Backcountry Avalanche Forecast for Vail & Summit County 
Issued 01/06/2010 6:57 AM by Brad Sawtell

Highlights

I am letting the Avalanche Watch expire as planned by noon today. I do believe our snowpack is weak 
but the increased load and stress  will come more from blowing and loading snow than new snow. Today 
as the jet nears, winds will increase and areas above treeline will likely not be too much fun. 
Temperatures will be cold even with out including the wind chill.

Avalanche Danger

The avalanche danger for the Vail-Summit County zone is CONSIDERABLE on N-NE-E-SE-S aspects near 
and above treeline, and on N-NE-E aspects below treeline on slopes steeper than 34 degrees. Weak 
basal snow, variable slabs, and recent windloading mean that human triggered avalanches are probable. 
Stability evaluation is challenging. On other aspects the danger is MODERATE, and human triggered 
avalanches are possible on steeper slopes.

Snow & Avalanche Discussion

It seems as though the winds materialized more than the expected snowfall. For that reason, I am 
letting the Avalanche Watch expire as planned, by noon today. That does not mean you can let your 
guard down.

Wind speeds have been blowing at consistent speeds along the high peaks and ridge tops and mostly 
coming from the West. As of this morning, temperatures have not gotten too cold yet, but when you 
add in the wind chill, it's cold!

We have heard of many avalanches over the last few days. It seems that the tally across the zone is 
well over 50 avalanches and it's close to a 50/50 split of natural and human triggered slides. Most 
of the natural avalanches were observed with the aid of the Flight for Life helicopter while most of 
the triggered slides are the result of avalanche control work. Common themes from all the activity 
include: similar aspects, similar elevations and similar weak layer (the weak layer with many of the 
naturals is assumed). Most of the activity is occurring on slopes that face Northeast, East and 
Southeast. They are at and above treeline. And finally, the weak layer is large faceted or cup shaped 
grains, i.e. depth hoar. The diamond industry uses the saying "Diamonds are forever." In the 
avalanche world, facets are the diamonds of the snowpack. Meaning, they are here for the season and 
will continue to be a problem.

The avalanche problem is different across the zone, but the end result is the same danger rating. 
The western side of the zone is dealing with a deeper, less dense snowpack that includes an intact 
buried surface hoar layer. This is evident by seeing activity in open areas while experience none 
while in the trees. The snowpack here is still sitting above large basal facets. The eastern end of 
the zone has less snow that is mostly structured as stiff slabs over large basal facets. In both 
areas, we are dealing with facets, which will last the season. Facets are persistent, weak and feel 
like sugar. They do not bond and they are not trustworthy.

For now, tread lightly, be patient, use your slope inclinometer to avoid slopes steeper than 34 
degrees and avoid high consequence terrain.

Weather Discussion

Several weather features will influence the Northern and Central Mountains on Wednesday, while the 
southern zones are only minimally affected. Northwest flow strengthens today generating very strong 
above treeline winds especially along the Continental Divide. Moisture within the northwest flow is 
spreading light to moderate snowfall into the Northern and Central Mountains. The Steamboat zone 
may receive around a half foot of accumulation with lesser amounts for other locations favored by 
northwest flow. On Wednesday afternoon, a cold front moves south along the Front Range causing 
temperatures to drop sharply east of the Continental Divide. The cold air will also spill into the 
Steamboat zone and eastern portions of the Vail-Summit County and Sawatch zones this evening. 
Sub-zero temperatures are likely in these areas by Thursday morning. Skies clear overnight and 
remain clear through Thursday. Strong northwest winds continue for the usual locations near and 
east of the Divide, while speeds gradually diminish for other areas. Temperatures remain very cold 
over the Northern Mountains and east of the Divide. Mostly dry northerly flow keeps sunny but cool 
temperatures on Friday with wind speeds still strong along high Continental Divide locations. Weak 
high pressure ridging will moderate temperatures and wind speeds for the weekend.