Aspen ===== Current Keywords: HIGH, avalanche danger, cold front, crusts, drifting, facets, front, naturally, orographic, runout, slab, slabs, surface hoar, trough, weak layers, windslabs, Mountain Weather and Avalanche Forecast for the Aspen Zone Avalanche Watch in Effect through 1/28/2008 10:00:00 AM Forecast Issued on 1/27/2008 4:05:22 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 12-17 15-20 0-5 Wind Speed(mph) 20-30 G60 25-35 G70 20-30 G60 Wind Direction WSW WSW W Sky Cover Overcast Overcast Overcast Snow(in) 9-12 12-16 4-7 Snowpack Discussion The foot or more of snow forecast to fall overnight will add a rapid load to the snowpack. With the strong south and southwest winds, there will be lots of transport, drifting, and slab formation. Can you say avalanches? There are several weak layers in the upper third of the snowpack. There is a mix of slick crusts, feathery surface hoar, and small, loose near surface facets buried under some recent windslabs. The slabs are common near and above treeline on north through east to southeast aspects. A few of the windslabs avalanched naturally over the last few days. The new snow will be sufficient to overload many of these weak layers. Then there are the weak layers near the ground. They are still down there, buried under a sizable load. Getting an avalanche to run full depth is still possible, especially if an avalanche in the upper layers steps down. There is an avalanche watch in effect Sunday night. If the forecast verifies, the watch will be upgraded to a Warning. That means that the danger is HIGH on all aspects. Backcountry travel is will require very good avalanche skills to stay safe, and very careful route selection to avoid all avalanche terrain. Stay on low angle terrain and avoid avalanche runout areas. Avalanche Danger The avalanche danger in the Aspen Zone is HIGH on all slopes. [57]Please let us know if you see any avalanche activity or experienced signs of instability. Front Range =========== Current Keywords: CONSIDERABLE, avalanche danger, cold front, drifting, drifts, front, natural, orographic, slab, slabs, trough, windslabs, Mountain Weather and Avalanche Forecast for the Front Range Zone Forecast Issued on 1/27/2008 4:12:54 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 15-20 15-20 -5 to 0 Wind Speed(mph) 25-35 G60 25-35 G70 20-30 G60 Wind Direction WSW WSW W Sky Cover Overcast Overcast Overcast Snow(in) 3-6 5-8 3-6 Snowpack Discussion Avalanche activity has slowed down, but the few recent avalanches are noteworthy. On Saturday afternoon, a skier triggered a deep slab in Second Creek, north of Berthoud Pass. From his description, it was the classic deep slab instability, triggered from a spot of shallower snow before it propagated into drifts and broke TWELVE feet deep. Fortunately, the slope was short and the slide only ran 150 feet. Tuesday, observers in the Berthoud Pass area reported a natural avalanche on a SE aspect above treeline. Normally, you are most interested in avalanches fresher than 48 hours, but this good-sized natural was 3 feet deep and 400 feet wide. The deep slab problem will not go away, and we will be dealing with it for quite a while to come. Near and above treeline, the snowpack is topped with some shallow windslabs. This next storm will add another layer of slabs on top. The new snow is coming in with strong southwest and west winds. That means plenty of drifting and loading near and above treeline. Expect new slabs sitting on older slabs to add up to sensitive stacks 2-4 feet thick. It will be easy to trigger these windslabs on steep slopes. The slabs will get thicker and more sensitive throughout the day as more snow accumulates. You will need to be very aware of the changing conditions and deteriorating stability. Avalanche Danger The avalanche danger is CONSIDERABLE all aspects and elevations. Human triggered avalanches are probable on all steep slopes. Reactive wind slabs in the upper snowpack and deep slab instabilities are the two concerns. The danger will be rising during the day as more snow accumulates. Grand Mesa ========== Current Keywords: CONSIDERABLE, HIGH, avalanche danger, cold front, drift, front, human triggered avalanches, natural, orographic, slabs, trough, weak layer, windslabs, Mountain Weather and Avalanche Forecast for the Grand Mesa Zone Forecast Issued on 1/27/2008 3:55:01 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 15-20 20-25 2-7 Wind Speed(mph) 10-20 15-25 10-20 Wind Direction SSW SW W Sky Cover Overcast Overcast Overcast Snow(in) 9-12 9-12 3-6 Snowpack Discussion The snowfall forecast for the current storm will increase the avalanche danger. More than a foot of snow is forecast by Monday morning. That is a rapid load, something the snowpack does not