November 29th, 2014

CB Avalanche CenterWeather

24 Hour Weather Outlook

Weather Discussion: Today will be another mild day compared to the last few. High temperatures will drop a couple of degrees and winds will increase as the atmospheric pressure gradient tightens. Sunday afternoon, a weak shortwave will pass to our north increasing cloud cover. Unfortunately this is only looking to bring precipitation to Northern Colorado. Starting Monday another ridge builds taking us back to dry and mild weather. The next chance for a change looks to be around Thursday.

Temperature: 38
Wind Speed (mph): 15-25 G40
Wind Direction: SW, W
Sky Cover: Mostly clear
Snow (in): 0

48 Hour Weather Outlook

Weather Outlook Summary:

Tomorrows Temperatures: 32
Tomorrows Wind Speeds (mph): 10-20 G30
Tomorrows Wind Directions: SW, W
Tomorrows Sky Cover: Few Clouds
Tomorrows Snow (in): 0

Natural Persistent Slab

CB Avalanche Center2014-15 Observations

Name: Evan Ross
Title: Natural Persistent Slab
Location: Paradise Divide Area
Date of Observation: 11/28/2014
Aspect: South East
Elevation: 9,800-11,800

Weather: Mostly clear sky, calm winds with a few gusts at ridgeline and air temperature near or above 40 degrees.

Snowpack: Many slopes from south east to south to west had a moist snow surface at all elevations traveled.. The snow surface has seen lots of settlement over the last few days and become much more dense. Even on a north facing slope at 10,500ft with dense trees where ski penetration was around 10-20cm.

No instabilities were observed on a 36 degree south slope while traveling and skiing around 11,000ft. See attached snowpit profile below.

Avalanches: Observed 2 natural persistent slabs that failed on the 11/22 interface, around noon on south eastern slopes with crown elevations at 11,800ft.

SS-N-R2-D2-O. Crown width about 300ft wide averaging 12 inches deep. See attached profile and pictures below.

SS-N-R1-D2-O. Crown width about 80ft wide averaging 12 inches deep.

Pit dug on a similar slope and elevation to a natural avalanche on 11/28/14. SS-N-R2-D2-O. (Click title to see Profile)

The weak layer. 2mm facets on a 1cm crust.

Natural persistent slab avalanche that failed on the 11/22 interface, around noon on a south eastern slope with crown elevation at 11,800ft. Crown width about 300ft wide averaging 12 inches deep. SS-N-R2-D2-O.

November 28th, 2014

CB Avalanche CenterWeather

24 Hour Weather Outlook

Weather Discussion: Not a whole lot of excitement in the weather forecast unless you like warm and sunny as that’s the general format into next week.. Winds will increase slightly on Saturday ahead of some Pacific moisture moving into Colorado on Sunday. Northern Colorado may eek out a few inches of snow but we’re more likely to just see increased cloudiness in our area. Heading into next week currently looks to stay dry with above average temperatures.

Temperature: 42
Wind Speed (mph): 10-20
Wind Direction: SW, W
Sky Cover: Mostly clear
Snow (in): 0

48 Hour Weather Outlook

Weather Outlook Summary:

Tomorrows Temperatures: 40
Tomorrows Wind Speeds (mph): 15-25
Tomorrows Wind Directions: SW, W
Tomorrows Sky Cover: Few Clouds
Tomorrows Snow (in): 0

November 27th, 2014

CB Avalanche CenterWeather

24 Hour Weather Outlook

Weather Discussion: Dry weather is moving in just in time so everyone can get out, play hard, and eat a bunch of turkey. A weak high pressure ridge with the jet stream just to our north will be responsibly for mostly clear skys and gusty winds through the weekend.

