Aspen ===== Current Keywords: CONSIDERABLE, HIGH, avalanche danger, cross loaded, density, faceted, facets, human triggered avalanches, low pressure, natural, precipitation , settled, slabs, wind loaded, wind slabs, Mountain Weather and Avalanche Forecast for the Aspen Zone Forecast Issued on 12/10/2007 6:29:25 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Night Tuesday Tuesday Night Temperature(°F) 20-25 7-12 17-22 Wind Speed(mph) 10-20 G30 10-20 G30 10-20 G30 Wind Direction SW SSE SE Sky Cover Increasing Overcast Mostly Cloudy Snow(in) 1-3 1-3 0-2 Snowpack Discussion Many areas of the Aspen zone have received in excess of 3 feet of snow during the most recent storm cycle, which is a big load of new snow in a short period of time. Most of the snow fell with warm temperatures and has settled well. Colder temperatures returned late Saturday and the last 6" of snow was of lighter density. West and then southwest winds strengthened enough on Sunday to start moving the snow onto lee N-NE-E-SE aspects. Recent slide activity has been correlated to slopes on northerly aspects that contain a weak base layer of facets that formed within pre-existing old snow. These same slopes are now gaining an additional load of fresh wind blown snow. There is considerable tension within tender slabs where slides have not already occurred. There is potential for full depth slides in these areas that contain wind slabs with a weak, faceted base layer. Snow pits may not show all concerns as we still have a highly variable early season snowpack. The big picture probably will. That picture includes the addition of over three feet of new snow, and now, wind strong enough to form slabs. For now, extra caution will be required if you are traveling in the backcountry, especially near and above treeline. Avalanche Danger The avalanche danger in the Aspen Zone is rated at HIGH above treeline on W-NW-N-NE-E aspects. At treeline we are at CONSIDERABLE with pockets of HIGH on any any wind loaded or cross loaded W-NW-N-NE-E slope. Above treeline on SE-S-SW aspects the danger is CONSIDERABLE. Below treeline the danger is rated CONSIDERABLE on all aspects. Fresh wind slabs near and above treeline will require extra caution if you travel anywhere near them. Both natural and human triggered avalanches are likely in these areas. Your backcountry observations are VERY important to us. Observations can be submitted to [59]caic@qwest.net. Front Range =========== Current Keywords: CONSIDERABLE, HIGH, MODERATE, avalanche danger, collapsing,, density, faceted, lee , low pressure, precipitation , wind loaded, Mountain Weather and Avalanche Forecast for the Front Range Zone Forecast Issued on 12/10/2007 6:27:51 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Night Tuesday Tuesday Night Temperature(°F) 22-27 7-12 20-25 Wind Speed(mph) 10-20 G35 10-20 10-20 Wind Direction WSW S SE Sky Cover Increasing Overcast Mostly Cloudy Snow(in) 0-1 1-3 1-3 Snowpack Discussion About 6" of lower density snow fell at the end of the most recent storm cycle. We have received a variety of observations this weekend with mixed signals. Our observer near Berthoud Pass found signs of instability much reduced from Friday to Sunday at elevations near and below treeline. On the hand, winds on Sunday strengthened from the northwest and then backed to southwest overnight to start moving the low density snow onto lee NE-E-SE aspects. Where snowfall was not on the ground prior to last week, generally on W-SW-S-SE aspects, signs of instability have been minimal. On other aspects (NW-N-NE-E), we have received many reports of collapsing, cracking, and recent slide activity. Several large slides have been observed that initially ran on the interface between the recent storm snow and last week's storm snow, but then stepped down through the faceted base layer to the ground. One such slide was noted on Saturday above Lost Lake in a N facing chute near Eldora Mountain Resort. Other such large slides have been noted near Berthoud Pass. These slides have occurred on slopes with two common snowpack features - wind affected and a weak, faceted base layer that formed from older snow. I am lowering the avalanche danger to CONSIDERABLE on NW-N-NE-E aspects below treeline, and to MODERATE on other aspects. But the danger level remains at HIGH where wind effects are most prevalent on near and above treeline NW-N-NE-E aspects. Human triggered avalanches remain likely on these slopes. Avalanche Danger The avalanche danger for the Front Range zone is HIGH on NW-N-NE-E aspects near and above treeline and CONSIDERABLE below treeline. Human triggered avalanches are probable to likely on steep slopes that contain a weak base layer and are wind loaded. Elsewhere, the avalanche danger is MODERATE. Grand Mesa ========== Current Keywords: MODERATE, avalanche danger, facets, low pressure, precipitation , settled, Mountain Weather and Avalanche Forecast for the Grand Mesa Zone Forecast