Special Advisory Statement: Significant amounts of new snow combined with a warming trend will create dangerous avalanche conditions into the weekend, especially on Saturday. Natural loose wet avalanches will become likely under rising freezing levels and direct sunshine (see video). With snowfall in excess of 20" in higher terrain, these slides can entrain dangerously large volumes. Watch for rapidly changing conditions and be mindful of overhead hazards if you are traveling in the mountains this weekend.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
As daytime temperatures climb, fresh snow from the past few days will easily shed off of steep slopes in the form of wet point release avalanches. Human triggered and natural avalanches will become likely during day time warming on Friday and Saturday, especially if we see periods of prolonged sunshine. On slopes that hold more than a foot of recent snow, or in long running terrain features, these slides will be large enough to bury you. Avoid traveling underneath gullies or steep terrain if you see rollerballs, pinwheels, or adjacent avalanche activity.
1 to 2 feet of storm snow has formed fresh storm slabs at mid and high elevations. You are most likely to encounter this problem as you move higher in elevation towards colder, more wind-affected snow. Watch for cracking and clean sheers in the new snow to hint at instabilities, and be wary of steep rollovers or thicker wind drifts.
Observers on the Going-to-the-Sun Road and in the Middle Fork reported 20 inches of storm snow on Thursday, with numerous large debris piles below steep terrain. Since Wednesday morning, Noisy Basin SNOTEL is showing 4" of Snow Water Equivalent, Big Mountain has picked up over 20" of new snow, and Stahl Peak SNOTEL is at 12" and counting. I'd estimate some of the highest alpine terrain has picked up as much as 3 feet of fresh snow. Wow! Double check your calendar. It's not April Fools' Day. As a matter fact, it's almost a month later than that, which means once the temperatures rebound to seasonal norms this weekend, and if the high almost-May sun angle strikes all this fresh snow, we are going to see a noteworthy wet loose avalanche cycle. Keep your head on a swivel as you travel through the mountains over the next few days, being especially wary of the steep slopes above you holding on to copious amounts of fresh snow. Roller balls and pinwheels are Mother Nature's warning sign before she unloads a cement mixer full of wet heavy debris down on you. You want no business getting tangled in one of these types of slides. I suppose it's a faux pas to carry a beacon, shovel, and probe on your road bike ride, but being avalanche aware on freshly plowed pavement at a higher elevations is not a bad idea this weekend.
Numerous D1.5 to D2 natural avalanches ran on Thursday in the Middle Fork (see video) and along the Going-to-the-Sun Road; these appeared to be loose and wet loose avalanches involving the fresh storm snow, from 12" to 20" thick. On Thursday, backcountry travelers reported easily triggered wet loose avalanches at mid elevations in the Middle Fork and a reactive snowpack on steeper terrain at Whitefish Mountain Resort.
In the wake of a large trough carving eastward across the West, we will see showery snowfall under cool, northwest flow on Friday. Look for afternoon warming to cause convective pulses late Friday, before a short-lived ridge brings warmer and drier air on Saturday. Partly cloudy skies on Saturday morning will give way to increasing clouds ahead of another round of moisture on Sunday.
| 0600 temperature: | 26-31 deg. F. |
| Max. temperature in the last 24 hours: | 31-35 deg. F. |
| Average wind direction during the last 24 hours: | WSW |
| Average wind speed during the last 24 hours: | 5-12 mph |
| Maximum wind gust in the last 24 hours: | 22 mph |
| New snowfall in the last 24 hours: | 3-20 inches |
| Total snow depth: | 15-133 inches |
| Friday | Friday Night | Saturday | |
|---|---|---|---|
| Cloud Cover: | Mostly cloudy skies with intermittent snow/rain showers | Lingering snow/rain showers under mostly cloudy skies | Mostly dry weather under mix of clouds and sun. |
| Temperatures: | 38-46 deg. F. | 27-32 deg. F. | 40-50 deg. F. |
| Wind Direction: | WNW | WSW | SW |
| Wind Speed: | 3-5 | 3-5 | 4-8 |
| Snowfall: | 0-2 in. | 0-1 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.
