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November 19th – Sunny

CB Avalanche Center November 20, 2014Weather

24 Hour Weather Outlook

Weather Discussion: Nunc ac ipsum vel nulla dignissim auctor. Nulla gravida fermentum tempus. Phasellus ut mollis lorem, a auctor mi. In rutrum turpis sit amet feugiat tincidunt. Fusce sollicitudin mi tellus, non tincidunt nulla sodales in. Nam eu suscipit enim. Nullam eu massa ultrices, lobortis orci vel, scelerisque metus.
Temperature:10˚
Wind Speed (mph):10 – 20 mph
Wind Direction:S
Sky Cover:Clear
Snow (in):0″

48 Hour Weather Outlook

Weather Outlook: Nunc ac ipsum vel nulla dignissim auctor. Nulla gravida fermentum tempus. Phasellus ut mollis lorem, a auctor mi. In rutrum turpis sit amet feugiat tincidunt. Fusce sollicitudin mi tellus, non tincidunt nulla sodales in. Nam eu suscipit enim. Nullam eu massa ultrices, lobortis orci vel, scelerisque metus.
Tomorrows Temperatures:10-15
Tomorrows Wind Speeds (mph):10-20 mph
Tomorrows Wind Directions:SW
Tomorrows Sky Cover:Mostly Clear,Few Clouds
Tomorrows Snow (in):0″

Todays Forecast

CB Avalanche Center November 20, 2014Weather

Weather Discussion: Nunc ac ipsum vel nulla dignissim auctor. Nulla gravida fermentum tempus. Phasellus ut mollis lorem, a auctor mi. In rutrum turpis sit amet feugiat tincidunt. Fusce sollicitudin mi tellus, non tincidunt nulla sodales in. Nam eu suscipit enim. Nullam eu massa ultrices, lobortis orci vel, scelerisque metus.
Temperature:10˚
Wind Speed (mph):10-20 mph
Wind Direction:N
Sky Cover:Clear
Snow (in):0″

Mount Owen Jenga Chute Avalanche

CB Avalanche Center November 7, 20142014-15 Observations, Avi-map

The CBAC got up to Mount Owen today to investigate yesterday’s slide that caught and carried two skiers as they boot packed up Jenga Chute. The slide broke above the pair near the top of the couloir as they were about halfway up the chute. The area received 10-12″ of snow on the night of November 2nd which fell on a variety of surfaces ranging from bare ground to up to 2ft residual of snow from the few storms that rolled through the Elk Mountains in October.

The avalanche should be classified SS-AF-R2-D1.5-O/G. The slope angle ranged from 37-41º on an ENE facing slope (61º). It ran ~400 vertical feet from ~12,600ft to 12,200ft. Debris width spread about 60ft wide, ranging in depth from 40-150cm deep.

The snow structure of the slab in the couloir consisted of two distinct graupel layers that fell in our most recent storm, capped by a thin windslab generally 3-6″ deep created by light winds during and after the storm; however, the new snow has drifted into 1-2ft deep isolated pockets. The slab failed and ran on a 4cm “pencil+” hard melt freeze crust from the October 12th storm, although it did scour down to rock within parts of slide path. Up to 50cm of 1-2mm faceted grains remained below the bed surface, which will continue to mature/grow in size as the season progresses, likely causing more concerning instabilities in the months to come, in this location and surrounding slopes.

The CBAC would like to genuinely and humbly thank those involved for sharing their experience for the greater awareness of our Crested Butte backcountry community as we plunge into another winter.

Get ready for winter!!

CB Avalanche Center September 18, 2014Avi-Off-Season

The gold leaves and some snow in next week’s forecast are both good reminders that winter is just around the corner! Before the flakes start piling up, fall is a great time to freshen up on your avalanche education, or set aside some money and time to take an avalanche course. I’ve put together a list of a few educational opportunities below.

Avalanche Training/Lectures

WMRT Avalanche Seminar. 7 pm, November 20th, 2014. Western State Colorado University

CBAC Avalanche Awareness Night. December 6th, 2014. CB Center for the Arts
A night of avalanche talks, beer drinking, silent auction, raffle, and winter stoke, all to support your local avalanche center

CBAC Beacon Brushup. December 7th, 2014. CB Town Park.
Learn how to conduct an avalanche search or tune-up your beacon skills.

AIARE Avalanche Courses
Level 1, Level 2, and refresher courses offered locally through Crested Butte Mountain Guides or check AIARE’s schedule for courses around the country.