Issued on 12/10/2007 6:32:50 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Night Tuesday Tuesday Night Temperature(°F) 27-32 17-22 25-30 Wind Speed(mph) 5-15 5-15 10-20 G35 Wind Direction S E SSE Sky Cover Increasing Overcast Overcast Snow(in) 0-2 4-6 4-6 Snowpack Discussion Natural avalanche activity was reported across the Grand Mesa on Friday, some of these brought down quite a bit of snow. All of the reported activity came from steep north aspect terrain. We have not received any reports since then. Most of the snow fell with warm temperatures and has likely settled well. In neighboring zones, most recent slides have occurred within a snowpack containing a weak base layer of facets that formed from older snow. Most of the Grand Mesa zone did not have snow cover prior to the last two storm cycles. Human triggered avalanches remain possible on steep slopes containing large amounts of recent storm snow. Snow in the forecast will likely trend the danger upward by Tuesday. Avalanche Danger The avalanche danger for the Grand Mesa zone is overall MODERATE. Your backcountry observations are VERY important to us. Observations can be submitted to [59]caic@qwest.net. San Juan North ============== Current Keywords: CONSIDERABLE, HIGH, avalanche cycle, avalanche danger, avalanche hazard, cross-loading, dense, faceted, facets, high pressure, low pressure, natural, natural avalanche, paths, precipitation , settle, slab, slabs, suncrusts, Mountain Weather and Avalanche Forecast for the Northern San Juan Mountain Zone Forecast Issued on 12/10/2007 6:30:03 AM Forecaster: Mark Rikkers Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Night Tuesday Tuesday Night Temperature(°F) 22-27 17-22 20-25 Wind Speed(mph) 10-20 G35 10-20 G30 15-25 G40 Wind Direction S SSE S Sky Cover Overcast Overcast Overcast Snow(in) 3-6 3-6 3-5 Snowpack Discussion Yesterday was a beautiful day and there was great visibility for the first time in a while. Backcountry travelers and snow safety teams were out in force, and the reports of natural and triggered avalanche activity continue to come in. Dozens of slides have been reported, particularly from the Ophir and Telluride area. Most, but not all, of these slides occurred on northerly aspects near and above treeline and some of the details are impressive. Both hard and soft slabs have been observed, with fracture lines ranging up to 8-feet deep! The recent snow, particularly during the beginning of the recent storm, was dense and quickly formed very cohesive slabs. This cohesiveness creates the potential for extensive propagation in slab avalanche releases. Observations of natural and triggered avalanches confirmed this, with reports of several wide fracture lines spanning distances up to 500 feet. While we have received observations of avalanches on most aspects, the areas that have been most active and continue to be of particular concern are northerly (NW-N-NE) aspects at all elevations. These slopes have a combination of heavy recent storm snow sitting above relatively weak, faceted snow grains at their base. East and west aspects developed suncrusts and associated near-surface facets during the recent period of high pressure between storms and relatively fresh slabs are testing that interface. Southerly aspects still have relatively little snow in them but high winds caused cross-loading on certain southerly paths during the recent storm and caused some significant releases, particularly in the Red Mt. Pass area. As of yesterday, our natural avalanche cycle was effectively over and the avalanche hazard was steadily decreasing as the snowpack got a chance to settle out with a 24-hour period of sun and calm, precipitation-free weather. However, we are already seeing the start of another storm with the potential for decent snow totals, particularly on the south sides of Red Mt. and Lizard Head Passes. We have a complicated snowpack that requires respect and continual evaluation as you tour in the backcountry - have fun out there, but be careful. Avalanche Danger The avalanche danger is HIGH on NW-N-NE aspects at all elevations. On E and W aspects, the danger is CONSIDERABLE all elevations. On SE-S-SW San Juan South ============== Current Keywords: CONSIDERABLE, HIGH, cross loaded, explosive, low pressure, natural, natural avalanche, precipitation , surface hoar, water equivalent, weak layers, wind slabs, Mountain Weather and Avalanche Forecast for the Southern San Juan Mountain Zone Forecast Issued on 12/10/2007 6:33:45 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Monday Night Tuesday Temperature(°F) 25-30 20-25 25-30 Wind Speed(mph) 10-20 10-20 G30 10-20 G30 Wind Direction SSW S SSW Sky Cover Overcast Overcast Overcast Snow(in) 8-10 5-7 7-9 Snowpack Discussion Wolf Creek Pass received a storm total of 49 inches, and a melted water equivalent of 6.7". The snow that has fallen from the last two storm cycles has been heavy and wet. Generally this points to a good bond