ACMG Mountain Conditions Summary for the Rockies and Columbia Mountains
September 17, 2009
A stable high pressure system with record breaking warm days and cool clear nights dominated the Rockies and Columbias over the last week. The fresh snow from early September has mostly melted off and as of September 16th only high glaciated terrain and upper elevation north aspects were still holding the snow.
All this changed today. The high pressure ridge started breaking down last night, and today (Sept. 17) the Rockies saw the arrival of rain showers and unsettled weather. Peaks along the Continental Divide got a dusting of new snow above 10,500 feet. No recent reports have come in from the Selkirks or Purcells, but unless you hear otherwise, I would expect a fresh dusting of snow on the higher peaks in these areas as well.
The forecast for the weekend is calling for a westerly flow with cooler temperatures, mixed sun and cloud, and showers in some areas west of the Continental Divide.
The alpine rock routes and ridges are mostly dry, but expect some snow on the rock at higher elevations. The alpine ice routes will have to be evaluated for rock fall potential, but the cool nights and bit of new snow sticking to the ice is starting to bring these routes back into shape. The key thing to keep in mind is that the weather is somewhat unsettled and, unlike the last week of perfect weather, there may be some afternoon build up and rain showers.
Weak snow bridges on the glaciers are still a significant hazard. Many of the crevasses will be covered over (and hard to see) by a thin layer of new snow, but the bridging strength of this snow will be minimal. Lots of probing and conservative route choices are in order on the glaciers at this time of year.
Brian Webster
Mountain Guide