Temperature: 40
Wind Speed (mph): 10-20
Wind Direction: W
Sky Cover: Few clouds
Snow (in): 0

48 Hour Weather Outlook

Weather Outlook Summary:

Tomorrows Temperatures: 40
Tomorrows Wind Speeds (mph): 10-20
Tomorrows Wind Directions: W
Tomorrows Sky Cover: Few Clouds
Tomorrows Snow (in): 0

New Website: Avalanche Problems

CB Avalanche CenterAvi Blog, Avi-Off-Season

Zach Guy
Forecaster, CBAC 

By now, you’ve probably noticed the CBAC has had a bit of a make-over.  We have spent over a year designing, researching, redesigning, and coding our new website, which we launched this week.   We were operating on an old dinosaur of a web platform and it was time for a new site that matched the current state of the e-world.  This new site has improved graphics, higher resolution imagery, more user friendly from our end and yours, an improved observations platform, a format that is more consistent with avalanche centers nation-wide, and some additional forecasting tools which you can use to make safer decisions in the backcountry.  Bear with us as we work through the kinks and strive to improve the functionality of the site.  

Now let’s jump into a key element of our daily forecasts: the avalanche problem.  The reason we put a lot of focus on avalanche problems is because the flavor of the avalanches we expect to encounter can be more influential in our terrain and risk management than a given danger rating.  For example, not all Moderat danger ratings are created equal.  I move through terrain and make snowpack assessments very differently for a Moderate danger when the only concern is wind slabs, versus a moderate danger involving deep persistent slabs.  The Utah Avalanche Center just published a new tutorial on avalanche problems; its worth a look.  http://utahavalanchecenter.org/avalanche-problems-tutorial.  The CAIC also defines each problem here


This idea of avalanche problems is nothing new to our CBAC users, but we’re presenting it in a slightly different way. The four key elements to the avalanche problem is the avalanche character, its distribution, its likelihood, and its size.  Here’s an example of how we present the problem. You can always click on the little blue “information” icons for more help or info.


The trickiest part of this is the distribution rose: where the problem is located across our terrain.  Imagine a conical shaped peak, and you are hovering above it in your private helicopter.  The inner-most rung is the highest elevation: above treeline, and the outer-most rung is the base of the cone below treeline.  Each triangular octet represents a compass direction, so imagine this conical peak is oriented the same way it would look on a map. Now here’s the important part.  We shade the areas where the problem is most likely.  The problem distribution is never as black and white as it appears on this rose.  This gives you general guidance on where you are most likely to encounter the problem at the regional level, but it is still up to you to make assessments on individual slopes.  Here’s an example: We get a mild snow event with strong westerly winds. Our advisory will probably shade the distribution of fresh wind slabs on leeward aspects (NE, E, SE) near and above treeline because windslabs will be fairly widespread on those slopes.  Given such an event, I can almost always find wind slabs on windward aspects (due West) too, if I seek out cross-loaded features or gullies.  There might be a few slopes below treeline that develop wind slabs as well.  So just because the wind slabs are prevalent on higher elevation, leeward aspects, it doesn’t mean you shut off your snow senses if you’re traveling elsewhere.  We will try to describe these nuances and subtleties in our text, so its in your best interest to read the whole advisory and not just look at the pretty pictures.  

The likelihood is fairly self explanatory.  This is the chance of triggering a slide if you are recreating in steep, avalanche terrain in the parts of the rose that we have shaded, where the problem is most prevalent.  Lastly, we describe the expected size.  Small avalanches are D1’s: relatively harmless to people unless they push you into a terrain trap. Large avalanches are D2’s: they could bury, injure or kill a person. Very large avalanches are D3’s: these could bury cars, destroy a house, or break trees. Historic avalanches are nearing the maximum size a slope can produce. These don’t happen every year.  

We’d like to acknowledge Brandon Clifford, our website designer, and the CAIC for contributing resources and forecasting elements.  We hope you find our new website useful in planning and making safe decisions in the backcountry.

11/26/2014

CB Avalanche Center2014-15 Observations

Name: Evan Ross
Location: Paradise divide area
Date of Observation: 11/26/2014
Aspect: North East
Elevation: 10,000-11,500

Weather: Clearing sky, generally warmer temps then pervious days, west northwest winds gusting strong enough to continue drifting snow at near and above treeline elevations.