Colorado Snow and Avalanche Workshop. October 17th, 2014. Breckenridge, CO
A one-day seminar aimed at avalanche professionals, but with plenty of material for motivated recreationists.

Weather Forecasting Courses

Sick of your local weather experts blowing the forecast?
Mountain Weather Workshop. October 31st – November 2nd, 2014. Silverton, CO
Winter Weather Forecasting. October 10th-12th, 2014. Jackson, WY

Oh no! Dust on snow

CB Avalanche Center March 31, 2014Avi-Off-Season

Yesterday, we got a brief and silty taste of the Dirty Thirties when a major dust storm blew over Crested Butte. Scarp Ridge recorded wind speeds of 110 mph (the highest of the season), and these winds brought with them a sizeable chunk of Moab.

Dust-ageddon in Crested Butte on March 30, 2014. Photo credit: Matt Hogan

How will this dust on snow event affect snow stability and avalanches? Lets start with a key concept: albedo. Albedo is how reflective a surface is. White colors have a high albedo — they reflect a high amount of radiation energy rather than absorb it. That is why you reach for a light colored T-shirt if you’re going outside on a hot sunny day instead of a black T-shirt. Fresh snow has a very high albedo and it reflects most incoming solar energy. (So thats why my mom always made me double up on sunscreen when I went skiing!) On the other hand, the dark-colored dust more readily absorbs solar energy and heat, and also retains that heat longer.

Pristine snow reflects radiation more effectively than dusty snow. Courtesy of Jeff Deems.

Dusty snow can absorb two or three times the solar energy of a clean snowpack. Whenever dust is near the surface of the snow (even when its buried up to a foot deep), it amplifies the rate of surface warming, increasing the amount of snowmelt and weakening the snow around it. This leads to more frequent loose wet avalanches. Intense melt rates send freewater deeper into the snowpack, which can also compromise the strength of deeply buried weak layers, causing an increased likelihood of wet slab avalanches. Both of these problems, with or without dust, can be avoided by monitoring how well the snowpack refreezes at night and getting off of slopes before they thaw too much. Dust on the snow simply shortens that window of stable snow and may prevent good overnight refreezes in some situations.

Snirt. Snow+Dirt. Photo taken March 31, 2014 near Crested Butte.

The second avalanche concern is that dust can do weird things when its buried by a slab of snow, and it can behave like a persistent weak layer. Because they absorb and retain heat longer, dust layers can cause wet grains above or below them to remain unfrozen and unstable longer. Dust can also cause tremendous temperature gradients in the surrounding layers, which causes the bordering snow around it to decay and facet. This is not always the case, but it is worth checking on how reactive dust layers are after they get buried by spring storms. It will be the easiest layer you will ever identify in a snowpit!

The crown of a large slab avalanche that was remotely triggered from hundreds of yards away last spring. It failed on a dust layer.

Sadly, dust on snow has negative impacts on the timing of spring runoff and water resources in the West. The Center for Snow and Avalanche Studies in Silverton, CO tracks and studies the effects of dust-on-snow events, and is a great resource for more information on this topic. On the bright side of things, your favorite mountain bike trails will melt out sooner now, and business is booming if you own a car-wash business.

Zach Guy
CBAC Forecaster

A Canary in the Elk Mountains?

CB Avalanche Center March 19, 2014Avi-Off-Season

Canaries were once used in coal mining as an early warning system for toxic gases leaking into the mine. Signs of distress, or worse, a dead bird, would caution the miners that it was time to retreat from the mine.

Last week, a warm airmass brought our first real taste of spring to the Elk Mountains. Nothing out of the ordinary as far as Crested Butte weather goes, but enough that pale white skin made its spring debut on Elk Street before hastily retreating to aloe vera treatments. On Sunday and Monday (March 9 and 10), temperatures rose to just above freezing at 12,000 feet under an intense March sun. Days later, following a few inches of snow and cooler temperatures, we observed the results of some very unnerving deep slab avalanches. Sometime after Monday evening, a huge slab tore off of the south face of Mt. Owen. This appeared to be triggered by a cornice falling onto a shallow part of the slope, but it propagated to parts of the slab that were 12 feet deep.

