Reported Friday, February 25, 2011 at 6:55 AM

Weather Forecast

Today:
Snow, 5-7", west southwest winds 15-25 mph gusting to 40 and a high near 30.

Tonight:
Snow, 7-9", west southwest winds 15-25 mph gusting to 40 and a low around 15.

Tomorrow:
Snow, 3-5", southwest winds 15-25 mph gusting to 40 and a high near 30.

Weather Outlook

A strong west southwesterly flow will bring snowy weather and gusty winds to the Elk Mountains today. Expect steady snowfall throughout the day with periods of locally heavy snow. Winds aloft back more to the south this evening and a moist southwest flow will continue to bring snow to Crested Butte through Sunday. Skies will begin to clear Sunday evening and drier weather will persist through Wednesday of next week.

Danger Rating

Extra Caution

The danger is CONSIDERABLE (Level 3) on Northwest through Southeast aspects at all elevations. Pockets of CONSIDERABLE (Level 3) danger exist in cross-loaded gullies and open bowls on South through West aspects at all elevations. The danger is MODERATE (Level 2) everywhere else.

Avalanche Problem #1

Wind Slab  
High
LIKELIHOOD OF TRIGGERING
 
Medium
AVALANCHE SIZE
 
Increasing Danger
Trend

Over a foot of storm snow in the high country and strong southwest winds have created fresh wind slabs on lee and cross-loaded terrain. Be most suspicious of northwest through east aspects near and above treeline but strong and swirling winds have the potential to load all aspects. While many windward slopes will be scoured by strong southwest winds, gullies and open bowls may be cross-loaded on south through west slopes. Wind transport won't be as strong at lower elevations but any rapid loading will stress the overall weaker structure of the snowpack below treeline. More snow and more wind are in the forecast today; anticipate sustained wind loading throughout the day.

Avalanche Problem #2

Storm Snow  
High
LIKELIHOOD OF TRIGGERING
 
Medium
AVALANCHE SIZE
 
Increasing Danger
Trend

So far town has received 8 inches of new snow in the last 24 hours and the mountains north and west of town have received well over a foot. Storm snow is resting on crusts on solar aspects and buried facets and surface hoar on shady slopes. Observers at Irwin reported minor cracking and very soft skier triggered slab avalanches running in the storm snow yesterday. Previous storm snow was low density--4% reported at Irwin. The incoming moist southwesterly flow will generate wetter snow and we will most likely be looking at an "upside-down" storm with heavy snow over lighter snow. Watch for the danger to rise with increasing snow throughout the day.

In the Backcountry

The town of Crested Butte recieved 5 inches of new snow overnight bringing the storm total to 8 inches early this morning. Irwin reported 10 inches of snow as of yesterday afternoon and by now the mountains north and west of town have received well over a foot of snow. While winds have remained relatively calm down here in town, ridge-top winds have been averaging 20-30 mph from the southwest with very strong gusts. More snow and strong west southwest winds are in the forecast today. Storm snow and strong winds have created dangerous avalanche conditions throughout the Crested Butte backcountry. Fresh wind slabs will be reactive on all lee and cross loaded slopes today. If the forecasted snow and winds verify we could be moving to HIGH danger this weekend. Avalanche conditions will worsen throughout the day and natural avalanches are possible on all aspects and elevations.

Deeper in the snowpack, buried surface hoar and facets are still present in the top 3-4 feet on shady aspects and crusts surrounded by weaker snow are buried on solar aspects. While these deeper layers have been relatively dormant so far this season, we could see them wake up with an increased load of snow this weekend. These layers are notoriously persistent and surface hoar that was buried in January is still showing clean and fast shears during tests. The potential exists to trigger large and destructive avalanches on these weak layers.

Travel Advisory

Skiers and riders should expect changing conditions throughout the backcountry today. We have already received enough snow and wind to raise the danger; with more snow on way today, the avalanche danger will continue to rise. With snow and wind increasing throughout the day, don't assume that the avalanche conditions will be the same on each run. Look for obvious clues of wind loading such as blowing snow, cracking, hollow sounding snow or if your tracks keep re-filling each run. Carful snowpack evaluation, cautious route-finding and conservative decison-making are essential out there today.

Reported by: MacKinnon