Snowpack: Last weekends storm snow was wind buffed and consolidated into a more cohesive slab.  This slab was still fist hard but noticeably more consolidated then previous days. This didn’t seem to affect the outcome of stability tests in the same areas as tests from previous days on the same slopes. Collapsing has decreased from previous days as well, but ECT test still show the potential for avalanching of the persistent slab and week fasted snow on the ground.

Avalanches: 1 natural wind slab within the 48 hours failing on an above treeline cross loaded Southern slope. SS-N-R2-D2

Irwin Snow Obs

CB Avalanche Center2014-15 Observations

Name: Billy Rankin
Title: Irwin Snow Obs
Location: Kebler Pass Area
Date of Observation: 11/26/2014
Elevation: 10,200′

Snowpack: Irwin Storm total was 23″ w. 2.1″ SWE. Storm board was 17″ HS: 29″. There was a widespread rime crust this morning around 3-4 mm thick

2014/11/25

CB Avalanche Center2014-15 Observations

Name: Ian Havlick
Title: 2014/11/25
Location: Kebler Pass Area
Date of Observation: 11/25/2014
Aspect: South, West
Elevation: 10,500

Avalanches: n/a

Weather: S1-S3 snow throughout morning. definitely convective and orographic. light variable winds in all but the most open terrain where the local winds were moderate from the WSW.

Snowpack: 27″ settled snow on HS stake. 15″ settled storm total. 6″ new overnight. Stout MFcr on South and West aspects below treeline. couple pits showed failure under moderate loading steps just below MF crust mid-pack. cracking and one major collapse on below treeline, west-southwest facing slope, that was around 34 degrees in steepness.

11/25/2014

CB Avalanche Center2014-15 Observations

Location: Paradise Divide Area
Date of Observation: 11/25/2014
Elevation: 9,300-11,300

Weather: On and off snow showers producing about 3” of new snow between 9:30am and 3pm. Obscured sky throughout the day with strong enough NW wind to refill some tracks throughout the day but not strong enough to notice the blowing snow.

Snowpack: Snowpack: Found some wind stiffened snow but didn’t find a wind slab problem on the NE terrain at ridgeline. So the take home observations were, where in the terrain traveled was the persistent slab active? The snowpack needed to be deep enough to have a strong enough mid-pack to produce propagating test results. The mid-pack that has any strength is the 11/13 to 11/15 storm sitting over weak facets from earlier this season. This set up can be found down to 9,000ft west of Crested Butte. In this area, about 10,800ft seems to be the elevation where this mid-pack starts gaining enough strength to produce propagating results in snowpack tests that represent the potential for a persistent slab avalanche. Below that average 10,800 elevation on NE aspects the midpack could collapse and would only produce very small radius cracks, or ECTX test results. Above that elevation a pit dug with a 115cm snowpack and 4f-1f mid-pack produced an ECT21 SC and produced other collapses while touring with large radius shooting cracks. Thus, representing areas that could produce a persistent slab avalanche given the right slope angle and terrain feature.

November 26th, 2014

CBACWeather

24 Hour Weather Outlook

Weather Discussion: Since yesterday, 2-4” of additional snow fell around area bringing the prolonged storm totals to 15-20” of snow since Saturday, with 1.5 to 1.8” of water equivalent. Westerly winds have continued to remain elevated, with most remote weather stations showing gusts in the 25 mph range over the last 24 hours. Today, snow showers will gradually diminish by early afternoon as high pressure works into the area today, and takes hold through the weekend.

High Temperature: 25-30º
Wind Speed (mph):10 – 20 mph
Wind Direction: West
Sky Cover: Overcast becoming clear
Snow (in): Trace-1″

48 Hour Weather Outlook

Weather Outlook: The extended outlook looks mild and sunny through Thanksgiving, but another Pacific storm is taking shape and could bring another round of significant snow early next week.

Tomorrows Temperatures: 20-25º
Tomorrows Wind Speeds (mph): 5-15 mph
Tomorrows Wind Directions: W
Tomorrows Sky Cover: Mostly Clear
Tomorrows Snow (in):0″