Deep slab on Mt. Owen, first spotted 3/12/14

Looking down the crown

On Wednesday night, another monster ripped off of a southwest facing ridge near Avery Peak. This one raised the hairs on the back of my neck. Two deep slabs back to back, under relatively mild and stagnant weather. The Avery slide did not appear to be cornice-fall triggered, and has raised a lot of questions and spurred a lot of speculation on the failure mechanics among local and statewide avalanche professionals. Although meltwater on high elevation terrain has been pretty minimal to this point, it seems plausible that a hot spot on the slope, such as a sunbaked rock or simply an oven-like part of the slope, could have channeled heat and meltwater into a shallow part of the snowpack. Once meltwater percolates to a buried weak layer, it can compromise the layer’s strength causing a wide and destructive failure. The timing of these events can be unpredictable. Maybe warming had subtle effects on the slab properties that added up just enough on this slope. We’re still not sure.

And another. This one near Avery Peak.

With just a tease of spring under our belt and much more warm and sunny weather inevitably to come, this begs the question: Are we seeing the tip of the iceberg right now? Did the canary just faceplant into the bottom of the cage? Warming and meltwater will continue progressing into the snowpack, first on southerly slopes, and eventually around the compass to north. We know weak layers are at the bottom of the snowpack lurking and they are proving to be reactive. Cornice falls will become more frequent as these overhanging blocks of snow continue to thaw and sag from their own massive amounts of weight. We are not out of the woods yet when it comes to deep slab problems. These last two slides should serve as a healthy reminder to use an extra dose of caution this spring in your backcountry travels. Be diligent in your terrain selection and in the attention you give to weather, snowpack, and avalanche patterns in the upcoming months.

Zach Guy
CBAC Forecaster

Huge Deep Slab off of Mt. Owen

CB Avalanche Center March 16, 2014Videos

Recapping a historic avalanche cycle

CB Avalanche Center February 21, 2014Avi-Off-Season

Zach Guy
CBAC Forecaster

The first two weeks of February were exciting (but sleepless) times to be an avalanche forecaster. An unusually large storm was accompanied by unusual avalanches. Around the central and northern mountains of Colorado, avalanches destroyed or buried buildings, closed roads, and extended trim lines of previous historic paths. Sadly, four fatalities occurred as well.

I put together a simplified summary of the storm and a timeline of natural avalanche activity, highlighting some of the largest and/or most unusual avalanches that occurred around our Crested Butte backcountry and surrounding roads. I’m certain this is only a small percentage of the natural avalanches; our zone is too vast to get the full picture from our lookout points and observations. I ordered and dated these avalanches according to the first date that they were observed or reported to us, but the exact failure dates are open for speculation.

The storm began January 30^th, with a quick and massive hit of roughly 4.0” of SWE in the favored zones and 2.0” of SWE near town in just 60 hours. Natural avalanches were widespread, but confined to the new snow, and most common at low elevations where the surface snow was weakest. We were a bit surprised not to see any deeper slides in the alpine when the clouds cleared for a day on February 2^nd. Maybe our snowpack was tougher than we thought??

Anthracite Range. Observed February 2nd.

Snowfall picked up again on February 3^rd: fluffy snow, modest accumulations, with moderate winds, and a lull in avalanche activity. On the night of February 7^th, the Pacific river of moisture found a direct path to Crested Butte. Wind assisted snow transport had been steady and relentless for several days, and Gothic was the first to shed in a big way. The NE face ran full track, crossed the East River, and ran uphill burying (and perhaps destroying?) a newly installed outhouse structure in the Judd Falls parking area. Oh crap! Several observers called this one a D4, about as big as they get in Colorado.

Gothic Mountain runout. The pipe is to the top of the outhouse structure that was buried 10-20 feet deep. Observed February 8th.

The river of moisture was relentless until February 10^th, and the favored mountains picked up another whopping 3.5” of SWE while Mt. CB got 2.5” over the 4-day period. Schofield Pass hit 9.5″ of SWE over the storm period. Winds continued at moderate speeds, with the usual stronger gusts. We had no visibility and limited avalanche observations during this time. Then the clouds lifted on February 10th and 11th, and revealed a warzone. Almost everything steep near town had slid, from small road cuts, to river banks, to more sizeable paths. Almost all of Snodgrass had slid, breaking trees and covering Gothic Road in feet upon feet of debris. Debris ran across Peanut Lake Road and onto the nordic tracks. Unusual crowns were all over the mountains closer to CB South. Deep slabs pulled out of the Ruby Range. Slides that hadn’t run in 20 years crossed Cement Creek Road. At least 5 paths crossed Taylor Canyon Road, and several structures near Almont and in Taylor Canyon were impacted. At least 4 paths crossed Spring Creek Road (not sure on the timing of these last few slides…could have been a few days later).

