Aspen ===== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, cross loaded, human triggered avalanches, low pressure, natural, natural avalanche, orographic, slab, slabs, trough, weak layers, wind slabs, Mountain Weather and Avalanche Forecast for the Aspen Zone Forecast Issued on 12/27/2007 4:00:37 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -13 to -8 5-10 -2 to 3 Wind Speed(mph) 5-15 10-20 G35 10-20 G35 Wind Direction NW W W Sky Cover Decreasing Increasing Overcast Snow(in) 0-1 0-1 1-3 Snowpack Discussion The Aspen Zone picked up another 1-2" of new snow on Thursday with light winds. A couple of new avalanches were observed on Wednesday. In Gold Dust Basin near the Peter Estin hut there was a small natural avalanche on a west aspect at about 12,200 ft. This looked to have run during the morning hours. Another natural slid on a NW aspect of Richmond Ridge at around 10500. This one occurred in steep terrain and looked to have run in old snow layers, deeper in the snowpack. The Aspen zone picked up another 1-2" of new snow on Thursday with light winds. Wind speeds will increase from the west on Friday. Expect to find new reactive soft slabs forming on exposed northeast through southeast aspects. These will form on top of a variety of older wind slabs and cross loaded slopes. Any steep wind loaded or cross loaded slope above treeline should be treated with caution right now. Human triggered avalanches will be probable in these areas. On north, northeast, and east aspects, deep slab instabilities must still be considered. This layer may be difficult to trigger, but if you do, the consequences will be a large avalanche. Multiple weak layers in the snowpack and a high degree of variability from one slope to the next require a cautious approach to backcountry travel. Frequent snowpack and weather observations will help you sort out the current conditions. Avalanche Danger Above treeline, there are pockets of CONSIDERABLE danger on steep wind loaded or cross loaded slopes facing north, northeast, east, and southeast. Danger is MODERATE on other aspects above treeline. The avalanche danger is an overall MODERATE at and below treeline. Please send us a quick e-mail to caic@qwest.net with your avalanche, snowpack, or weather observations from this area or any other. Those observations are very valuable to our forecasts. Front Range =========== Current Keywords: CONSIDERABLE, LOW, MODERATE, avalanche danger, avalanche hazard, depth hoar, drifted, faceted, human triggered, human triggered avalanches, low pressure, orographic, shovel, slabs, trough, wind scoured, wind slabs, Mountain Weather and Avalanche Forecast for the Front Range Zone Forecast Issued on 12/27/2007 4:08:20 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -8 to -3 5-10 0-5 Wind Speed(mph) 10-20 15-25 G45 15-25 G45 Wind Direction WNW W W Sky Cover Decreasing Increasing Overcast Snow(in) 0-Trace 0-Trace 0-2 Snowpack Discussion Another inch or two of new snow was added to the snowpack without much wind on Thursday. Our observer found in Butler Gulch a more supportable snow surface below treeline. Above treeline he found 1-3" of new snow on top of ugly wind slabs. The old Christmas snow was still breaking out in a few locations. Extremely variable conditions were found above treeline with some areas wind scoured down to rock and other regions loaded with thick wind slabs. Increasing west winds on Friday will start to move the new snow to easterly aspects. Expect to find new reactive soft slabs forming on east through southeast aspects above treeline. Fragile depth hoar continues to grow near the ground. An observer on the west side of Cameron Pass was able to trigger two slides with ski cuts that went to the ground on steep north facing aspects below treeline. The most suspect slopes continue to be north through east where the snowpack is most complicated with a combination of new snow, new and old wind slabs, and a weak, faceted base layer. I have tweaked the avalanche hazard levels slightly to reflect some of the more recent changes. Human triggered slides remain probable on north through east aspects especially where freshly drifted storm snow will not bond well with the older snow surface. The snowpack is highly variable. You will need to stay constantly alert to changes underfoot. This will require the use of your shovel to learn more about what you are riding on. Avalanche Danger The avalanche danger for the Front Range zone is CONSIDERABLE on north, northeast, east, and southeast aspects near and above treeline. Human triggered avalanches are probable