Aspen ===== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, cross loading, density, depth hoar, drifts, faceted, faceting, human triggered, low pressure, natural avalanche, orographic, slab, slabs, snow pit, sugar snow, trough, weak layers, wind loading, wind slab, wind slabs, wind transported, Mountain Weather and Avalanche Forecast for the Aspen Zone Forecast Issued on 12/26/2007 6:18:49 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 10-15 -3 to 2 0-5 Wind Speed(mph) 10-20 G30 10-20 10-20 Wind Direction WSW WSW NNW Sky Cover Increasing Overcast Overcast Snow(in) 0-1 1-3 0-2 Snowpack Discussion The fast moving waves of the past several days have brought changing wind directions. As a result you can expect to find areas of wind loading and cross loading on a variety of aspects near and above treeline. Light new snow and wind transported snow from the last few days are slowly adding a load to the old snowpack and it is becoming increasingly tender. On Monday, an observation from the Highlands Ridge noted one small natural avalanche and one skier triggered avalanche on E aspects near and above treeline. Only the upper layer in the snowpack, roughly 8 inches, was involved. A layer of faceted snow that made up the old surface was buried last Thursday. This layer may have been the cause of these new avalanches. Keep an eye out for it near and below treeline on most aspects. It will become more reactive as the load on it increases Above treeline, under this most recent storm snow, you will find a snowpack that is highly variable and made up of lots of old wind slab. This adds up to increasing complexity in the snowpack. On westerly aspects where the wind has reduced the snowpack depth, the cold temperatures will promote the faceting process. On northerly and easterly aspects, you will need to be thinking about deep slab instability. It may be difficult to trigger, but if you do, the avalanche could be large. You should avoid stout wind slabs on steep slopes. They will support your weight providing a false sense of security, but these slabs have the potential to be triggered from afar and often fracture above the point of initiation. A few observers have posed the question of how deep does the snowpack need to get before we don't have to worry about the sugar snow/depth hoar at the base. We know that the depth hoar eventually gets bridged over after a winters worth of snow. With very cold temperatures in the forecast, the best suggestion is to not trust it at this time of the year, as the depth hoar building process is firmly in charge, and the faceting process is staying ahead of these small storms we are getting. Route selection, travel habits, and awareness of the weak foundation will do more to keep you out of trouble than a bridge of snow. Also remember that the Colorado snowpack is notoriously variable. If you dig your snow pit in a deeper area, that weak layers at the base may not seem like a problem. A few turns down the slope however, where the snowpack is shallower, you might find very different conditions. We sure appreciate getting your observations on what you are seeing! Thanks. Avalanche Danger Above treeline the avalanche danger is CONSIDERABLE on North, Northeast, East, and Southeast aspects and MODERATE on other aspects. Danger is an overall MODERATE at and below treeline. Unstable wind slabs and drifts are likely today on many steep slopes above treeline, and possible on steep slopes near treeline. On many aspects and elevations, two weak layers of faceted snow exist. One at the base of the snowpack from October snows, and one just under the new snow. Both of these layers will make human triggered avalanches possible to probable today. Please drop us a quick e-mail with your avalanche, snowpack, or weather observations from this area or any other. Front Range =========== Current Keywords: CONSIDERABLE, LOW, MODERATE, avalanche danger, density, depth hoar, human triggered avalanches, low pressure, orographic, slab, slabs, snowpit, trough, wind loaded, wind slabs, Mountain Weather and Avalanche Forecast for the Front Range Zone Forecast Issued on 12/26/2007 6:17:39 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 12-17 -3 to 2 2-7 Wind Speed(mph) 10-20 G35 10-20 G30 10-20 Wind Direction W WSW NNE Sky Cover Increasing Overcast Overcast Snow(in) 0 0-2 1-3 Snowpack Discussion About 1-2" of new snow fell west of the Continental Divide, and heavier amounts fell east down to the Plains. The cold temperatures over the last week have not helped our snowpack. In near and above treeline areas, wind slabs rest on fragile depth hoar. The wind slabs have increased in hardness and depth this week, and the depth hoar continues to weaken. We've received reports of 5 to 20 cm thick depth hoar layers pouring out of snowpit walls. This sounds