to underlying snow surfaces, but, there are buried weak layers like surface hoar that will have a very hard time supporting this new load. Wind speeds have been strong enough to move the new snow, and these have generally been from the southwest and then south. Several natural and explosive triggered avalanches from near and below treeline have been reported recently from this zone, generally on E and NE aspects plus cross loaded south facing slopes. A sizeable natural avalanche ran across Highway 160 on the west side of Wolf Creek Pass Saturday morning. Visibility and accessibility above treeline have been limited at best, so few observations from these elevations. Although signs of instability are slowly decreasing with time, the forecast calls for more heavy snow through Tuesday. This will add a new load onto a snowpack with buried weak layers and fresh wind slabs. All indications continue to point toward an unstable snowpack, we are advising a lot of extra caution the next few days. Avalanche Danger The danger rose is good visual representation of a complex avalanche danger across the Southern San Juan. We are at HIGH danger near and above treeline on N-NE-E aspects. CONSIDERABLE with pockets of HIGH near and above treeline on W-NW aspects and on SE aspects. Below Sangre de Christo ================= Current Keywords: avalanche danger, crusts, facets, low pressure, precipitation , settled, sugary, whumpfing, wind slabs, Mountain Weather and Avalanche Forecast for the Sangre De Cristo Zone Forecast Issued on 12/10/2007 6:34:59 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Monday Night Tuesday Temperature(°F) 23-28 20-25 23-28 Wind Speed(mph) 10-20 10-20 10-20 Wind Direction SSW SSE SE Sky Cover Mostly Cloudy Overcast Overcast Snow(in) 1-3 4-6 4-6 Snowpack Discussion Most of the recent storm snow fell with warm temperatures and has likely settled well. In neighboring zones, recent slides have occurred within a snowpack containing a weak base layer of facets that formed from older snow. The storm snow has been falling on a variety of snow surfaces including sun crusts, weak sugary snow and hard wind slabs. The new snow will easily slide on the hard surfaces. On shady aspects where the weak base layer exists, slides could step down into the older snow to create larger, more destructive avalanches. Be particularly watchful for signs of instability such as cracking, whumpfing, and recent avalanche activity. It is likely that avalanche danger has fallen somewhat, but keep your guard up on N-E aspects where wind slabs and a weak base layer may exist. Snow in the forecast could reverse the danger trend to upward by Tuesday. 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 [59]caic@qwest.net Sawatch ======= Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, lee , low pressure, precipitation , settled, Mountain Weather and Avalanche Forecast for the Sawatch Range Zone Forecast Issued on 12/10/2007 6:36:43 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Monday Night Tuesday Temperature(°F) 22-27 15-20 20-25 Wind Speed(mph) 10-20 10-20 10-20 G30 Wind Direction SW SE E Sky Cover Mostly Cloudy Overcast Overcast Snow(in) 2-4 2-4 3-5 Snowpack Discussion The heavy wet snow has settled out quickly. Our observer around Monarch Pass indicated a surprisingly stable snowpack. Many observers have noted an uncharacteristic lack of wind during the past few days which thus far has been the main missing ingredient from an increasing avalanche danger point of view. This factor will need to be monitored closely. Westerly and then southwesterly winds strengthened enough on Sunday to start moving snow onto lee N-NE-E-SE aspects. Locations where old snow is buried underneath the recent storm snow are the most likely places to find signs of instability. As mentioned in previous discussions, the southern portion of the Sawatch zone had very little remaining old snow prior to the past week's storms where avalanche danger somewhat lower than in the northern portion of the zone. Enjoy the new snow, but carefully evaluate your routes, avoid terrain traps and just practice safe travel habits. Snow in the forecast will likely trend the avalanche danger upward by Tuesday. Avalanche Danger The avalanche danger is MODERATE with pockets of CONSIDERABLE on NW-N-NE-E aspects near and above treeline. Steamboat ========= Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, collapsing,, explosive, facets, human triggered avalanches, low pressure, precipitation , weak layer, Mountain Weather and Avalanche Forecast for the Steamboat and Parks Range Zone Forecast Issued on 12/10/2007 6:27:18 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Night Tuesday Tuesday Night Temperature(°F) 17-22 7-12 18-23 Wind Speed(mph) 10-20 10-20 10-20 Wind Direction SW NE ENE Sky Cover Increasing Overcast Overcast Snow(in) 0-1 1-4 2-6 Snowpack Discussion We have not received any new reports from the Steamboat zone since Thursday when