on steep slopes with fresh wind pillows. On northwest, west, southwest, and south aspects near and above treeline the danger is MODERATE. Below treeline the danger is MODERATE on north to southeast aspects and otherwise LOW. Grand Mesa ========== Current Keywords: CONSIDERABLE, avalanche danger, faceted, human triggered avalanches, low pressure, orographic, slabby, surface hoar, trough, weak layer, whumpfing, Mountain Weather and Avalanche Forecast for the Grand Mesa Zone Forecast Issued on 12/27/2007 4:01:13 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -7 to -2 10-15 3-8 Wind Speed(mph) 0-10 5-15 5-15 Wind Direction N WSW WSW Sky Cover Decreasing Increasing Overcast Snow(in) 0-Trace 0-Trace 0-1 Snowpack Discussion Our observer on Grand Mesa found very cold temperatures and a couple inches of new snow since Wednesday. Winds speeds were starting to increase from the north to northwest creating a soft, slabby snow surface. He found a buried surface hoar layer about 8-12" underneath the recent storm snow. He was surprised to find no failures on this layer with column tests in several hasty pits. Nonetheless, he remained quite concerned about this layer and he indicated that he would not trust it. With cold temperatures and brisk winds in the forecast, I will not change the avalanche danger level. With a sufficient trigger, such as a snowmobile, it remains probable to start a slide on a weak layer. You need to approach steep slopes with caution and watch for signs of instability such as avalanches, cracking in the snow or whumpfing sounds. Avalanche Danger The avalanche danger in the Grand Mesa zone is CONSIDERABLE. Natural avalanches are possible and human triggered avalanches are probable. The most problematic areas are probably steep slopes that have weak faceted snow under new snow. If you have any observations or data to share, please send them to [57]caic@qwest.net. San Juan North ============== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, collapses, collapsing,, cross-loaded, faceted, facets, human triggered, low pressure, orographic, slab, slabs, trough, wind slabs, Mountain Weather and Avalanche Forecast for the Northern San Juan Mountain Zone Forecast Issued on 12/27/2007 4:01:36 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -12 to -7 5-10 0-5 Wind Speed(mph) 5-15 10-20 10-20 Wind Direction NNW W W Sky Cover Decreasing Increasing Overcast Snow(in) 0-1 0-1 0-1 Snowpack Discussion Reported avalanche activity has decreased slowly over the past several days. Observers are noting that the older, lower portion of the snowpack is very strong. Big collapses have not been heard for a while. The lower slab is also insulating the faceted base layer from the recent cold surface temperatures. One observer even noted slow strengthening of the base layer. This is Colorado and we should never ignore the possibility of deep slab instability, but evidence is suggesting that the chances for full depth avalanches are decreasing near and below treeline. Recent periods of wind, cold, and snow, however, have increased the complexity of the upper snowpack. Layers of storm snow, wind slabs, and buried facets all point to paying close attention to this portion of the pack. Observers are noting moderate column test failures at the interface between an 8-12" surface layer and a 4" faceted layer of older snow. Human triggered slides remain possible to probable primarily within these upper snowpack layers. We will need to monitor the upper snowpack closely as more snow load is added. For now, as you travel through the backcountry, continue to monitor for signs of instability such as cracking, collapsing, or recent slide activity. Remember to respect the snowpack and do not take it for granted! Get out there, but continue to use good route finding skills and smart backcountry protocol to keep safe through this holiday season. Avalanche Danger The avalanche danger for the Northern San Juan continues to be CONSIDERABLE on all slopes that are near and above treeline. Though some areas are scoured from recent winds, you will find unstable slabs on steep and cross-loaded slopes. Below treeline the danger is MODERATE. San Juan South ============== Current Keywords: LOW, MODERATE, avalanche danger, human triggered, low pressure, orographic, trough, weak layers, Mountain Weather and Avalanche Forecast for the Southern San Juan Mountain Zone Forecast Issued on 12/27/2007 4:02:03 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -7 to -2 10-15 3-8 Wind Speed(mph) 10-20 10-20 5-15 Wind Direction NW WSW SW Sky Cover Decreasing