A Pacific trough off of the West Coast will be broadening and moving east across the Mountain West over the next few days. The jet stream is splitting around Colorado, bringing with it some intense alpine winds that are blowing 25-35 mph this morning and gusting beyond 60 mph. A cold front will stall near the Colorado/Wyoming border today, but we should see an uptick in snowfall tomorrow morning as it drifts south into the Elk Mountains.
Location: Crested Butte Area Date of Observation: 02/21/2017 Name: Zach Guy and Ian Hoyer
Subject: Skier caught and carried in a wind slab Aspect: North East, East, South East, South Elevation: 9000-12000 ft
Avalanches: Observed an unintentional skier triggered wind slab on an E/NE aspect at 12,000 ft, above treeline. The slide broke a few feet above the skier and carried them about 700 vertical feet, resulting in a partial burial, several leg injuries, and a lost ski. The slab ranged from ~5 – 15″ thick, and broke on the 2/17 near surface facet layer. The slide was about 250 feet wide. HS-ASu-R1-D2-I Weather: Broken skies in the a.m., decreased to thin scattered mid-day, increased to overcast in the p.m. Moderate WSW winds, no transport except some plumes on high peaks. Warm temps, green-housing. No precip. Snowpack: On S/SE aspects N/BTL. The recent snow (1″-2″) is wetting and conforming to underlying crust layer. No signs of instability.
On a wind protected NE aspect NTL. A profile showed the 2/17 near surface facet layer (.5- 1mm) buried 8 cm deep. The 1/19 surface hoar layer was 85 cm deep, intertwined with rounded grains. Broken fracture on this layer with very hard additional loading steps. No signs of instability until we got to low elevation, northerly aspects, where we got some rollerballs in the moistening surface snow.
Near and above treeline, there were signs of wind drifting from both NW and SW loading patterns.
Crown ranged from 5-15″ in depth. The avalanche broke on recently buried near surface facets
The slope was a recently wind-loaded NE aspect above treeline in Coon Basin
The skier was partially buried in debris after being carried about 700 vertical feet.
Looking across the crown, which thinned down to ~5″. Slide broke around 250 ft wide.
Profile in Climax Chutes showed unreactive surface hoar layer 3 feet deep, and a fragile layer of facets near the surface.
Location: Kebler Pass Area Date of Observation: 02/21/2017 Name: JD
Subject: Skier Triggered Windslab Aspect: North East Elevation: 12,500
Avalanches: Skier trigger windslab in 40+ degree couloir above tree line. 8″-12″ deep, 15′ feet wide. Cleaned out the middle of the couloir but left small slabs (hangfire) on the sides intact. Just exciting enough for the skier that triggered it. Weather: Partly Sunny, broken, before noon, Overcast in the pm Snowpack:
A Pacific trough is moving onshore along the west coast today. Satellite imagery shows bands of clouds moving across the west under warm, southwest flow. We’ll see a mix of sun and clouds this morning with a general increasing trend into tonight. We may see a few light snow showers in the next 36 hours, but the real accumulations won’t start until Thursday morning. Winds will increase ahead of this system. We look to be on the southern edge of the late-week storm track, but it is looking like 4-8″ could accumulate by the weekend. Stay tuned for changes, and a potentially stronger system early next week.
Today
High Temperature: 32 Wind Speed: 10-20 Wind Direction: SW, W Sky Cover: Increasing clouds Snow: 0
Location: Crested Butte Area Date of Observation: 02/21/2017 Name: Donny
Subject: Mt. Emmons Aspect: North, South Elevation: 9,200-12,200
Avalanches: No signs of instabilities were observed. Weather: Partly cloudy throughout the day, no new snow, periods of strong radiation. Light to moderate NW winds at ridge top. Snowpack: Sun-effected snow was settling quickly. HN24 ranged from 2” below 10,000’ to about 10” in the alpine. Ski Pen ranged from 1” to 12”. New snow seemed to bond to the old snow well and the old facets were still present. It wasn’t dust-on-crust as I expected. Snow on shady aspects was deep and soft – up to 12” and fist hard.
