The avalanche danger is CONSIDERABLE above 5500 feet due to recent strong winds and a bit of new snow. Human triggered avalanches are likely on wind loaded terrain and possible on all other terrain. Weak snow surrounding a variety of crusts from January still poses a problem and the distribution is spotty making it tricky and potentially dangerous. Careful snowpack evaluation, cautious roue-finding, and conservative decision making are essential.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Strong wind speeds will continue today adding more depth to fresh wind slabs that formed yesterday. We observed active wind loading yesterday in the Flathead Range, and other weather stations in the northern and southern Whitefish Ranges confirm this as well. These wind slabs will continue to stress existing weak layers that may release deeper (step down) in the snowpack and propagate wider making for large avalanches. Look for convex pillows of wind drifted snow on the lee sides of ridges. Carefully evaluate all wind loaded terrain and be aware of cross-loaded slopes and gullies as well.
Yesterday's rain and heavy snow (up to 1 inch of liquid) was a decent test our existing weak layers. Buried surface hoar and weak faceted snow exist in all ranges, but you won't find them on all slopes. Weak snow beneath the January 12 rain crust was the failure layer of the fatal avalanche last Saturday. The January 17 rain crust continues to be reactive in some stability tests as well. These weak layers are now 2 to 5 feet deep. There is a lot of variability across the advisory area with this avalanche problem that warrants careful snowpack evaluation and cautious route-finding. Over the past few days stability tests in some locations resulted in no fracture or propagation on deeper layers while in other locations these layers show signs of instability. Given the tricky distribution of these persistent slabs it would be wise to avoid steep, open slopes and convexities on all slopes. The only way to know if these layers are reactive is to dig into the snow and perform stability tests. You are more likely to trigger an avalanche on one of these layers in shallow snowpacks where these layers are closer to the snow surface.
The final report for the 1/23/2016 avalanche fatality in Swede Creek in the Whitefish Range is complete and located here: http://www.flatheadavalanche.org/sites/default/files/20160124_swedecreekavalaccidentreport_final.pdf.
Yesterday, in the Rescue/Skiumah Creek area we found terrible skiing and were able to trigger small, wet loose sluffs on any rollover steeper than 35 degrees. We avoided larger, steep slopes as these wet loose avalanches entrained a fair amount of snow (photo, observation). In stability tests we found mixed results on layers within the top 2 feet and could not get the early January weak snow (below the Jan. 12 rain crust) to fracture in our snow pits. We observed strong winds transporting snow onto leeward slopes.
On Wednesday, Glacier NP rangers were on Apgar Mountain where, in their stability tests, observed fracture and propagation with hard force on the weak snow beneath the Jan. 12 rain crust (observation). Also, on Wednesday at Noisy Basin in the Swan Range, I found mixed results in stability tests ilustrating the variability in our snowpack right now. We found very small wind loaded slopes right off the ridge, and observed rollerballs and pinwheels and mid and lower elevations as the day progressed (observation).
On Tuesday, Mark investigated recent avalanche activity from Sunday in the WMR backcountry. He found the storm snow that was responsible for the recent natural and skier triggered avalanches to have settled out (observation). Also on Tuesday, BNSF avalanche safety reported fracture and propagation with moderate force in their stability tests. Failure layer was decomposing surface hoar and facets that were sitting on top of a melt freeze crust formed during the high pressure event of early January. They also reported a collapse in the snowpack at an upper elevation during their tour (video, observation).
For more information on the recent avalanche fatality in Swede Creek, Whitefish Range (1/23/2016) please view the final report here.
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
In the past 24 hours, rain to 5000-6000 feet across the advisory fell with remote weather stations reporting 0.4 to 1.0 inch of snow water equivalent (SWE). The northern Whitefish Range was the winner with the most precipitation (1 inch of SWE). Snow amounts above the rain level range from 2 to 5 inches. Strong winds accompanied the storm with average speeds of 12-27 mph and gusts to 47 mph. Temperatures decreased overnight. Currently, temperatures above 6000 feet range from 21º-29º F and winds are moving out of the southwest at 5-25 mph with gusts to 41 mph. For today, expect snowfall to begin this afternoon. We could see up to 7-10 inches by tomorrow morning throughout the advisory area. Temperatures will be in the upper 20s to low 30s F. Winds will be out of the southwest at 15-30 mph with gusts to 70 mph.
| 0600 temperature: | 21 to 29 deg. F. |
| Max. temperature in the last 24 hours: | 31 to 25 deg. F. |
| Average wind direction during the last 24 hours: | Southwest |
| Average wind speed during the last 24 hours: | 12-27 mph |
| Maximum wind gust in the last 24 hours: | 32-45 mph |
| New snowfall in the last 24 hours: | 2-4 inches |
| Total snow depth: | 62-87 inches |
| Friday | Friday Night | Saturday | |
|---|---|---|---|
| Cloud Cover: | Brief lull in precipitation until snowfall begins this afternoon. | Snow. | Tapering snow in the morning. |
| Temperatures: | 27 to 37 deg. F. | 20 to 26 deg. F. | 26 to 34 deg. F. |
| Wind Direction: | Southwest | Southwest | Southwest |
| Wind Speed: | 10-20 mph with gusts to 45 mph. | 15-25 mph with gusts to 45 mph. | 10-20 mph with gusts to 40 mph. |
| Snowfall: | 0-1 in. | 5-7 in. | 1-3 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.
