|Posted: 7:45 a.m., Tuesday, December 7, 2010|
This is an early season GENERAL AVALANCHE ADVISORY. A General Advisory is issued when instabilities are isolated within the entire forecast area. Use of the 5-scale danger rating system will begin when conditions warrant. Until then new advisories will be issued as needed. 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.
It looks like we’ve finally made the turn to winter and snowfields are growing in size. The summit has picked up 8″(20cm) of snow in December but until recently winds weren’t doing their part to push snow our way. This has changed as W and NW winds have ramped up and active transport has begun. The past few snow events have allowed local accumulations to vary widely so expect to find high spatial variability in the early season snowpack. As an example, Monday’s snowfall left more than a foot (30cm) of snow on the W side of the Presidentials while Hermit Lake received only 1.6″(4cm). At least the recent winds have been out of the W and will be moving snow across Bigelow Lawn and the Alpine Garden.
Through the next few days we expect to see lingering snow showers with cold air continuing to be ushered in from the north. Isolated pockets of snow will begin to connect and form small snowfields as we go through the dynamic transformation into full winter conditions. The size and distribution of snowfields changes daily under these patterns so one needs to expect a whole different ravine than when they visited the past weekend. Under a General Advisory you need to make your own avalanche stability assessments before venturing into any open slopes. Check www.mountwashingtonavalanchecenter.org frequently as we move through early December and certainly check for the latest avalanche advisory before heading into avalanche terrain.
We are now in early winter in the high mountains so remember that hiking trails going through ravines and gulfs will require mountaineering equipment and skills. Be aware that a small slab or sluff can be very dangerous if it is triggered in the wrong spot. This is particularly true for early season ice climbers. As a climber picks their way through a route they will usually cross small pockets of snow. Often this snow has been deposited over blue ice, making for a poor bond at the interface. Consider this ahead of time and place protection before crossing suspect slopes. Remember if a snowfield is big enough to recreate on, its big enough to avalanche.
Don’t wait any longer to refresh your avalanche skills. Pull out your beacon, install some fresh high quality alkaline batteries, and practice. Review your safe travel rules, techniques for assessing snow stability, and sign up for an avalanche course. We now have all the avalanche course providers in the valley this winter on our website, mountwashingtonavalanchecenter.org.
Justin Preisendorfer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856