Increasing Overcast Snow(in) 0-Trace 0-Trace 0-Trace Snowpack Discussion Wolf Creek Pass received about 3" of new snow since Wednesday. There have been no reports of recent slide activity. Very cold temperatures are expected to last into Friday before starting to moderate. Our observer described the bottom portion of the snowpack as bomber. Recent snow and wind events plus cold temperatures have created a variety of layers in the upper snowpack. These include some buried weak layers, but without a significant new load they have not been causing large problems. Human triggered slides remain possible near and above treeline where the newer snow could move on top of the older stable layer. Most areas will remain stable, but you do not want to let your guard down and wander into an isolated pocket of instability. Avalanche Danger The avalanche danger is MODERATE on all aspects near and above treeline. Below treeline, the danger is LOW. Sangre de Christo ================= Current Keywords: CONSIDERABLE, avalanche danger, density, human triggered, human triggered avalanches, low pressure, orographic, slab, slabs, trough, wind slabs, Mountain Weather and Avalanche Forecast for the Sangre De Cristo Zone Forecast Issued on 12/27/2007 4:02:20 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -8 to -3 8-13 2-7 Wind Speed(mph) 5-15 10-20 G35 10-20 G30 Wind Direction NW WSW SW Sky Cover Decreasing Increasing Mostly Cloudy Snow(in) 0-Trace 0 0-Trace Snowpack Discussion The coldest temperatures of the season so far are possible Friday morning. We have received no observations from the Sangre zone, but it is likely that at least several more inches of snow have accumulated across the zone. Winds have been relatively light, but it will not take much to move the recently fallen low-density snow. You should watch for fresh wind pillows that could be covering older wind slabs on steep exposed slopes. Human triggered slides within the more recent storm snow layers are probable. You should also be aware of the possibilities for deep slab instabilities on N-NE-E aspects. A combination of fresh wind pillows, older wind slabs, and a weak base layer could avalanche large with a sufficient trigger. You should constantly evaluate the snowpack for changing conditions. Avalanche Danger The avalanche danger in the Sangre de Cristo zone is CONSIDERABLE. Natural avalanches are possible and human triggered avalanches are possible. Please send observations from this or any other zone to [57]caic@qwest.net Sawatch ======= Current Keywords: CONSIDERABLE, LOW, MODERATE, avalanche danger, cross-loading, drifting, faceted, facets, low pressure, orographic, shovel, slab, slabs, sugar snow, trough, wind slab, Mountain Weather and Avalanche Forecast for the Sawatch Range Zone Forecast Issued on 12/27/2007 4:02:37 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -10 to -5 5-10 0-5 Wind Speed(mph) 5-15 10-20 G35 15-25 G35 Wind Direction NW W W Sky Cover Decreasing Increasing Overcast Snow(in) 0-1 0-1 1-3 Snowpack Discussion Another inch or two of new snow was added to the Sawatch zone snowpack without much wind on Thursday. Temperatures are expected to stay cold through Friday, and increasing west winds will start to move the new snow to easterly aspects. Expect to find new reactive soft slabs forming on northeast through southeast aspects above treeline. The recent cold temperatures have allowed the older snow grains to grow into facets or sugar snow - a process that is progressively weakening the snowpack. The new snow and new wind slab is not bonding too well to the old surface. Test results reveal two main issues. The first is in the upper half of the snowpack where a grain size difference exists from one layer of sugar snow to the next. The second is the growing concern of larger faceted grains near the ground. So the picture is new snow and growing wind pillows sitting on a weakening mid-pack sitting above a weakening deep slab instability issue. Not a pretty picture. The snowpack is highly variable. You will need to stay constantly alert to changes underfoot. This will require the use of your shovel to learn more about what you are riding on. Avalanche Danger The avalanche danger is MODERATE with pockets of CONSIDERABLE on northwest, north, northeast, east, and southeast aspects near and above treeline. The danger is MODERATE on all aspects at treeline and other aspects above treeline. Be especially cautious on steep slopes with cross-loading or drifting. Below treeline the danger is LOW on all aspects. Steamboat ========= Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, faceted, human