like. Snow should continue through Monday with another foot or so accumulating. Add southerly winds at the perfect speed to gently drift the snow, and we will be looking at windslabs two to four feet thick. The snow is coming in relatively warm, which should help it bond to the current snow surface. Unfortunately there is a weak layer buried underneath last Thursday's storm. Expect to see natural and human-triggered avalanches running on that buried weak layer, at the current snow surface, and within the storm snow. Steer well clear of steep slopes, and avoid traveling underneath them. [57]Even as small avalanche can ruin your day. Avalanche Danger For Monday, the avalanche danger is HIGH on north, north, northeast, east, southeast, and south aspects near and above treeline. Natural and human triggered avalanches are likely. The danger is CONSIDERABLE on other aspects and well below treeline. You will find some soft slabs forming in large, north facing openings in the trees. Please send observations from this or any other zone to [58]caic@qwest.net San Juan North ============== Current Keywords: HIGH, avalanche danger, cold front, crust, dense, drifting, facet, facets, front, orographic, run out, settle, slab, trough, weak layers, windslabs, Mountain Weather and Avalanche Forecast for the Northern San Juan Mountain Zone Avalanche Watch in Effect through 1/28/2008 10:00:00 AM Forecast Issued on 1/27/2008 4:02:20 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 15-20 17-25 -5 to 0 Wind Speed(mph) 20-30 G60 20-30 G60 15-25 G50 Wind Direction SSW SW W Sky Cover Overcast Overcast Overcast Snow(in) 10-15 8-11 5-8 Snowpack Discussion The foot or more of snow forecast to fall overnight will add a rapid load to the snowpack. With the strong south and southwest winds, there will be lots of transport, drifting, and slab formation. We will be looking at windslabs many feet thick. Can you say avalanches? The new snow is coming in warm and dense, which will help it bond to the underlying snow. Winds picked up Saturday night and really stiffened the snow surface. Unfortunately, there are plenty of weak layers buried in the upper third of the snowpack on most slopes near and above treeline. Southerly aspects turned into a crust and facet sandwich, and weak near surface facets are trapped under the most recent windslabs. Some of these weak layers had begun to settle out, but the new snow will be sufficient to overload many of them. There is an avalanche watch in effect Sunday night. If the forecast verifies, the watch will be upgraded to a Warning. That means that the danger is HIGH on all aspects. Backcountry travel is will require very good avalanche skills to stay safe, and very careful route selection to avoid all avalanche terrain. Stay on low angle terrain and avoid avalanche run out areas. Avalanche Danger The avalanche danger in the Northern San Juan Zone is HIGH on all slopes. [57]Please let us know if you see any avalanche activity or experienced signs of instability. San Juan South ============== Current Keywords: HIGH, avalanche danger, cold front, dense, density, drifting, facets, front, orographic, runout, slab, surface hoar, trough, weak layers, windslabs, Mountain Weather and Avalanche Forecast for the Southern San Juan Mountain Zone Avalanche Watch in Effect through 1/28/2008 10:00:00 AM Forecast Issued on 1/27/2008 3:59:15 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 15-20 17-22 0-5 Wind Speed(mph) 15-25 G50 20-30 G60 15-25 G50 Wind Direction SSW SW WSW Sky Cover Overcast Overcast Overcast Snow(in) 12-18 10-15 4-7 Snowpack Discussion The foot or more of snow forecast to fall overnight will add a rapid load to the snowpack. With the strong south and southwest winds, there will be lots of transport, drifting, and slab formation. We will be looking at windslabs many feet thick. Can you say avalanches? Even without buried weak layers we would expect activity from a storm this size. The new snow starts warm and dense, which will help it bond to the underlying snow. Unfortunately, the underlying snow is low density, and sitting on top of buried surface hoar and facets. Not much of a foundation for a good-sized storm. There is an avalanche watch in effect Sunday night. If the forecast verifies, the watch will be upgraded to a Warning. That means that the danger is HIGH on all aspects. Backcountry travel is will require very good avalanche skills to stay safe and very careful route selection to avoid all avalanche terrain. Stay on low angle terrain and avoid avalanche runout areas. Avalanche Danger The avalanche danger in the Southern San Juan Zone is HIGH on all slopes. [57]Please let us know if you see any avalanche activity or experienced signs of instability. Sangre de Christo ================= Current