Aspen ===== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, control work, crusts, depth hoar, facets, human triggered avalanches, orographic, precipitation , slabs, surface hoar, trough, weak layers, whumpfing, wind loaded, wind slabs, Mountain Weather and Avalanche Forecast for the Aspen Zone Forecast Issued on 12/6/2007 6:33:44 AM Forecaster: Brian McCall Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Thursday Night Friday Temperature(°F) 21-26 10-15 18-23 Wind Speed(mph) 12-22 4-14 7-17 Wind Direction W SW SW Sky Cover Overcast Overcast Overcast Snow(in) 2-4 8-10 8-10 Snowpack Discussion Light snow showers overnight have brought around 0.5 to 1 inch of new snow to the area. Look for snow totals, as well as avalanche danger, to increase throughout the next few days. The snowpack in the Aspen Zone has been slow to adjust to the weight of last weekend's big storm. Observers in the backcountry are still reporting plenty of whumpfing and some localized cracking, both good signs of unstable snow. Avalanche activity is still occurring, most recently on slopes facing Northeast and East, both above and below treeline as a result of control work at local ski areas. A bigger storm in the forecast for the next four to five days will add yet another load to this already tender snowpack. This new storm snow will be falling on a snow surface made up of surface hoar, surface facets, wind slabs, and crusts. Avalanches may fail initially at this upper snowpack interface, but do the potential to step down to deeper weak layers. On slopes facing NW, N, NE, and E, a layer of weak facets and depth hoar can be found at the base of the snowpack. Avalanches that do step down to this layer could become large and destructive. Extra caution will be required if you are travel on these aspects, especially near and above treeline. Wind slabs that formed during the last storm may give you the false impression of a stronger snowpack under the new snow. Make sure that your digging includes a look for those weak layers below. You will need to constantly assess for changing conditions and make travel decisions and terrain choices accordingly. Avalanche Danger The avalanche danger in the Aspen Zone is CONSIDERABLE on NW-N-NE-E aspects near and above treeline. Human triggered avalanches remain probable on steep wind loaded slopes. On other aspects and below treeline the danger is MODERATE. As new snow accumulates, constantly reassess for rising avalanche danger. Your backcountry observations are very important to us. Observations can be submitted to [59]caic@qwest.net . Front Range =========== Current Keywords: CONSIDERABLE, HIGH, avalanche danger, avalanche paths, explosive, human triggered avalanches, naturally, orographic, paths, precipitation , trough, Mountain Weather and Avalanche Forecast for the Front Range Zone Avalanche Watch in Effect through 12/7/2007 7:00:00 AM Forecast Issued on 12/6/2007 4:28:18 PM Forecaster: Ethan Greene Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Night Friday Friday Night Temperature(°F) 17-22 20-25 15-20 Wind Speed(mph) 10-20G35 10-20G40 10-20G30 Wind Direction W SW SW Sky Cover Overcast Overcast Overcast Snow(in) 4-8 3-6 3-6 Snowpack Discussion There is an Avalanche Watch in effect through 0700 on December 7th for the mountains around I-70 and northward toward Rocky Mountain National Park. Overnight the snow came in fast and furious and then sputtered and sparked all day. Snowfall amounts are still coming into the office, but it looks like 15" in the Loveland and Berthoud Pass areas, over 20" on Berthoud Pass, 14" near Guanella Pass, 10" near Eldora and at least 6" at Cameron Pass. The winds were in the 10-20 mph range with gusts in the 40's. Explosive work near the Eisenhower Tunnel released seven avalanches 2-4' deep, 30-150' wide on northwest and north facing slopes that are above treeline. There were several avalanches in the Berthoud and Loveland Pass corridor that broke into old snow layers. Paths where explosive work has been done earlier in the season released at the new/old snow interface, but untouched paths released near the ground. There was a bank slide along US40 that released naturally with a fracture nearly a half mile long. Our tender snowpack is having a hard time adjusting to the new load. Snowfall will continue overnight and through Friday. Natural and human triggered avalanches remain likely on NW-N-NE-E aspects, especially in the Berthoud Pass area. The snow from the last storm had sometime to adjust to its new environment and gain strength. This might sound like good news, but it could mean that the avalanches are a little harder to trigger and larger in size than the last cycle. Choose your route very carefully and avoid the runnout areas of large avalanche paths. It will be possible to trigger avalanches remotely, so be aware terrain connected to the slopes you are crossing. Avalanche Danger The avalanche danger for the Front Range zone is HIGH on NW-N-NE-E aspects at all elevations. Human triggered avalanches are likely on steep slopes that contain a weak base layer and are