triggered, low pressure, natural, naturals, orographic, shovel, slabs, trough, Mountain Weather and Avalanche Forecast for the Steamboat and Parks Range Zone Forecast Issued on 12/27/2007 3:59:31 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -10 to -5 5-10 0-5 Wind Speed(mph) 5-15 10-20 G35 15-25 G35 Wind Direction W WSW WSW Sky Cover Decreasing Increasing Overcast Snow(in) 0-Trace 0-2 2-4 Snowpack Discussion An observer noted several natural slides on west aspects of Hahns Peak several days ago, but no naturals have been reported since. With careful route selection, a number of lines have been ridden without incident on east and southeast aspects of Hahns Peak. Recent storm snow has amounted to a few inches. Wind speeds are expected to increase from the west on Friday. Expect to find new reactive soft slabs forming on exposed northeast through southeast aspects. Based on limited information, I am lowering the avalanche hazard to MODERATE on northwest, west, southwest, and south aspects. Human triggered slides are still possible on these slopes. A weak, faceted base layer remains a concern on shady aspects. The combination of fresh wind pillows on top of the weak base layer will keep the danger level somewhat higher on north through southeast aspects. A conservative approach in the backcountry is still a healthy choice. The stability may change dramatically over a short distance as you change aspects. Use your shovel to find out what you are riding on. Avalanche Danger The avalanche danger in the Steamboat zone is CONSIDERABLE on north, northeast, east, and southeast aspects at all elevations. Human triggered slides are probable on steep exposed slopes with fresh wind pillows. The danger is MODERATE on northwest, west, southwest, and south aspects. 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, faceted, facets, human triggered avalanches, low pressure, orographic, shovel, slab, slabs, sugar snow, trough, wind slab, Mountain Weather and Avalanche Forecast for the Vail and Summit County Zone Forecast Issued on 12/27/2007 4:08:05 PM Forecaster: John Snook Weather Synopsis A low pressure trough is centered over Colorado at midday Thursday. As the trough axis passes winds will shift from south to north, and speeds will remain light. Periods of very light mountain snowfall are expected to linger into Thursday evening on favored north facing aspects, but accumulations will be generally less than an inch. Temperatures will drop well below zero by Friday morning. Winds will shift on Friday to west-northwest setting up favorable orographic flow. A lull in snowfall is expected for Friday morning. Mountain snowfall will increase later in the day as a series of weak short waves embedded in the northwest flow crosses the state through the weekend. Weather Thursday Night Friday Friday Night Temperature(°F) -13 to -8 3-8 -3 to 2 Wind Speed(mph) 5-15 10-20 G35 15-25 G35 Wind Direction NW W W Sky Cover Decreasing Increasing Overcast Snow(in) 0-1 0-1 1-3 Snowpack Discussion Another inch or two of new snow was added to the snowpack without much wind on Thursday. Temperatures are expected to stay cold through Friday, and increasing west winds will start to move the new snow to easterly aspects. Expect to find new reactive soft slabs forming on northeast through southeast aspects above treeline. The recent cold temperatures have allowed the older snow grains to grow into facets or sugar snow - a process that is progressively weakening the snowpack. The new snow and new wind slab is not bonding too well to the old surface. Test results reveal two main issues. The first is in the upper half of the snowpack where a grain size difference exists from one layer of sugar snow to the next. The second is the growing concern of larger faceted grains near the ground. So the picture is new snow and growing wind pillows sitting on a weakening mid-pack sitting above a weakening deep slab instability issue. Not a pretty picture. The snowpack is highly variable. You will need to stay constantly alert to changes underfoot. This will require the use of your shovel to learn more about what you are riding on. Avalanche Danger The avalanche danger for the Vail-Summit zone is CONSIDERABLE on north, northeast, east, and southeast aspects near and above treeline. Human triggered avalanches are probable on steep slopes with fresh wind pillows. On northwest, west, southwest, and south aspects near and above treeline the danger is MODERATE. Below treeline the danger is MODERATE on north to southeast aspects and otherwise LOW.