The cold temperatures and clear skies overnight formed a firm snow surface. The morning sun will have a tough time breaking down this crust before the clouds roll in. The avalanche danger is LOW this morning, but warming temperatures and light rain in the afternoon will elevate the danger to MODERATE at low and mid elevations. Pay attention to signs of a weakening snow surface like roller balls forming on steep slopes, and of course, rain on the snow.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Cold temperatures and clear skies overnight created a firm snow surface. We should see the sun for a couple of hours today, but I don't expect it to be around long enough the break down the stout crust. However, warming temperatures and a bit of low to mid elevation rain in the afternoon will start to weaken the surface snow and increase the potential to trigger a loose, wet avalanche. Watch for early signs of instability like roller balls forming on steep slopes and rain moving in earlier than expected.
Giant cornices exist along most ridgelines across the advisory area. It's important to pay attention to what is looming above you given the unusual size and how overhung many of these cornices are. Keep a good distance from these while traveling along ridge lines as they can pull out further back than expected, even behind the solid ground. When a large cornice falls it has the potential to trigger deep instabilities that would otherwise remain dormant resulting in a large avalanche. Glide cracks have also been observed opening up in many locations. There is a large amount of uncertainty associated with glide avalanches, so the best way to manage them is to avoid slopes where they are present. Over the past week, we've seen the variability of spring weather in the mountains. We observed large natural avalanches last week (3/14-3/15) and Saturday (3/18) sliding on the Feb. 10 crust associated with rain at upper elevations. The Feb. 10 crust has weak sugary snow (facets) sitting on top of it in many locations and, although buried up to 4 feet deep, may continue to pose future issues. Dig into the snow to assess the slab atop the Feb. 10 crust. When we dig into our current snowpack, it tells a story of past powder days, a bit of wind, a whole lot of rain, and some clear temperature shifts. Each of these events that slowly shaped our snowpack throughout the season can come into play within one single day during the spring. Awareness of rapidly changing conditions is vital while enjoying the longer spring days in the mountains.
Thursday: Snowboarders in Skiumah Creek in the Flathead Range and found a saturated snow pack below 5400 feet. They found a supportable surface crust above 6000 feet and noted thin pockets of recently wind drifted snow.
Wednesday: We were in Noisy/Jewel Basin in the Swan Range. The snow level in the morning was at about 6000 feet and climbed to 6500 feet as the day progressed. We found 2-3 inches of overnight snowfall that became moist mid-day. At elevations above 7000 feet an ice crust on the surface remained supportable through the afternoon. We dug a snow pit at 6800 feet on a northwest facing slope and found that recent rain and melt-water only percolated through the upper 40 cm of the snow pack. Just 500 feet below in another snow pit at 6300 feet we found wet snow all the way down to a decomposing Feb. 10 rain crust. Light wind with moderate gusts at upper elevations only drifted the overnight 2-3 inches of snow, but we noted very large cornice development from previous storms.
Tuesday: BNSF Avalanche Safety reported warm temperatures and mostly clear skies in the John F. Stevens Canyon. They found a mostly isothermal snowpack in a pit at 6350 feet on a south aspect but were able to get an ECT to propagate with moderate force about 40 cm from the surface.
See below for all observations this season.
The sun finally broke through the clouds late yesterday afternoon and with clear skies overnight the temperatures dropped well below freezing. Currently, temperatures above 6000 feet range from 20-26ºF, and winds are out of the southwest at 5-9 mph. We should see a couple of hours of sun this morning before the clouds move into the region ahead of another system. Light showers develop this afternoon and become more widespread tonight.
| 0600 temperature: | 20-26 deg. F. |
| Max. temperature in the last 24 hours: | 26-37 deg. F. |
| Average wind direction during the last 24 hours: | Southwest |
| Average wind speed during the last 24 hours: | 5-15 mph |
| Maximum wind gust in the last 24 hours: | 15-39 mph |
| New snowfall in the last 24 hours: | 0-1 inches |
| Total snow depth: | 85-118 inches |
| Friday | Friday Night | Saturday | |
|---|---|---|---|
| Cloud Cover: | Clouds build mid-day and light showers spread across the region in the afternoon. | Increasing precipitation with lowering snow levels. | Decreasing showers. |
| Temperatures: | 31-49 deg. F. | 20-30 deg. F. | 31-47 deg. F. |
| Wind Direction: | South | Southwest | Southwest |
| Wind Speed: | 8-10 gusts 23-24 | 11-15 gusts 25-31 | 8-10 gusts 23 |
| Snowfall: | 0-1 in. | 1-4 in. | 0-1 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.