avalanche mitigation work at the local ski area produced explosive and skier triggered avalanches on NW aspects. Ski area reports and automated observations suggest about 8" of new snow since Friday morning. In neighboring zones, avalanche activity has been reported from wind affected slopes that held snow prior to the last two storm cycles. These conditions are most likely found on high elevation NW-N-NE-E steep slopes. Other aspects had no snow on the ground before last weekend. Sunday temperatures were colder. Surface hoar may develop overnight if skies remain clear enough. Not a problem today, but could become a future problem as a buried weak layer. Colder temperatures will also promote the generation of facets in the base layer of the snowpack. Watch for signs of instability, such as collapsing, cracking, or recent slide activity on steep northerly aspects. Human triggered avalanches remain probable on these slopes. If you have any observations to share, please send them to [59]caic@qwest.net. Avalanche Danger The avalanche danger in the Steamboat Zone is CONSIDERABLE on NW-N-NE-E aspects. Elsewhere, the avalanche danger is MODERATE. Vail ==== Current Keywords: CONSIDERABLE, HIGH, MODERATE, avalanche danger, collapsing , density, depth hoar, faceted, human triggered, lee , low pressure, precipitation , ski cut, stress, weak layers, wind loaded, Mountain Weather and Avalanche Forecast for the Vail and Summit County Zone Forecast Issued on 12/10/2007 6:28:46 AM Forecaster: John Snook Weather Synopsis Southerly flow ahead of low pressure near Baja has already started to spin moisture into the southern mountains. Heavy snow is expected for areas favored by southerly flow including the San Juan south of Red Mountain Pass, the Grand Mesa, and the Flat Tops. A rather complicated pattern ensues as the Baja low gets ejected across Colorado on Tuesday while a second low pressure system drops south over the Great Basin to carve out a broad area of low pressure over the western US. The bottom line is unsettled mountain weather through Wednesday morning, including a period of upslope snow along the Front Range on Tuesday. Precipitation tapers off on Wednesday as low pressure moves east and winds shift to northerly. A return to northwest flow follows for the latter part of the week. Embedded pulses will generate periods of mountain snowfall favoring the northern and central mountains, especially during Thursday night. Weather Monday Night Tuesday Tuesday Night Temperature(°F) 20-25 7-12 17-22 Wind Speed(mph) 10-20 G35 10-20 G30 10-20 G30 Wind Direction WSW SSE SE Sky Cover Increasing Overcast Mostly Cloudy Snow(in) 0-1 1-3 0-2 Snowpack Discussion About 6" of lower density snow fell at the end of the most recent storm cycle. This weekend in the Vail Pass area, observers continued to find a very reactive snowpack, where collapsing and cracking were common on all aspects and elevations, including mid-slope fractures with lots of trees. Despite this, there were no reports of any avalanche involvement. An observer on Saturday touring on Baldy Mountain east of Breckenridge reported widespread collapsing and cracking on all aspects just below and above treeline. Well above treeline the snowpack was generally shallower. Our observer near Breckenridge on Sunday also noted significant cracking on northerly aspects near treeline. The failures were occuring within the October depth hoar layer. Sunday temperatures were colder and westerly winds strengthened enough to start moving the recent low density snow to lee N-E aspects. Avalanche mitigation at Copper Mountain caused newly loaded snow to pop out easily with ski cuts, but did not run very far. Avalanche conditions will be a bit tricky over the next couple of days. Where snowfall was not on the ground prior to last week, generally on W-SW-S aspects, signs of instability have been minimal. On other aspects (NW-NE-SE), we have received many reports of collapsing, cracking, and recent slide activity. Several slides have stepped down through the faceted base layer to the ground. These slides have occurred on slopes with two common snowpack features - wind affected and a weak, faceted base layer that formed from older snow. Wind transported snow onto lee NE-E-SE aspects which will add more stress to any weak layers now buried in the snowpack. All signs continue to point toward a conservative approach. Some of the cracks/fractures have propagated long distances showing that the snowpack is storing more energy. You will most likely encounter signs of instability on NW-N-NE-E-SE aspects, where human triggered avalanches remain probable to likely. Avalanche Danger The avalanche danger for the Vail-Summit zone CONSIDERABLE on NW-N-NE-E-SE aspects at all elevations with pockets of HIGH above treeline. On other aspects the danger remains MODERATE. Human triggered avalanches remain probable to likely on steep slopes that contain a weak base layer and are heavily wind loaded.