Colorado Avalanche Bulletins

This bulletin is from the CAIC, which is an agency of the State of Colorado.

Colorado Avalanche Information Center (CAIC) Advisory

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Issued 03/18/2010 5:55 AM by Scott Toepfer

Highlights

One more warm day before the next storm system arrives from the north tonight. On Wednesday temperatures got very warm above treeline, but little slide activity was reported. For today the threat of wet slide activity returns, especially since overnight lows remained fairly warm.

Our primary concern would be for the near and below treeline elevations...solar aspects. That threat ends for the time being by Friday as temperatures plummet. There was a deeper fresh natural soft slab on a north aspect near Ike Tunnel on Wednesday too. Above treeline, 250 feet wide, around 3 feet deep. Interesting.

At this time snowfall looks to favor the west tonight, and the east side on Friday.

threat. Friday slide pattern changes with new Wx system

The avalanche danger for the Front Range zone is Complex. It will change again on Friday. Pockets of exist on terrain 35 degrees and steeper where fresh wind loading from easterly winds is found. Look for fat convex pillows. Also as temperatures warm expect some wet slide activity, especially human triggered. On the cooler aspects near and above treeline look for these pockets of on terrain 35 degrees and steeper, and where the snow pack is less deep, like shallow buried skree fields, exposed rock outcrops, and wind scoured ridgelines, both horizontal and vertically running.

Snow & Avalanche Discussion

One more day of wet slide threats, especially from the SE-SW-W aspects as the sun makes its circuit around the horizon. Tuesday and Wednesday's warmth got some water percolating into the snowpack as temperatures jumped above freezing. A good freeze on Tuesday night helped, but the freeze Wednesday night was not so strong. The cooler northerly aspects remain complex and more winter like. Observation from Tuesday still mention some large collapses near treeline, an indicator that deeper weak layers still respond to loading and are prone to failures. Observations from Wednesday reported one fresh soft slab on a N aspect, estimated at 1-3 ft deep and 250 feet wide.

The snowpack is complex as we continue a slow transition to a spring pattern from a winter pattern. If you dig a lot of holes you will see a great deal of variability. There are still fresh natural soft slabs being reported, and we are also anticipating some shallow wet slide activity. People are pushing some of the bigger lines, which under most circumstances will be fine, however, as you know, if something breaks deep it has the potential to propagate wide and these can be difficult to get off of if you are center punching. Consider the consequences of a ride too. If you are swept into trees, through rocks or over cliffs things can suddenly get ugly.

The threat for wet slide activity ends on Friday. Easterly winds Friday could be building some fresh slabs on westerly aspects just like the last storm system.

Weather Discussion

A complex weather system is dropping southward from Canada today. This means our tables in the details section are not going to get all the info in so reading the text below for specifics will help see a pattern....of sorts...Might be a good idea to check out the afternoon weather update too...This weather system is a tough one.

One more warm day, close to as warm as Wednesday when temperatures were above freezing at 14,000 ft in numerous locations. Increasing afternoon clouds and winds will help suppress a complete melt-down this afternoon. Next comes the hard part...The short wave trough slips into northern Colorado near sunset, Winds shift from WSW across the west slope to easterly on the east side of the Divide around 10 pm...

getting east slope snowfalls underway. Winds along and just west of the divide are confused but eventually trend easterly, remaining more northerly further west. On Friday they trend easterly which makes it tough for snowfall accums west of the Divide.

In the Central zones winds become more NW overnight, and upslope easterly winds get underway around mid-morning Friday. Further west winds are WNW but the atmosphere seems a little moisture starved.

In the San Juan moisture looks to arrive around 3 AM with winds shifting from SW to NW overnight. This pattern favors the northern portion of the zone. These winds remain NW Friday except the Sangre's which switch to easterly mid-morning.

All zones see high temperatures early Friday morning with colder air following for some chilly daytime highs. As winds become easterly they should increase along the Divide, Sawatch, Steamboat and the Sangre's.

Models don't show anything big, but the downslope component could bring some 50 mph gusts at times.

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