Cooler temperatures overnight allowed the snow surface to re-freeze. The avalanche danger will start as LOW, but rise to MODERATE as the day progresses. In addition to increased potential for loose, wet avalanches later in the day, pay attention to slopes that could produce more destructive avalanches from cornice fall or glide cracks. Also, consider the lingering possibility of wet slabs before committing to steep, rocky, and exposed terrain.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
With the cooler temperatures overnight that re-froze the surface snow I expect the loose, wet problem to be managed like a more typical spring day. Head out early, and call it a day before the sun and warm temperatures break down the crust. Avoid sun exposed slopes and run-out zones when the snow surface becomes moist and you begin to sink deep into the snow when you step out of skis or off of your sled.
Recent warm temperatures and sunshine weakened the numerous large cornices in the area over the past week. Last Monday, we noted a large slab avalanche triggered by cornice fall on Mt. Cameahwait in the Flathead Range. When cornices hit the slope below they are capable of triggering deep weak layers that would otherwise remain dormant in the snowpack. Cornices can pull far back from behind the ridge line making it important to keep a safe distance away from the edge. Skiers on Great Northern Mountain on Thursday noted cornices that were pulling away from the ridges, and creating "cornice crevasses" (observation) further illustrating the importance of giving them a wide margin.
Glide cracks exist throughout the advisory area and we observed several glide avalanches. Even when the snow surface re-freezes water can continue to move through the snowpack so don't write glide avalanches off. Forecasters with the Going-to-the-Sun Road outside the advisory area noted recent glide avalanche activity on upper elevation north aspects (observation and image). Glide avalanches are very difficult to predict, so the best strategy is to avoid playing on slopes where glide cracks exist.
Even after temperatures drop below freezing free water can continue to move through the snowpack. Wet slab avalanches occur when melt or rain water weakens bonds below a slab. This most commonly occurs above a crust that can pool the free water, and can awaken previously dormant weak layers. These avalanches are difficult to predict. The best way to manage this problem is to avoid steep, exposed, and rocky terrain.
Additional Concern: Watch for lingering wind slabs at upper elevations. Cornices falling on previously wind loaded slopes could cause large avalanches, and it is still possible for humans to trigger wind slabs at the upper most elevations.
This is the last scheduled advisory of the season. Check back tomorrow as we will issue a spring avalanche statement. We would like to thank all of you who helped support the Flathead Avalanche Center this season. Have a great Spring.
Friday: The Going-to-the-Sun Road avalanche program reported new glide avalanche activity that occured between 4/7/2016 at 4:00 pm and 4/8/16 at 8:30 am. They also noted widespread loose, wet avalanche activity due to warm temperatures and a lot of sun (observation). Mark and I were on Ghoulie Point in the southern Whitefish Range and found moist surface snow on all aspects and elevations late in the day. A series of crusts in the upper-snow pack had water pooling above them on sunny slopes, and these crusts were decomposing on shaded slopes.
Thursday: The Going-to-the-Sun Road avalanche program reported substantial recent glide, wet loose, and soft slab avalanches just outside our advisory area in Glacier National Park (observation). Skiers on Great Northern Mountain in the Flathead Range observed a lot of recent and older avalanche debris on multiple aspects. They also noted large cornice that had begun to crack and formed "cornice crevasses" (observation).
Tuesday: The Going-To-the-Sun-Road avalanche program reported up to 7 inches of new snow at low elevations with small wind slabs forming above 5500 feet. Impressive wet loose debris on all aspects was noted from the weekends above freezing temperatures (observation).
Monday: We traveled to the Tunnel Ridge area in the Flathead Range we observed the aftermath of the recent wet loose avalanche cycle on all aspects at mid and upper elevations. We noted a large wind slab avalanche triggerred by cornice fall on Mt. Cameahwait (observation).
Visit our Observations page and our You Tube channel for more observations from the entire season.
Thanks to everyone for submitting observations. They are extremely useful and could help save lives.
HOW TO SUBMIT OBSERVATIONS:
Email: [email protected]
Call and leave a message: 406.387.3821
You can also submit quick observations via text: 406.241.4571 (FAC mobile)
OR
Submit Snowpack Observations: http://www.flatheadavalanche.org/node/add/snowobs
Submit Avalanche Observations: http://www.flatheadavalanche.org/node/add/avyobs
Yesterday, the area enjoyed another warm, sunny day with temperatures in the mid-50s to low-60s. A system east of the Continental Divide shifted winds out of the east and northeast and cooled us down. Currently, Mountain temperatures range from 26º-35º F, and winds are blowing out of the east and northeast at 5-13 mph with gusts to 30 mph. Today should see partly cloudy skies with temperatures rising to the mid-upper 40s. Winds will continue out of the east-northeast at 5-15 mph with gusts in the 30s, and stronger as you approach the Continental Divide.
| 0600 temperature: | 26-35 deg. F. |
| Max. temperature in the last 24 hours: | 45-61 deg. F. |
| Average wind direction during the last 24 hours: | WSW shifting E-NE |
| Average wind speed during the last 24 hours: | 5-15 mph |
| Maximum wind gust in the last 24 hours: | 20-35 mph |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 70-107 inches |
| Sunday | Sunday Night | Monday | |
|---|---|---|---|
| Cloud Cover: | Partly cloudy, cooler temperatures. | Partly cloudy. | Short-lived ridge of high pressure. |
| Temperatures: | 44-58 deg. F. | 27-34 deg. F. | 53-64 deg. F. |
| Wind Direction: | E | E | S-SW |
| Wind Speed: | 10-13 gusts 25-29 | 7-8 | 4-7 gusts 17 |
| Snowfall: | 0 in. | 0 in. | 0 in. |
| Snow Line: |
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
