April 3 Avalanche Advisory
Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for April 3, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide below to help you make more informed decisions regarding travel in avalanche terrain for the next few days. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle NF Avalanche Center website.
Weather and Snowpack Analysis
Winter refuses to release its grip on West Central Montana. Most SNOTEL sites received over 2 inches of snow water this past week translating to over 20 inches of new snow. High winds early in the week were moving a lot of snow around and by Wednesday we began hearing of human triggered avalanche activity in the Bitterroot Mountains. The ski patrol at Snowbowl initiated a few large slab avalanches with explosives Wednesday. Temperatures began warming Thursday and most mountain locations reached into the mid to upper 30’s. This warming helped further settle the new snow and we were feeling pretty good about stability on all but the steepest terrain. Wind loaded terrain is still spooky but we felt that would also stabilize after a few more hours.
Current Avalanche Danger
All Advisory area locations:
Above 6000 feet the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 6000 feet the avalanche danger is LOW, natural avalanches are very unlikely and human triggered avalanches are unlikely. Please consider that there is a great deal of local variation in snowfall amounts. Even under low to moderate avalanche conditions, you can find isolated pockets of unstable snow on some terrain features especially where wind loaded.
During periods of rapid warming:
The avalanche danger is CONSIDERABLE. Human triggered avalanches are probable, natural avalanches are possible. The first warm day or any amount of rain on all this new snow is going to be a dangerous time to be on or under any steep slope.
Weather Forecast and Avalanche Outlook
An upper trough will allow active convection through the day Friday. Snow showers will be widespread but short lived and not able to produce significant precipitation. Shower activity will begin to diminish Saturday and a warmer ridge will develop over the area Sunday bringing normal to above normal temperatures by the early part of the week.
Expect avalanche danger to improve during the next few days as the snow slowly adjusts to the recent heavy load. During periods of clear weather, pay close attention to how the sun is affecting the snow surface. The sun angle is now high enough that just a few minutes of direct sunlight can warm a slope rapidly enough to bring it down.
If you have any information you’d like to share or have questions about anything related to snow safety, please contact us at [email protected].
The Beacon Park at Lolo Pass is still available for use but on weekends only. The Lolo Pass Visitor Center is now on their spring operating schedule. Hours are 0800-1630 PDT Saturday and Sundays.
We will no longer issue regular avalanche advisories on Mondays and Fridays. We will post information statements as needed after April 1st.