Location: Crested Butte Area Date of Observation: 02/20/2017 Name: Evan Ross, Chris Martin
Subject: Windslabs Aspect: North East Elevation: 9,600ft-10,800ft
Avalanches: Small windslab NE aspect Schuylkill Ridge. Small windslab E aspect above Purple Palace. Large windslab E aspect Purple Mountain.
BTL wide propagating slab N aspect Mount Emmons. Weather: Partly cloudy. Calm winds. Snowpack: At ridgeline windslabs were about 20cm’s deep over SH and well developed NSF. These slabs were confined to right at the rigeline and small in size. Below ridgeline the slab thinned until it was the last 24 hours of new snow at about 6-8cm. Digging around at 10,200ft and lower, the new snow was only over well developed NSF without the SH. The new snow below 10,200 was becoming heavy from warm temps and sun.
Small windslab NE aspect Schuylkill Ridge
IMG_2927
Small windslab E aspect above Purple Palace. Large windslab E aspect Purple Mountain.
Location: Crested Butte Area Date of Observation: 02/20/2017 Name: Zach Guy
Subject: Touchy, small wind slabs Aspect: North, North East, East, South East, North West Elevation: 9,000 – 12,500 ft
Avalanches: Skier triggered 5 or 6 shallow wind slabs, breaking on buried near surface facets, 6-18″ deep. All D1 in size. There were a couple of natural D1 wind slabs as well. These were all above treeline on leeward or crossloaded features. See photos. Weather: Scattered skies. Light to moderate westerly winds, with short periods of light snow transport at ridgeline. Mild temps. Snowpack: About 3″ of new snow, drifts from 6 – 18″ thick below ridgelines and in crossloaded features, mostly above treeline but a few near treeline slopes as well. The new snow is over .5 to 1mm reactive near surface facets, found at all elevations on northerly aspects, and on thick, meltfreeze crusts on southerly aspects. On east aspects N/ATL, the storm interface was a thin, collapsible crust with facets below or just facets. There was not enough new snow for storm instabilities except where it was thickened from wind drifting. We primarily traveled on northerly aspects and found shallow wind drifts to be poorly bonded on the 2/17 near surface facet layer.
Collapsible crust on an E aspect NTL, with facets below.
Cracking in a 12″ wind drift over buried near surface facets, NTL.
Location: Kebler Pass Area Date of Observation: 02/20/2017 Name: Irwin Guides
Subject: 20″ wind slab at Irwin Aspect: East Elevation: 11800 ft
Avalanches: 1 decent windslab triggered in Bender (East, 11,800′, 38 degrees) under foot. SS-ASc-R1-D1.5-I Triggered while walking across the edge of the ridge. 50cm deep, 50′ wide ran 400′ on the February 19 smooth crust. Several small dry loose and wet loose. Weather: Snowpack: 10″ with .9 SWE.
Location: Kebler Pass Area Date of Observation: 02/20/2017 Name:
Subject: Wind Slab Avalanche Aspect: North Elevation: 11,800
Avalanches: SS-ASr-R2-D2-I. A Group of four skiers to our left, remotely triggered a slide from about ~100′ away. Slide was triggered from ridge top. Slide propagated within a large wind roll, proceeded to run ~1,500′. Weather: Sunny, light winds out of the west. Snowpack: No obvious signs of instabilities on the hike up. Noticed some point releases that had run yesterday, all start zones were from under cliff bands.
The slide was triggered from where the 2 skiers are standing in this photo.
Location: Cement Creek Area Date of Observation: 02/20/2017 Name: ADB
Subject: Blue Bird Aspect: North, North East, East Elevation: BTL
Avalanches: Nada. Weather: Few clouds within the area and calm. Snowpack: Between 2 to 5 inches of snow/24 hours. Lower 900 feet had 2 inches on top of rain crust from Friday.
T