like bad news, but to make things worse...it is inconsistent. Conditions vary over fairly small areas. As you move though the backcountry you end up staying on the snow surface at times and then go crashing through to the ground. The weak snow that formed in October remains buried below our recent wind fall. These layers tend to remain quiet for weeks before letting you know they are still around. We are slowly stacking more snow on these weak basal layers. The slabs are now strong enough to let you travel into an exposed position before they fracture and create a dangerous hard-slab avalanche. Plan your routes carefully, cross exposed slopes one at a time and know your escape route before you need it. Avalanche Danger The avalanche danger for the Front Range zone is CONSIDERABLE on northwest, north, northeast, east, southeast and south aspects near and above treeline. Human triggered avalanches are probable on steep, wind loaded slopes. On southwest, and west, aspects near and above treeline the danger is MODERATE. Below treeline the danger is MODERATE on northeast to southeast aspects and otherwise LOW. Grand Mesa ========== Current Keywords: CONSIDERABLE, avalanche danger, density, faceted, human triggered avalanches, low pressure, orographic, trough, whumpfing, wind loaded, Mountain Weather and Avalanche Forecast for the Grand Mesa Zone Forecast Issued on 12/26/2007 6:20:43 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 15-20 0-5 3-8 Wind Speed(mph) 10-20 10-20 10-20 Wind Direction SSW SW -> N N Sky Cover Increasing Overcast Mostly Cloudy Snow(in) 0-1 2-4 0-1 Snowpack Discussion Reports from the Grand Mesa are few and far between, but there has been over 16" of new snow since Monday. The new snow fell on surface hoar in many areas and this could cause some problems. Avalanches that slide on the old snow surface are likely in steep and wind loaded areas. Approach steep slopes with caution and watch for signs of instability such as avalanches, cracking in the snow or whumpfing sounds. Cold temperatures and light snow in the forecast will hold the avalanche danger at current levels. 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, cross-loaded, crusts, density, faceted, low pressure, natural avalanche, naturals, orographic, powder , slab, slabs, trough, Mountain Weather and Avalanche Forecast for the Northern San Juan Mountain Zone Forecast Issued on 12/26/2007 6:30:53 AM Forecaster: Mark Rikkers Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 12-17 -3 to 2 0-5 Wind Speed(mph) 10-20 10-20 10-20 Wind Direction WSW SW N Sky Cover Increasing Overcast Overcast Snow(in) 0-1 3-5 0-2 Snowpack Discussion The Northern San Juans picked up between 3 and 10" of new snow on Christmas Day! The temperatures have been cold and the northerly winds relatively calm, making for light snow and great holiday powder turns. Reports of natural avalanche activity have been coming in steadily this past week, though a majority of the slides have involved only shallow upper snowpack slabs and have not been particularly large. A two-foot deep hard slab was observed above treeline on the west face of Red 3 near Red Mt. Pass on Monday. Across the street in upper Commodore Basin, a one-foot deep soft slab released out of high east-facing terrain. Shallow naturals were observed on cross-loaded southerly slopes above treeline near Red Mt. Pass, in the Ophir valley and on Engineer Mountain in the past few days. The stability pattern within our snowpack remains complex, and with many small shots of snow in the forecast this will not change anytime soon. Deep instabilities persist on cold, shady aspects where some of the "best" snow can be found. Sunnier aspects have been developing surface crusts during clear weather between periods of snowfall, creating complicated layers within the snowpack. Due to the cold weather recently, faceted snow has been forming on the surface and evidence of it can be found at all elevations and on all aspects. The wind direction will be switching around a bit over the next 36 hours, and more snow is in the forecast, so keep your eyes open for changing conditions and loading patterns. We have been slowly but steadily increasing the load on our snowpack and this means that the number of places you can trigger an avalanche are increasing as well. December has been a remarkable month for snow this year and backcountry travelers have been getting some world-class turns in as a result. Remember to respect the snowpack, and don't get complacent! Good route finding skills are key and keep using smart backcountry protocol - one avalanche could ruin your holiday. Avalanche Danger The avalanche danger for the Northern San Juan is 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, density, low pressure, natural, orographic, trough, Mountain