heavily wind loaded. Elsewhere, the avalanche danger is CONSIDERABLE. Grand Mesa ========== Current Keywords: LOW, MODERATE, avalanche danger, crusts, orographic, precipitation , settle, trough, whumpfing, wind slabs, Mountain Weather and Avalanche Forecast for the Grand Mesa Zone Forecast Issued on 12/6/2007 7:17:34 AM Forecaster: Ethan Greene Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Thursday Night Friday Temperature(°F) 28-33 15-20 28-33 Wind Speed(mph) 5-15 5-15 5-15 Wind Direction W SW SW Sky Cover Overcast Overcast Overcast Snow(in) 2-4 6-8 6-8 Snowpack Discussion Recent mild temperatures have helped to settle the recent storm snow. The avalanche danger is low where new snow fell on bare ground. Shady aspects that, however, held patches of old snow are quite weak and the new snow layers on top may be sensitive to the weight of a backcountry traveler. The most likely place to trigger an avalanche is on high elevation steep N-NE-E aspects. New snow in the forecast will add further weight to the snowpack. The snow will be falling on a variety of snow surfaces including sun crusts and hard wind slabs. The new snow will easily slide on these 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. The avalanche danger will be on the rise over the next 36 hours. You will need to constantly assess for changing conditions and make travel decisions accordingly. Avalanche Danger The avalanche danger is MODERATE on steep N-NE-E slopes at the higher elevations, where there are underlying pockets of old snow. The danger is LOW on other aspects. As new snow accumulates, constantly reassess for rising avalanche danger. San Juan North ============== Current Keywords: , CONSIDERABLE, LOW, MODERATE, avalanche cycle, avalanche danger, collapsing, crusts, facets, natural avalanche, orographic, precipitation , settle, shear, slabs, trough, whumpfing, wind slabs, wind-loaded, windloading, Mountain Weather and Avalanche Forecast for the Northern San Juan Mountain Zone Forecast Issued on 12/6/2007 6:28:23 AM Forecaster: Mark Rikkers Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Thursday Night Friday Temperature(°F) 29-34 17-22 26-31 Wind Speed(mph) 10-20 15-25 15-25G35 Wind Direction WSW SW SW Sky Cover Overcast Overcast Overcast Snow(in) 3-6 8-10 8-10 Snowpack Discussion Recent mild weather is helping to quickly settle the weekend snow. Observers continue to report a strengthening snowpack, but collapsing and moderate shear results in test pits are still being reported as well. Telluride snow safety got more significant results on Wednesday on N and NW aspects above treeline. The largest concern remains on NW-N-NE aspects, particularly near and above treeline, where cohesionless facets underlie firm, cohesive slabs. Some of these slabs are quite deep due to windloading during the previous storm (fractures as deep as 5' have been reported). Aside from loose activity coming out of steep, sunny aspects with rock or tree outcroppings, our natural avalanche cycle is effectively over. New snow in the forecast will add further weight to the snowpack and develop fresh slabs. The snow will be falling on a variety of snow surfaces including sun crusts, hard wind slabs and near-surface facets. These will not make the best bonding surfaces with the new snow, but temperatures during the early part of the storm will play a role in determining that as well. This storm is moving in warm and our snow surfaces are relatively warm - this combination will help new snow to bond initially. However, with the total amount of snow we are anticipating through the next few days, combined with SW winds transporting snow onto northerly aspects, we will be seeing another round of avalanche activity before the storm clears. On shady aspects where the weak base layers exist, 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. The avalanche danger will be on the rise Thursday. You will need to constantly assess for changing conditions and make travel decisions accordingly. Avalanche Danger The avalanche danger is CONSIDERABLE on NW-N-NE aspects at all elevations. On E and W aspects, the danger is MODERATE near and above treeline and LOW below treeline. On SE-S-SW aspects, the danger is MODERATE above treeline and LOW near and below treeline. Unstable slabs are still probable on steep, wind-loaded northerly terrain and the danger will rise as this storm progresses - check our afternoon update to keep up-to-date! San Juan South ============== Current Keywords: MODERATE, avalanche danger, crusts, facets, orographic, path, precipitation , settle, surface hoar, trough, whumpfing, wind loaded, wind slabs, Mountain Weather and Avalanche Forecast for the Southern San Juan Mountain Zone Forecast Issued on 12/6/2007 7:25:56 AM Forecaster: Ethan Greene Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Thursday Night Friday Temperature(°F) 31-36 17-22 35-40 Wind Speed(mph) 9-19 6-16 5-15 Wind Direction SW SW SW Sky Cover Increasing Overcast Overcast Snow(in) 3-6 10-12 10-12 Snowpack Discussion Recent mild weather has helped to quickly settle the weekend snow. The primary