last update of the season. The following are some helpful hints to guide you in your spring trips to the mountains. Our
sincere thanks to the Friends of IPAC for their support. This center greatly depends on the support of you, those who send in observations, helped to fund the Abromeit Avalanche Scholarship, and donate time to help with classes, thank you. We had another great winter of collaboration on avalanche classes and you can count on us continuing and
expanding that in the future. IPAC would also like to thank Tom Eddy for keeping us informed of numerous weather and avalanche events from the southern Selkirks. Thanks to Bill Williamson who helped us kick off the Abromeit Scholarship. Thanks to Pat Gunter for helping me with avalanche investigations and getting me up to Gem Lake on a big powder day. We all enjoyed working with you and we have big plans for classes and events next winter.
SPRING TOURING/RIDING TIPS
Spring is generally a safe time to travel in the mountains but there are some rules to live by. The safest and
best conditions will exist after a good nighttime freeze. Dig a pit to see how deeply the freeze penetrated. This will
give you an idea of how quickly the snow will become slushy and unstable. Get on the slopes early before the
temperatures get too warm or the sun gets too intense. Mountain temperatures above 50 degrees should be an indicator
that conditions are becoming unstable. Strong radiation can penetrate deep into the pack and destabilize weak layers.
Steep south facing slopes are affected most rapidly by strong sun. Steep East facing slopes are the first slopes to get morning sun and soften up. If you are into the slush up to your boot-tops or you’re laying on the throttle to move its time to get off the slope. By planning your route to take you to slopes just as they come into the sun and begin to thaw you can enjoy good, safe sliding. Always be careful around rock outcroppings because they hold heat and weaken the snow for some distance around them. Rain always weakens the snow pack and this time of year rain can lubricate ice crusts making the overlying layers more prone to slide. When we do get new snow watch for the type of surface it is bonding to. New snow on an ice crust that is experiencing melting during the day can be extremely unstable, especially if it is wind-loaded. In general, new snow will be more sensitive to radiation. Surface hoar can also be a weak layer in the spring so check under the new snow accumulation to make sure you’re not dealing with that little devil. Finally, keep track of extended periods of thawing, not only during the day but most importantly overnight. This will also decrease snow stability. Night-time temperatures below freezing are a must for good sliding conditions, and safe sliding conditions. The more nights in a row that freezing conditions occur, the more stable the snow is likely to be. Freezing conditions will usually accompany clear nights while overcast nights tend to trap heat.
In the high country the Panhandle is averaging around 96% of an average peak snowpack and the Clearwater region is
much higher at about 129% of an average peak snowpack this year. The Spokane drainage is doing well too with 105%. Bear Mountain snotel shows 11 feet, Schweitzer is at 10 feet, Hidden Lake with 8 feet, Lookout Pass has 6 feet, and Lost Lake is the winner with 12 feet of snowpack. Low elevation snow is restricted to cold drainages and north aspects so expect long approaches on many trails, and driving a ways in on forest roads and some dirt riding on your snowmobile. Once you're up there, south aspects are already thin on snow so they will tend to melt out early this year. Be careful of rotten snow and falling through in some deep holes on south aspects. The thick crusts in the upper pack will tend to concentrate radiation and result in rapid destabilization of the upper pack over the crusts and free water lubricating potential slabs. Big wet slabs on steep terrain may be a bit more of a hazard this spring because of solar heating over the thick crust. Weak layers below the bridging crust should be locked in place until the pack melts enough to where the sun can effect it. On your ventures into the high country remember to respect old terra firma, the brown stuff, that sticks to your boots and tracks on the way up. Don’t rut up the roads and trails in your truck or ATV trying to get an extra 100 feet. Park before you get to the muddy sections and try to avoid them as much as possible. Just like your tracks in the snow, leave no trace.
It sound like the next few days hold snow in the forecast with possibly 3-5 inches of accumulation at the higher
elevations. Winter weather may persist into next week so be thinking about potential slab avalanche conditions with
new snow and for a 24 hour period after the storm. Check to see if the new snow is loading up over a layer of surface
hoar. Eric Morgan was high up in the Selkirks this week and he found powder on a north aspect. Like we indicated in
last weeks advisory, be checking the upper pack above the thick ice crust in the short term as most stability issues will
be related to this layer. Once it is gone, melted out or consolidated, you’ll be looking at deeper crust layers, old
surface hoar, and finally the weak base, but I’ll bet you’ll be long into you mountain bike or 4-wheeler by then. Have
a great spring. We’ll be back next year with the first winter snows.
Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess
current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers
can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and
exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche
rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid
Have a safe and pleasant Spring.