Weather and Avalanche Forecast for the Southern San Juan Mountain Zone Forecast Issued on 12/26/2007 7:49:32 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Wednesday Night Thursday Temperature(°F) 15-20 0-5 7-12 Wind Speed(mph) 10-20 10-20 10-20 Wind Direction SW SSW N Sky Cover Increasing Overcast Overcast Snow(in) 0-1 3-5 0-2 Snowpack Discussion Around 2-4" of snow has fallen during the past 24 hours. One natural avalanche was reported from a steep south facing slope on Engineer Mountain. No other activity has been reported. There are some weak layers buried in the snow in the Southern San Juans, but without a significant new load they haven't been causing any problems. The zone will pick up small amounts of snow over the next few days, so be mindful of the increasing load. Most areas will remain stable, but you don't want to let your guard down and wander into an isolated pocket of instability. It only takes one avalanche to ruin your holiday. 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, cross-loading, density, faceting, facets, human triggered avalanches, low pressure, orographic, powder , settled, stabilized, trough, weak layers, wind slabs, Mountain Weather and Avalanche Forecast for the Sangre De Cristo Zone Forecast Issued on 12/26/2007 6:26:00 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 13-18 0-5 7-12 Wind Speed(mph) 10-20 G30 10-20 10-20 Wind Direction WSW SW NNE Sky Cover Increasing Overcast Overcast Snow(in) 0 0-2 4-6 Snowpack Discussion The Sangre zone has likely received new snow from the last couple systems, but we have received no observations indicating how much. Fresh wind slabs and cross-loading are possible on most open aspects. In neighboring zones, non-wind affected areas below treeline have settled and stabilized, but you may still find weak layers lurking on north and easterly aspects. You will find the most suspect slopes above treeline on N-NE-E aspects where a combination of wind slabs sits on top of low-density powder or facets. Cold temperatures have returned on Saturday which will promote the base layer faceting process where the snowpack is relatively shallow. Cold temperatures and several possibilities for snow are in the five-day forecast further complicating the snowpack. You should cautiously work into steeper terrain gradually, reevaluating the snowpack often. 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, density, depth hoar, drifting, faceted, low pressure, orographic, paths, slab, starting zones, stress, trough, wind slabs, Mountain Weather and Avalanche Forecast for the Sawatch Range Zone Forecast Issued on 12/26/2007 6:27:47 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Wednesday Night Thursday Temperature(°F) 10-15 0-5 2-7 Wind Speed(mph) 10-20 G30 10-20 10-20 Wind Direction W WSW NNE Sky Cover Increasing Overcast Overcast Snow(in) 0 1-3 0-2 Snowpack Discussion About 2-4" of new snow has fallen during the past 24 hours across the Sawatch zone. The primary stability concerns remain near and above treeline where deep slab instability exists on NW-NE-SE aspects. In these areas, wind slabs have formed on weak surface snow layers. The snow at the bottom of the pack is also quite weak. If you trigger a shallow slide that steps down, or on a deeply buried layer, it will ruin your hoilday. The only reports of activity have been a controlled release near Monarch Pass on an east aspect, slightly above treeline and yesterday rummors of a snomobile triggered slide came in from the northern border of the zone (south western Vail/Summit zone). It occurred on a north east aspect above tree line. Lack of reporting activity may be because visibility has been poor from blowing snow or activity is just not being reported. Regardless, the snow pack structure is trying to balance the stress of new or blowing snow and strength; which is decreasing, due to all the faceted growth. Faceting is much more rapid in shallow snow, like the starting zones of avalanches that have already run this year. We often see paths that slide early in the season reload and run on depth hoar again. Other suspect terrain would be areas where there are fresh, soft wind slabs. Approach these newly loaded areas with caution. 