Mountain Weather 12/31/15

CB Avalanche CenterWeather

Date: 12/31/2015

The arctic airmass remains in place over most of the West. Mountain temperatures are hovering just above zero this morning, and may not crest single digits today. The last in a series of weak shortwaves will generate another inch or few this morning before skies clear and we ring in the New Year with subzero temps. We’ll see a warming and drying trend going into the weekend under weak high pressure.

Irwin Cat ski obs

CB Avalanche Center2015-16 Observations

Location: Kebler Pass Area
Date of Observation: 12/30/2015
Name: Irwin Guides
Subject: Irwin Cat ski obs
Aspect:
Elevation: 10,000-12,000 ft.

Avalanches: Sensitive shallow windslabs 6-8” forming across westerly terrain of UWW, EBM, SBM, considering shallow depth, propagating widely, easily mitigated with any kind of traffic immediately.
Weather: Cold, snowy, blustery day.
Snowpack: appears settlement has flattened out at 46. Boot pen is not to ground anymore, and ski pen ~10-20cm. Light low density snow, 2” last night, 1.5” during day.

Troublesome persistent slab results

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/30/2015
Name: Zach Guy
Subject: Troublesome persistent slab results
Aspect: East, South East, South West
Elevation: 10,000-11,500 ft

Avalanches: No new avalanches observed since Christmas cycle.
Weather: Cold temps (~5 to 10*F). Calm to light westerly winds. Light snowfall tapered late afternoon, about an inch of accumulation during the day. Overcast to broken skies.
Snowpack: 5 or 6 rumbling collapses below about 10,200 feet, becoming quieter as we gained elevation to near treeline. One pit on an ESE slope below treeline had 85 cm of slab over fist hard facet layer. The slab was 1F in hardness near the bottom, up to fist hardness at the top, leaving a sense of “It feels good and stable” while skinning. 3x propagating results in ECT, moderate to hard, Q1 SC. Another pit on a SW aspect near treeline showed a 100 cm slab over a thin, friable crust (1cm thick, 1F hard), over a fist hard facet layer. Slab collapsed on isolation (ECTPV) on first test and after 30 taps on second test (ECTP30 Q1, SC). Quick pit in an old bedsurface from Christmas cycle on an E aspect near treeline showed a mix of meltfreeze crusts and pockets of old facets at the ground, with about 45 to 50 cm of recent snow above, 4F to F hardness.  See VIDEO

Hand hardness profile on ESE aspect below treeline. Repeated propagating failures near the ground on fist hard facets

IMG_5414

Mountain Weather 12/30/15

CB Avalanche CenterWeather

Date: 12/30/2015

A broad trough is stretched across the western half of the country, centered to our south. This is feeding cold, arctic air into the state. Shallow moisture arrives under a weak shortwave today, bringing light snowfall to the Elk Mountains. Another shortwave moves overhead tonight, with additional flurries and reinforcing cold air. The western edge of our forecast area could see upwards of 6″ or 8″ out of this disturbance, with an inch or two on tap for the mountains near and east of town.

Baldy SW Shoulder/Elkton

CB Avalanche Center2015-16 Observations

Location: Paradise Divide Area
Date of Observation: 12/28/2015
Name: J Banks
Subject: Baldy SW Shoulder/Elkton
Aspect: South, South West, West
Elevation: 9,500-11,600ft

Avalanches:
Weather: Calm to light in general, gusting to Moderate NW winds on Ridgetops
Snowpack: SNOWPACK/AVALANCHE OBS:
No signs of instability.
HS 100-130cm
6-10cm 4F+ windslab only on the ridgetop @ 11,600
ski pen 10-15cm
Evidence of heavy wind scouring along the high elevation ridges (12,0000 and up) from NW/W loading onto E/SE

Slate River NTL/BTL obs

CB Avalanche Center2015-16 Observations

Location: Paradise Divide Area
Date of Observation: 12/29/2015
Name: Evan Ross
Subject: Slate River NTL/BTL obs
Aspect: North East, South East, South
Elevation: 9,000-11,400

Weather: Occasional light snow flurries, mostly cloudy sky, calm wind.
Snowpack:

South, Southeast BTL
Due south slopes had a nice 1-2cm crust at the surface on slopes generally over 25 degrees, while these crusts started to fade as you moved to southeast slopes. BTL, the snowpack consisted of the Christmas storm snow sitting on the ground. Around 10,300ft and above, this same storm snow was sitting on a variable soft crust just above the ground, surrounded by facets. Here HS was about 50cm and one column test produced a CT4, sudden but irregular fracture. This snowpack structure looked concerning but was variable and inconsistent across the slope. We traveled on these slopes for a long time at about 35degrees with no other obvious instabilities observed. Also, didn’t observe any structure at NTL south or southeast start zones.

Northeast NTL/BTL
Observed widespread old natural avalanches in start zones spanning east to north. After a short tour across a few avalanche paths, it seemed some 80% of avalanche terrain had already released down to the facets near the ground during the last cycle. Most of the hang fire that was left had already cracked and buckled. We traveled across a few pieces of hang fire where the structure remand very concerning, while the avalanche problem felt very stubborn. Only one collapse was observed while in these areas. Just below a crown at 12,300ft the HS was about 45cm with about 35-40cm of that as unconsolidated new snow that would have fallen during the later half of the Christmas Storm.

East River

CB Avalanche Center2015-16 Observations

Location: Crested Butte Area
Date of Observation: 12/29/2015
Name: Zach Guy
Subject: East River
Aspect: North East, East, South East
Elevation: 9000-9,600 ft

Avalanches: About 10 natural avalanches observed in this area from recent cycle on SE, E, NE aspects. SS-N-R2-D1.5-O.
Weather:
Snowpack: Short tour, got 2 large, rumbling collapses in flat terrain and numerous localized collapses. Persistent slab is thinner here, 14-18″ on average. Supportive on skis but easy to penetrate through to weak layer. Seems like propagation potential only exists where slab is a little thicker or stiffer, otherwise collapses wouldn’t carry across slope as slab fractured in thin spots.

Mountain Weather

CB Avalanche CenterWeather

Date: 12/29/2015

Light snow showers over the high peaks of the Elk Mountains began late yesterday afternoon and will continue through the morning today before tapering off as the jet dynamics move farther southwest. Minor disturbances will wash over Colorado tonight through Thursday, bringing occasional hits of light snow and upticks in westerly winds, before the last disturbance in the flow forms a closed low and finally allows the pesky high pressure to take hold of the western United States. Expect no more than a few inches of new snow by New Years Eve.

Carbon Tour

CB Avalanche Center2015-16 Observations

Location: Kebler Pass Area
Date of Observation: 12/28/2015
Name: kirk Haskell
Subject: Carbon Tour
Aspect: North East
Elevation: 12,000 ? not sure

Avalanches: No signs of current avalanche activity in the area we were skiing . Some old evidence of activity on steeper slopes .
Weather: Calm, partly sunny with high clouds
Snowpack: No signs of instability . Snowpack was quite supportable . Surface facets apparent from cold temps