Keywords: avalanche danger, cold front, front, orographic, slab, slabs, trough, wind loaded, wind slabs, windslabs, Mountain Weather and Avalanche Forecast for the Sangre De Cristo Zone Forecast Issued on 1/27/2008 3:52:06 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 12-17 20-25 0-5 Wind Speed(mph) 25-35 G70 30-40 G70 30-40 G50 Wind Direction SW SW W Sky Cover Mostly Cloudy Mostly Cloudy Overcast Snow(in) 0-4 1-4 0-3 Snowpack Discussion Our last observation from the Sangres was over two weeks ago and noted plenty of hard slabs to be found. The slabs were primarily on the lee aspects due to persistent northerly winds, but could be found on cross loaded terrain features like gullies as well. The Sangres have a relatively shallow snowpack. The primary concern in neighboring zones with shallow snowpacks is localized deep slab instabilities. The stiff wind slabs will hold your weight in many areas, but you can breakthrough weak spots especially near cliffs, rock outcroppings and vegetation. If you do trigger a slide from a weak spot, it could cause the entire snowpack to slide creating a large avalanche. As you travel, constantly reevaluate the snowpack for signs of these instabilities. Think of the consequences of a big ride during your route selection process. The Sunday-Monday storm will just brush the range, so expect some new windslabs forming on Monday. A few inches of snow and the strong southwesterly winds will load north, northeast, and east aspects near and above treeline. As always, we really like to get observations, even if it is just cloud cover and new snow from the valley floors. Avalanche Danger We have insufficient information to issue an avalanche danger for the Sangre De Christo zone. Carefully evaluate steep wind loaded slopes and be very aware of changing conditions. Please send observations from this or any other zone to [57]caic@qwest.net Sawatch ======= Current Keywords: HIGH, avalanche danger, cold front, dense, drifting, front, naturally, orographic, runout, shears, slab, slabs, trough, weak layers, windslabs, Mountain Weather and Avalanche Forecast for the Sawatch Range Zone Avalanche Watch in Effect through 1/28/2008 10:00:00 AM Forecast Issued on 1/27/2008 3:56:11 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 12-17 15-20 -5 to 0 Wind Speed(mph) 25-35 G60 25-35 G70 20-30 g60 Wind Direction SWWSW W W Sky Cover Overcast Overcast Overcast Snow(in) 5-10 4-8 3-6 Snowpack Discussion The foot of snow forecast to fall overnight will add a rapid load to the snowpack. With the strong south and southwest winds, there will be lots of transport, drifting, and slab formation. Can you say avalanches? The new snow is coming in warm and dense, which will help it bond to the underlying snow. Unfortunately, there are two concerns within the older snow. At the surface are recent, shallow windslabs. A few of the slabs avalanched naturally Friday and Saturday. The new snow will overwhelm many of them, causing more slides. Then there is a deep, and scarier, problem. Stability tests fail moderate to strong on several deep weak layers, but the shears are fast and planar. This can be an indication of "false stable" conditions, where the snowpack appears to be much stronger than it really is. The clean shears indicate the weak layers can propagate a fracture a long distance, meaning you could trigger a big avalanche from the center or bottom of a slab. Big deep slabs are still an important concern. There is an avalanche watch in effect Sunday night. If the forecast verifies, the watch will be upgraded to a Warning. That means that the danger is HIGH on all aspects. Backcountry travel is will require very good avalanche skills to stay safe, and very careful route selection to avoid all avalanche terrain. Stay on low angle terrain and avoid avalanche runout areas. Avalanche Danger The avalanche danger in the Sawatch Zone is HIGH on all slopes. [57]Please let us know if you see any avalanche activity or experienced signs of instability. Steamboat ========= Current Keywords: CONSIDERABLE, HIGH, avalanche cycle, avalanche danger, cold front, drifted, front, natural avalanche, natural avalanches, orographic, runout, slabs, starting zones, stress, trough, Mountain Weather and Avalanche Forecast for the Steamboat and Parks Range Zone Forecast Issued on 1/27/2008 3:50:11 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 12-17 17-22 0-5 Wind Speed(mph) 20-30 15-25 20-30 Wind Direction SW SW W Sky Cover Overcast Overcast Overcast Snow(in) 10-14 9-12 6-10 Snowpack Discussion Reports of natural avalanches started coming in on Saturday. Observers spotted a handful of slides up to 4 feet deep. Winds drifted enough snow to form slabs in the avalanche starting zones. Those slabs are going