This slide crossed Peanut Lake Road around 8:30 a.m. February 10th.

An estimated 2/3 of Snodgrass Mountain slid to near the ground. Observed February 10th.

Unusual crowns on Double Top Mountain. Observed February 10th

Large slides above town from Gibson Ridge. Observed February 10th.

Crown lines running across the entire width of Cement Mountain. Observed February 10th.

Slides near Meridian Lake. Observed February 11th.

Peeler Basin. Estimated half mile wide. Observed Februay 11th.

Deep slab on Purple Mountain, estimated up to 20+ ft deep. Observed February 11th.

Deep slab on Afley. Observed February 11th.

Small doses of snow fell and wind speeds increased on February 12th through the 15th. Temperatures started to climb, eventually hitting the high 40’s in Crested Butte. We even saw short bouts of rain at all elevations. The natural cycle was far from over. Another natural came down to Cement Creek Road. A few more huge ones ripped off of the peaks.

Near White Mountain; this path ran similar to the notorious skier triggered slide from 2008. Observed February 14th.

Several historic slides crossed Spring Creek Road. Observed February 14th.

Slides across Cement Creek. Observed February 14th and 15th.

Slides impacted structures in Taylor Canyon and near Almont. Observed February 15th.

Slab failing near the ground on Whetstone. Observed February 16th.

Another D4 off of Peeler Mountain. Observed February 17th.

Near WSC Peak. Observed February 17th

This memorable cycle was spooky, challenging, exciting, and stressful all at once. I wish I had a helicopter to fly around the range now to get a full view of the impacts of this cycle.

Thank you to everyone for submitting observations the past few weeks. A special thanks to Ben Pritchett, Ian Havlick, Pete Sowar, Briant Wiles, Andrew Breibart, Jayson Simons-Jones, and Gary Dotzler for their photos.

Digging out the details of this storm. How big was it?

CB Avalanche Center February 13, 2014Avi-Off-Season

Zach Guy

CBAC Forecaster

Natural deep slab off of Afley Peak

Since January 29th, the mountains around Crested Butte have been walloped by heavy snowfall. On February 10th, the storm finally cleared. My back is nearly broken from endless shoveling, my roof has avalanched at least twice, and I’ve heard lots of folks saying this is the biggest storm they’ve ever seen. How historic was this storm?

The Schofield Pass SNOTEL site is a remote weather station north of Gothic Townsite that measures snow depth and snow water equivalent at hourly intervals. Snow water equivalent (SWE) is the amount of water that would melt out of the snow falling from the sky. An inch of rain measures as an inch of SWE, and a foot of snow typically produces about an inch of SWE. Between January 29th and February 10th, Schofield Pass received 9.5” of SWE. That’s easily 10 feet of snow! Since Schofield’s weather station was installed in 1985, four major storms stand out, with a return interval of roughly 6 years: February 1986 (13.5” SWE), February 1995 (9.7” SWE), January 2005 (8.0” SWE), and December 2010 (9.4” SWE). All of these storms came in unusually warm, with abundant moisture streaming from the Pacific. Three out of four of these storms resulted in Extreme avalanche danger, with widespread and long-running avalanches into valley bottoms.

This storm, with 9.5” SWE, is comparable in precipitation levels to these previous historic storms, but it fell over nearly twice the time span. At the avalanche center, we compared our current storm to previous storm patterns to help decide whether to upgrade the danger to extreme. Extreme danger means very large and destructive avalanches are widespread; the type of danger where we might expect Red Lady Bowl to come across Kebler Pass Road. It’s a very challenging forecast when the mountains are socked in clouds and we have very few observations to work off of. During this storm, we rated the avalanche danger as high during 5 days of the storm. After the clouds cleared, we observed widespread avalanches and a dozen or more very destructive avalanches. One ran off of Gothic Mountain, crossed the East River, and buried a structure 20 feet deep! Did we hit extreme danger? I’m not sure..we were dang close. There are two reasons we didn’t bump the danger to extreme on February 10th: The storm reached its maximum precipitation rate early in the storm rather than late, and it happened over a span of 13 days, while the other historic storms came in over 6 or 7 day periods. All in all, it was a memorable storm and ranks as one of the larger storms we’ve seen in the past 30 years. Whether it was at the ski resort, in the backcountry, or driving your car to work, I hope you found some of that fluffy white stuff flying in your face!

Thanks to Art Mears and Ben Pritchett for their contributions to this article.