Our January thaw continues with increasingly warmer temperatures, cloudy skies and steadier rain is forecasted for tomorrow. Temperatures have been quite warm on the mountain with a current and maximum temperature of 48 F (9 C) at Hermit Lake. In the past 24 hours the snow stake at Hermit Lake has dropped 8" (20 cm). Tuckerman Ravine is currently in the clouds but I have had good views into Huntington Ravine and the Hillman's Highway area this morning. None of the areas that I have been able to see have had recent avalanche activity and runnels from water channels under the snow have shown up. Brooks have opened up in many locations and some of the ice climbs and Huntington have water gushing out of them (Yale slab in particular). The Little Headwall is now an open brook and should definitely be avoided. If we were on a cooling trend right now I would feel quite comfortable with the stability of the snow, but we are not. Today's temperatures are already proving to be warmer than yesterday's and there was no significant cooling last night. That tells me that the volume of freewater in the snowpack will continue to increase through the day. As I explained in yesterday's advisory, warm temperatures are breaking down bonds that exist in the slabs and creating freewater in the snowpack. As this freewater percolates down into the snow it creates more warming and melting. All of this water will continue to move down through the snow until it reaches a barrier. The most prominent barrier in our current snowpack is a pronounced rain crust that developed from our last rain event on Christmas Eve. Since that time we have had quite a lot of snow and a number of avalanche cycles that ran on or above this rain crust. As free water moves through the snow and reaches this layer it will start to flow down hill and lubricate the interface of the slab above and its bond with the rain crust below. This process could produce natural avalanches in our current snowpack. The rain crust isn't the only thing that can act as a barrier. Water ice and dense slabs can do the same thing. Another concern is a stream forcing through the snowpack and ripping out a slab. This has historically caused some impressive avalanches in Tuckerman Ravine when the Cutler River swells and causes an avalanche near the Lip.

I discussed yesterday that these types of events are hard to pin down. It is all a matter of the snowpack having enough time to adjust to the changes that are occurring in a way that keeps the slabs in place and promotes long term stability. Sudden changes, like rapid warming, rain or a change in the flow of a water channel can overwhelm the stability in the snowpack and create avalanches. Snow stability tests in conditions like this don't give you very good information to predict the likelihood of a wet slab avalanche. The best indicator is the weather. With that said, one piece of useful information that I collected at our snow plot this morning was snow temperature. I was not surprised to find a reading of 0C (32 F) at the surface and 10 and 20 cm below the surface. It is worth noting that I got a reading of -2 C (28 F) 40 cm down and -1 C (30 F) 50 cm down and the snow in these locations was still relatively dry. It is a small piece of data in one location but it does make me think that cold slabs are still lingering under the warm saturated surface snow. Today's weather will continue to penetrate warm temperatures and water down into the snowpack and tomorrow will deliver rain which will continue to test the stability of the snow. Rain may give way to snow showers late tomorrow as a cold front brings us back below freezing. Until this occurs expect the avalanche danger to remain at Considerable. Friday's weather maker looks a bit warm for an all snow event. We'll wait and see how it progresses before speculating on how it will affect us in the mountains.

Two other points worth mentioning today. The first is to be aware of the potential for falling ice in the Ravines. The second is to bring snowshoes or skis if you plan on doing any traveling off the beaten path as post-hole conditions are spectacular right now.

THE LION HEAD WINTER ROUTE IS OPEN. This is a steep and challenging route for mountaineers. Crampons, an ice axe and the ability to properly use this equipment are recommended for safe travel on this route. The John Sherburne Ski Trail is open.