. There will be two instability issues to look out for. First is the continued facet growth near the ground. Full depth avalanches have crept back into the picture as the facets get bigger and weaker. The second issue is the newly formed wind slabs on the surface. Hard slabs act like sleeping tigers. It is easy to creep closer to them while they are sleeping, but you do not want to wake them up. Be very mindful of where you get cracking. Hard slabs tend to not crack too much until you are near the edges of the slab, then they zipper open with lightning speed. Watch for obvious signs of instability including recent avalanching, cracking, collapsing and stronger over weaker layering. Avoid traveling on or below steep exposed slopes above treeline. Human triggered slides are probable above treeline on north through east to south aspects with recent windloading. Avalanche Danger The avalanche danger in the Vail Summit Zone is CONSIDERABLE above treeline on north, northeast, east, southeast, and south aspects. The danger is MODERATE on other aspects above treeline. Near treeline the danger is MODERATE on all aspects. Below treeline the danger is MODERATE on north, northeast, east, southeast, and south aspects, and LOW on other aspects.