The avalanche danger is MODERATE above 5000 feet. Mild temperatures overnight combined with continued warming today will weaken the surface snow. Human triggered avalanches are possible today. If temperatures and solar input increase beyond forecasted amounts the hazard could rise to CONSIDERABLE later today. It is important to remember that with wet snow avalanche problems aspect is the answer! As the day progresses and the snow surface becomes increasingly moist move from sunny aspects to a shaded aspect.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
This will be the third consecutive day of temperatures climbing above freezing at all elevations. In areas that were warmed yesterday we will find a thin surface melt freeze crust capping moist snow this morning. This crust should break down quickly with warming temperatures and sunshine. Rollerballs/pinwheels are the first sign of surface instability with wet snow (observation). Loose wet avalanches are a manageable problem! If the skiing and riding conditions start to deteriorate on sunny aspects you need to head to a shaded aspect or call it a day. Even small wet loose slides are difficult to ski or ride out of due to their wet concrete like consistency. Wet loose slides can put a lot of stress (weight) on the snowpack and trigger deeper instabilities.
Recent strong winds created substantial cornice formation throughout our advisory area. Continued warm temperatures and potential solar radiation will weaken these cornices today. This is not the time to ski or ride on or below these features. Cornice falls have the ability to trigger avalanches on any layer of concern in the snowpack (e.g. surface wet loose, wind slabs, persistent slabs). Cornices are referred to as the "bombs of the backcountry" and this is the time to give them a wide berth. Cornice failures were observed in the Apgar Range in southern Glacier Park on Sunday (observation).
Buried surface hoar now about 6 inches to a foot from the surface has produced the most recent activity, but is spotty in distribution. Deeper layers like the weak snow surrounding the the January 17 and January 28 rain crusts are buried 1.5-2.5 feet deep. Recent stability tests suggest that these deeper persistent slabs are gaining strength and are becoming more difficult to trigger. With that said it remains important to perform site specific snowpack evaluation. Dig in the snow and do a stability test, look for locally reactive slabs. Where they are present and there is any question about stability choose conservative terrain to ski or ride in. Avoid areas where you are more likely to affect these layers like in shallow snow and in steep, rocky areas.
Wind Slabs: The wind event our area experienced Friday/Saturday was possibly the most impressive of the season. Moderate to strong winds drifted recent snow and formed wind slabs on multiple aspects at both mid and upper elevations. Recent warm temperatures has initiated the strengthening process within these slabs. However, due to their thickness and wide distribution, lingering wind slabs reactive to a skier or rider remain a concern. In some areas these slabs formed over a recently buried layer of surface hoar (formed 2/3). In these areas instability will linger and avalanches have the potential to propagate far and wide. Look for obvious signs of instability like shooting cracks, whumpfing, and recent avalanche activity. Look for convex pillows of wind drifted snow on the lee sides of ridges and other cross-loaded terrain. Carefully evaluate all wind loaded terrain before traveling on or underneath the slope.
Tuesday: Erich and I traveled to the Marion Lake area of the Flathead Range. We noted moist surface snow on sunny aspects with rollerballs and small point releases occurring throughout the day. Lingering wind slabs from last weekends strong winds were present on leeward slopes. These wind slabs fractured but did not propagate in stability tests. We also were able to identify 3 wind slab avalanches from the weekend (observation).
Monday: Guy and Austin rode into the Mission Mountains (outside our advisory area) and noted evidence of the recent wind event at all elevations. They found 2 layers of surface hoar in a north facing pit and also observed warm conditions and rollerballs/pinwheels at all elevations (observation).
Sunday: Skiers in the Apgar Range in southern Glacier Park noted numerous cornice failures along with possible wet slide debris at lower elevations. Wind slabs varied between non reactive to somewhat reactive. Skiing at lower elevations was "heavy and sloppy" (observation). The Patrol Fund Level 1 avalanche course at WMR in the southern Whitefish Range were able to get failure below the late January crust in compression tests with hard force. They also noted new surface hoar growth overnight (observation).
Saturday: Snowmobilers in the Stahl Peak area in the northern Whitefish Range observed recent natural avalanche activity. They noted wind drifting the snow at all elevations. While side hilling on a road cut they experienced cracking in the windslab 10-20cm deep (observation). We were in the Red Meadow area also in the northern Whitefish Range. Wind was drifting snow and forming wind slabs at all elevations and large cornices were developing along leeward ridgelines. We found weak snow around the January 28 crust that fractured in stability tests without propagation (observation). Snowmobilers in the Lost Johnny area of the northern Swan Range found substantial top loading and cross loading along with a 3 inch thich rain crust 2+feet from the snow surface.
Friday: Skiers in Crystal Creek/Stanton Lake in the Flathead Range intentionally triggered a windslab from the ridgeline. They also noted active windloading forming slabs thicker than 2 feet deep (observation). Skiers on Snowshed Mountain also in the Flathead Range observed light winds with minimal drifting due to scoured windward slopes. They did note evidence of recent wind loading as knee deep soft slabs had formed on leeward slopes. Stability tests produced fractures with hard force on weak snow surrounding crusts 1.5-2 feet deep. They did not observe recently formed buried surface hoar in this location (observation). Snowmobilers in the 6-Mile area in the Swan Range noted substantial recent windloading. They did not see recent avalanche activity, but did experience other obvious signs of instability like cracking and collapsing (whumphing).
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
Overnight, clearing skies and strong inversions have allowed temperatures at valley floor locations to cool below freezing with mid and upper elevations remaining relatively mild. Today expect another warm day with mid and upper elevation locations remaining warmer than valley floors. There will be a layer of high clouds mixed in with the sunshine which will determine just how warm we get. Yesterday, the valley floor Fielding weather station (4641 feet) in southern Glacier Park topped out at a balmy 53° F! Today expect temperatures to climb above freezing at all elevations with possible readings from the mid 30°s to mid 40°s F at upper elevations. Currently temperatures above 6000 feet range from the low to mid 30°s F with light winds and clear skies.
| 0600 temperature: | 31-41 deg. F. |
| Max. temperature in the last 24 hours: | 39-45 deg. F. |
| Average wind direction during the last 24 hours: | SW |
| Average wind speed during the last 24 hours: | 5-15 mph |
| Maximum wind gust in the last 24 hours: | 10-20 mph |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 61-92 inches |
| Wednesday | Wednesday Night | Thursday | |
|---|---|---|---|
| Cloud Cover: | Warm. | Clouds moving in. | Not quite as warm. |
| Temperatures: | 36-49 deg. F. | 26-32 deg. F. | 34-42 deg. F. |
| Wind Direction: | W-SW | SW | SW |
| Wind Speed: | 6-7 gusts 17 | 7 gusts 16-20 | 5-10 gusts 16- 25 |
| 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.
