Reported Tuesday, December 29, 2009 at 5:15 AM

Weather Forecast

Today:
Cloudy, trace to one inch possible by this afternoon, west winds 5-15 mph and highs in the upper 20s in Crested Butte and low 20s in Gunnison

Tonight:
Cloudy, 1-2 inches possible, west winds 5-15 mph and lows around 10 in Crested Butte and 5 in Gunnison

Tomorrow:
Cloudy, 1-3 inches possible, west winds 10-20 mph with gusts up to 25 mph and highs in the low 20s throughout the Valley

Weather Outlook

Another weak trough of low pressure moves through Colorado today and we should see cloudy skies, cool temperatures, increasing winds and a chance of snow by late this afternoon. There is more unsettled weather upstream of this system and we can expect continued snowfall through Friday as a stronger northwest flow digs into the state. Storm totals will be on the smaller side, but hopefully we will get enough snow each day to freshen things up around here.

Danger Rating

Elevated Caution

The danger is MODERATE on all aspects and elevations.

Avalanche Problem #1

Deep Slabs  
Low
LIKELIHOOD OF TRIGGERING
 
Large
AVALANCHE SIZE
 
Same
Trend

The avalanche danger is MODERATE which means that it still remains possible to trigger an avalanche today. Deep slab instabilities are still lingering out there and may be triggered from areas of shallow or weak snow. If triggered, deep slab avalanches have the potential to propagate large distances and be destructive.

Avalanche Problem #2

Wind Slab  
Low
LIKELIHOOD OF TRIGGERING
 
Small
AVALANCHE SIZE
 
Same
Trend

Last week's strong northwest wind has created shallow wind slabs on lee and cross-loaded aspects at all elevations. These slabs may be reactive to skier triggering but have limited potential to injure or bury a backcountry traveler due to their small size.

In the Backcountry

Not much has changed in the backcountry since yesterday; our snowpack still remains complex and variable. Warmer temperatures have helped with the bonding of shallow wind slabs, but lee and cross-loaded slopes may still have shallow unstable slabs resting on weak surface forms. Our cohesive mid-pack remains a slab resting on a weak faceted base and a reported skier triggered avalanche from Marble this weekend indicates that deep slab instabilities still exist. The skier triggered a large avalanche above tree line on a northeast aspect on a slope that already had several tracks in it. The avalanche was triggered from an area of shallow snow and this serves as a reminder that our mid-pack is variable in depth and strength across terrain. Southerly slopes have a semi-supportive sun crust with facets above and below the crust. It has been almost two weeks since our last significant snowfall and many repeated cold and clear nights have created widespread surface hoar and surface facets. Both of these persistent weak layers may be reactive after this week’s storm.

Travel Advisory

Backcountry users still need to remain vigilant about monitoring snow depth and avoiding areas of shallow and weak snow. Deep slab instabilities are lurking out there and the best way to avoid them is to choose appropriate terrain that avoids trigger points and shallow deficit zones. If you are out in the backcountry today, pay attention to surface forms such as surface hoar and surface facets as these persistent weak layers may be buried and preserved after the next couple days of snow.

Reported by: MacKinnon