concern remains on N-NE-E aspects where pre-existing old facets have created a weak base layer underneath the recent snowfall. On Monday, a sizeable skier triggered avalanche slid on the N facing Hour Glass path at 11,400'. Significant surface hoar formed during the middle of the week. We are headed into another very stormy period for the Southern San Juan zone. Snow should start during the day and increase in intensity overnight. We expect heavy snow overnight and through a good portion of the weekend. Storm totals could be in the 30-40" range, again. The new snow will fall on a variety of snow surfaces including sun crusts, hard wind slabs, and surface hoar. The damp snow may bond well to some of these surfaces, but if we bury a the surface hoar, expect the worst. Today is a good day to get out early and check the condition of the snow surface. What you see this morning will probably be your problem over the next couple of days. On shady aspects where there is a weak basal layer, slides could step down into the older snow are create large, destructive avalanches. Watch for signs of instability such as cracking, whumpfing, and recent avalanche activity. The avalanche conditions will be changing so be prepared to change your plans accordingly. Avalanche Danger The avalanche danger will rise today to an overall MODERATE. Watch for steep pockets of wind loaded snow with old facets underneath. The avalanche danger will be rising over the next few days as new snow accumulates. Sangre de Christo ================= Current Keywords: avalanche danger, crusts, faceted, human triggered, orographic, precipitation , settle, trough, whumpfing, wind slabs, Mountain Weather and Avalanche Forecast for the Sangre De Cristo Zone Forecast Issued on 12/6/2007 7:28:47 AM Forecaster: Ethan Greene Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Thursday Night Friday Temperature(°F) 25-30 19-24 24-29 Wind Speed(mph) 10-20 15-25 15-25G35 Wind Direction W SW SW Sky Cover Increasing Overcast Overcast Snow(in) 1-4 4-8 4-8 Snowpack Discussion Mild temperatures on Tuesday likely helped to settle the snowpack in many locations. In other zones, we continue to receive reports of human triggered slides in areas where old snow has become a weak faceted base layer underneath recent storm snow and stiff surface wind slabs. You are most likely to find this combination of features on steep N-NE-E aspects near and above treeline. New snow in the forecast will be falling on a variety of snow surfaces including sun crusts and hard wind slabs. The new snow will easily slide on these 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. The avalanche danger will be on the rise Thursday. You will need to constantly assess for changing conditions and make travel decisions accordingly. Avalanche Danger We have insufficient data to rate the avalanche danger in the Sangre de Cristo Zone. As new snow accumulates, constantly reassess for rising avalanche danger. Please send observations from this or any other zone to [59]caic@qwest.net Sawatch ======= Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, crusts, orographic, precipitation , settle, slabs, trough, whumpfing, wind slabs, windloaded, Mountain Weather and Avalanche Forecast for the Sawatch Range Zone Forecast Issued on 12/6/2007 6:47:32 AM Forecaster: Brad Sawtell Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Thursday Night Friday Temperature(°F) 23-28 14-19 21-26 Wind Speed(mph) 17-27G40 15-25G30 15-25G30 Wind Direction W SW SW Sky Cover Overcast Overcast Overcast Snow(in) 4-6 8-10 8-10 Snowpack Discussion Mild temperatures up to yesterday helped settle the snowpack in many locations. Although accross the soze, the snowpack is shallow, deep windloaded pockets can be found on concave shaped slopes and gullies. You are most likely to find this combination of features on steep NW-NE-SE aspects near and above treeline. A foot of new snow in the forecast will add further weight to the snowpack. The snow will be falling on a variety of snow surfaces including sun crusts and hard wind slabs. The new snow will easily slide on these 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 observant for signs of instability such as cracking, whumpfing, and recent avalanche activity. The avalanche danger will be on the rise throughout today. You will need to constantly assess for changing conditions and make travel decisions accordingly. The most likely location to trigger an avalanche could be found on slopes steeper than 30 degrees at and above tree line that face North through East through South East. If you choose to ride, ride one at a time and have an escape route planned. Avalanche Danger The danger in the Sawatch zone is generally MODERATE with areas of CONSIDERABLE danger on N-NE-E-SE aspects near and above treeline. Watch for pockets of unstable slabs on steep, wind-loaded slopes. As new snow accumulates, constantly reassess for rising avalanche danger. Please [59]send us observations if you are getting out. Steamboat ========= Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, explosives, orographic, precipitation , ski cut, trough, wind drift, Mountain Weather and Avalanche Forecast for the Steamboat and Parks Range Zone Forecast Issued on 12/6/2007 4:17:15 PM Forecaster: Ethan Greene Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Night Friday Friday Night Temperature(°F) 13-18 24-29 12-17 Wind Speed(mph) 10-20 10-20 10-20 Wind Direction WSW SSW SW Sky Cover Overcast Overcast Overcast Snow(in) 3-6 3-6 3-6 Snowpack Discussion New snow totals in the Steamboat zone are in the 4-8" range in the last 24 hours. The winds have generally been from the west in the 15 mph range with gusts in the 30's. We haven't been sure until now, but it appears the Steamboat zone is suffering from the same early season snowpack woes as the rest of the northern mountains. Today, avalanche professionals in the zone ski cut several full depth avalanches. The slides were about 3' deep and up to 200' wide. They released on slopes steeper than 38° that face northeast at about 10,600'. Some of the slopes did not release with explosives, then later fractured with ski cuts. These are indications of a tender and tricky snowpack. The most likely place to find these conditions are on slopes that face NW-N-NE-E. The old snow on these slopes is quite weak, and you don't necessarily need to be on a wind drift to release an avalanche. More snow is headed to the Steamboat zone, so watch for an increasing danger over the next few days. Although the snowpack is tender, it is not very deep. If you get caught in a slide there is a good chance of getting trundled through the rocks and bushes. Avalanche Danger The avalanche danger in the Steamboat Zone is CONSIDERABLE on NW-N-NE-E aspects. Elsewhere the avalanche danger is MODERATE. As more snow falls over the next few days, the avalanche danger will rise. Vail ==== Current Keywords: CONSIDERABLE, HIGH, MODERATE, avalanche danger, collapse , faceted, human triggered avalanches, orographic, precipitation , settled, slabs, trough, wind loaded, Mountain Weather and Avalanche Forecast for the Vail and Summit County Zone Forecast Issued on 12/6/2007 6:34:19 AM Forecaster: Brad Sawtell Weather Synopsis The shortwave trough that brought heavy snow to the Front Range mountains is moving off to the east. A very moist westerly flow will continue through the early evening before shifting to the southwest. As the flow shifts, the next jet maximum moves into the state. This combination will produce steady snowfall in many mountain areas. This scenario is different that last weekend, but similar in the fact that the orographic flow is the main lifting mechanism. Thus, areas favored by southwest flow will get the deepest accumulations. Sustained precipitation should continue into Friday and become heavy in the afternoon as impulses a head of a large Pacific trough move into Colorado. This looks like another major event with storm totals in the 2-4' range in portions of the central and southern mountains by Sunday. Keep your fingers crossed! Weather Thursday Night Friday Friday Night Temperature(°F) 25-30 19-24 21-26 Wind Speed(mph) 10-20G30 10-20 10-20 Wind Direction W WSW SW Sky Cover Overcast Overcast Overcast Snow(in) 3-6 6-8 4-6 Snowpack Discussion The snowpack accross the zone has settled some the past few days with the warmer temperatures, but is still shallow and weak. In general, soft and hard slabs are sitting above weak faceted grains. The winds have transported snow making loaded areas the common location to trigger an avalanche. Several avalanches have been both spoted and triggered, at and above tree line on North through East aspects. None of which were very large but big enough to ruin your day. Today through the weekend, expect the stability to decrease as more snow and blowing snow will stree the existing strength to the edge. Yesterday near Quandary Peak I found a very weak snowpack where stability tests would collapse on excavation. Overnight snow totals around the zone range from 4 to 9 inches with the most intense snowfall to arrive before this afternoon. If you do venture out in the backcountry today, expect a tender snowpack and it will be probable to likely that you will trigger a slide. Meaning the avalanche danger will most likely rise by this afternoon. Ride slopes one at a time and avoid any slope steeper than 30 degrees, especially ones that are at and above tree line that face North East through South East. As we move into the afternoon expect to find pockets of HIGH danger on steep wind loaded slopes and gullies on NE-E-SE aspects at and above tree line. Soft slabs will be forming continually today. Continually re-evaluate slopes and consider avoidance all together. Avalanche Danger The avalanche danger for the Vail-Summit zone is CONSIDERABLE on NW-N-NE-E-SE aspects at all elevations. Human triggered avalanches remain probable on steep slopes that contain a weak base layer and are heavily wind loaded. Elsewhere, the avalanche danger is MODERATE. Expect the danger to rise throughout the day especially on NE-SE aspects. As new snow accumulates, constantly reassess for rising avalanche danger.