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. Watch for steep slopes with cross-loading or drifting. Below treeline the danger is LOW on all aspects. Steamboat ========= Current Keywords: CONSIDERABLE, avalanche danger, crusts, density, depth hoar, human triggered, low pressure, orographic, trough, weak layers, Mountain Weather and Avalanche Forecast for the Steamboat and Parks Range Zone Forecast Issued on 12/26/2007 6:17:04 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 10-15 -3 to 2 2-7 Wind Speed(mph) 10-20 G30 10-20 G30 5-15 Wind Direction WSW WSW N Sky Cover Increasing Overcast Overcast Snow(in) 0-2 1-3 0-2 Snowpack Discussion Portions of the Steamboat zone picked up over 15" of new snow since Monday. There are some very weak snow layers buried in the Steamboat snowpack. In addition, some weak layers have been forming on the surface over the last week. This means there are several potential sliding layers and avalanches in the new snow may step down into old snow layers, if you're really unlucky. Our observer on Rabbit Ears Pass found a Rutschblock score of 2 at the interface of the storm snow and older snow surface (about 8-12" down) on east and north aspects. He found about 6" of depth hoar on north aspects. The best approach is to stay conservative as you suss out the situation. The stability may change dramatically over a short distance as you change aspects or move into areas that avalanched over the last month. The most suspect areas are steep north or east-facing slopes. There are also some buried crusts on south facing slopes, so make sure to poke around on these aspects before you travel across a large, exposed slope. We hope to get some more observations from elsewhere around the Steamboat zone over the next week. If you have any please feel free to pass them along. Avalanche Danger The avalanche danger in the Steamboat zone is CONSIDERABLE. Natural avalanches are possible and human triggered slides are probable on steep exposed slopes. 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, denser, density, faceted, faceting, facets, human triggered, low pressure, natural, orographic, powder. , slab, slabs, trough, wind drifted, wind slabs, wind-loaded, windslabs, Mountain Weather and Avalanche Forecast for the Vail and Summit County Zone Forecast Issued on 12/26/2007 7:48:59 AM Forecaster: John Snook Weather Synopsis The next storm has started to enter the state on Wednesday afternoon. Light snow will spread from west to east across most mountain areas late Wednesday afternoon into Wednesday evening. Low pressure will cross the state on Thursday, and may close off for a short time over southern Colorado. Only light snow is expected Wednesday night. Following trough passage Thursday morning, the winds will shift to north allowing favored northern aspects to receive some more light, low density snow. Temperatures will be very cold and hence moisture is rather limited. Fortunately winds will remain on the light side. For Thursday night and beyond, persistent west to northwest flow will continue to provide periods of orographic snow into the weekend. Timing is difficult, but light snow may continue overnight Thursday, and then another shot for Friday night into Saturday. Weather Wednesday Night Thursday Thursday Night Temperature(°F) 10-15 -3 to 2 0-5 Wind Speed(mph) 10-20 G30 10-20 10-20 Wind Direction WSW WSW N Sky Cover Increasing Overcast Overcast Snow(in) 0 0-2 0-2 Snowpack Discussion Early reports this morning suggest 1-2" of new snow during the past 24 hours. The snowpack throughout the zone has become more complex and the snowpack on easterly aspects above treeline is the most complicated. Small faceted layers, larger basal facets intermixed with denser or harder wind slabs are common. Near treeline the surface snow is faceting and forming the so-called recycled powder. These surface layers are not a problem while they remain on top of the snowpack. New snow and wind drifted snow, however, have begun to cover these layers and form a new slab. If you trigger an avalanche in these new snow layers they might release a dangerous avalanche in the deeper layer. Although reports of slab avalanche activity have slowed, avalanches have been releasing every day. All of the human triggered reports; one near East Vail and the the other near Freemont Pass, were not expected and also quite large. A natural slide also occurred on an east aspect above treeline in the 10-Mile Range. If you venture into the backcountry over the next few days, continue to practice safe travel techniques. Ride one at a time, spot each other and have escape routes planned. Do not forget to stop once in a while to actually feel for layers in the snowpack. The structure changes with aspect and elevation. Triggering an avalanche will remain possible to probable and the consequences will be severe. Cold temperatures and light snow in the forecast suggest that the avalanche danger will hold at current levels. Avalanche Danger The avalanche danger for the Vail Summit zone is CONSIDERABLE on north through east through south aspects above treeline and on north through south-east aspects at treeline. Unstable slabs are probable on steep, wind-loaded terrain. The danger is MODERATE on other aspects above treeline and at treeline, where windslabs are possible on steep slopes. Below treeline, the danger is MODERATE on NE, E and SE aspects and otherwise LOW.