|Posted: 8:15a.m., Sunday, December 12, 2010|
This is an early season GENERAL AVALANCHE ADVISORY. Use of the 5-scale danger rating system will begin when conditions warrant. A General Advisory is issued when instabilities are isolated within the entire forecast area. However, it is important to realize that avalanche activity may occur before the issuance of a 5-scale forecast. Under a General Advisory you need to make your own snow stability assessments when venturing into avalanche terrain.
As is often the case with Mt. Washington, manic weather will dominate the coming days. Conditions will change rapidly and the mountain hazards of concern will switch from those of winter to spring to winter again! We expect temperatures to rise with snow transitioning to rain and freezing rain at the summits by Sunday evening before a return to more seasonable conditions during the workweek. Despite the quickly approaching holidays we have remained under the General Advisory flag because isolated snowfields have yet to connect and form the defined avalanche tracks for which we regularly forecast. Nonetheless we expect that there will be localized avalanche activity during this forecast period with an abundance of precipitation on the horizon. Stability concerns will result from the rain-on-snow event forecasted for Sunday into Monday, as well as from the snow that will accompany the cold front expected to push the warm, wet weather out of town. Be aware that a small avalanche can be very dangerous if it is triggered in the wrong spot. Snow that has been deposited over blue ice often is very poorly bonded at the interface. Ice climbers should consider this ahead of time and place protection before crossing suspect slopes. Spatial distribution of these snow-on-ice conditions will increase when the snow comes in behind the rain and dropping temperatures.
Ice conditions have generally been excellent for climbers and fortunately I don’t believe that the forecasted rain will be enough to hit the reset button. Icefall is likely to occur Sunday into Monday morning around both ravines as smaller and unsupported pieces of ice come crashing down. What doesn’t succumb to the combination of warmth and gravity will need some time to heal before climbers jump back on the horse. I would expect significant undermining to occur from the rush of running water creating detached ice that may also form ice dams as temperatures drop during the workweek. A little extra caution and some rock gear might help for safer, more enjoyable climbing as routes are restored to health by midweek.
We are now in early winter in the high mountains so remember that hiking trails going through steep terrain will require mountaineering equipment and skills. Don’t wait any longer to refresh your avalanche skills. Practice with your beacon, review your safe travel rules and snow stability tests, and sign up for an avalanche course.
Justin Preisendorfer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856