to be stress to their limit as this next storm rolls in. Expect a natural avalanche cycle near and above treeline sometime during this storm. The snowy January continues. You will need to be very aware of the changing conditions and deteriorating stability as the snow adds up on Monday. Backcountry travel is will require very good avalanche skills to stay safe, and very careful route selection to avoid all avalanche terrain. Stay on low angle terrain and avoid avalanche runout areas. Avalanche Danger The avalanche danger in the Steamboat Zone is HIGH on north, northeast, east, and southeast aspects near and above treeline, especially as more snow accumulates. On other slopes near and above treeline and all slopes below treeline the danger is CONSIDERABLE. If you have any observations or data to share, please send them to [57]caic@qwest.net. Vail ==== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, cold front, crossloaded, crown, drift, drifted, drifting, front, human triggered, human triggered avalanches, lee , natural, orographic, path, shears, slab, slabs, trough, weak layers, wind drifts, windslabs, Mountain Weather and Avalanche Forecast for the Vail and Summit County Zone Forecast Issued on 1/27/2008 4:09:04 PM Forecaster: Spencer Logan Weather Synopsis There is a subtropical airmass poised to slam into southern Colorado Sunday afternoon. The airmass is warm, with lots of available moisture. It comes in on good soutwesterly flow, with strong ridgetop winds to increase the orographic effect, and a jet streak that moves over the Four Corners late Monday night to further enhance the dynamics. The heaviest snowfall will be overnight in the San Juans, around midnight, and a little later in the Elks. Upper level flow becomes more zonal Monday morning. Late Monday afternoon the trough axis and an associated cold front sweep in from the northwest. Expect a sharp drop in temperatures, as much as 20F. The front kicks off another strong period of snowfall. Snowfall tapers off after midnight Monday as a ridge builds. Flow remains northwesterly, and the next storm arrives late Tuesday night. The long-range models stack up several more storms behind. Weather Sunday Night Monday Monday Night Temperature(°F) 15-20 15-20 -5 to 0 Wind Speed(mph) 20-30 G50 20-30 G70 15-25 G50 Wind Direction WSW WSW W Sky Cover Overcast Overcast Overcast Snow(in) 5-8 5-8 3-6 Snowpack Discussion Avalanches from Saturday: There was a shallow skier-triggered avalanche in the East Vail area. The skier was carried over some cliffs but escaped the slide and injury. It was on a northerly aspect at 11,700 feet, about 1 foot deep, 150 feet wide, and ran 300 vertical feet. Saturday afternoon a snowboarder triggered an avalanche in the Little Professor, a crossloaded, southeast facing slide path near Arapahoe Basin. Again, the slide was only about 1 foot deep, 200 feet wide, and ran 300 vertical feet. Both the human triggered slides involved just the recently loaded and drifted snow. On an easterly aspects south of Jacques Peak, a small, shallow natural ran mid-morning. Control work Saturday morning triggered a few shallow slides in crossloaded areas near treeline. Winds have loaded snow onto lee aspects near and above treeline on north through east to southeast aspects. Cross loading has occurred on north westerly and southerly aspects as well. Observers report reactive 1-2 foot thick wind drifts just below ridges. The new snow is coming in with strong winds. That means plenty of drifting and loading near and above treeline. Expect new slabs sitting on older slabs to add up to sensitive stacks 2-4 feet thick. It will be easy to trigger these windslabs on steep slopes. The slabs will get thicker and more sensitive throughout the day as more snow accumulates. You will need to be very aware of the changing conditions and deteriorating stability. Then there is a deeper, and scarier, problem. Stability tests fail moderate to strong on several deep weak layers, but the shears are fast and planar. This can be an indication of "false stable" conditions, where the snowpack appears to be much stronger than it really is. The clean shears indicate the weak layers can propagate a fracture a long distance, meaning you could trigger a big avalanche from the center or bottom of a slab. A skier triggered a slide on Berthoud Pass Saturday, and reported the crown broke through a 12 foot deep drift. Big deep slabs are still an important concern. Avalanche Danger The avalanche danger in the Vail-Summit Zone is CONSIDERABLE on all aspects near and above treeline. Human triggered avalanches are probable on steep slopes. You will need to be very aware of the changing conditions through the day. The avalanche danger is MODERATE on all slopes below treeline.