Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
Voir sur la carte

Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
Open full map
Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Another night of warm temperatures is keeping the avalanche danger elevated. You will find the best riding and safest conditions this morning while the surface is supportable and frozen. As the day progresses and the surface deteriorates, expect wet avalanche problems to develop and the danger to rise. Plan your exit before the snow surface becomes wet and manky. Large cornices continue to weaken and can fail unexpectedly. Stay well back from these impressive features while traveling on ridgelines and minimize recreating on slopes connected to them.

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Warm temperatures overnight and this morning extend our wet avalanche problem for another day.  Natural avalanche activity has ended on sunny slopes but remains a threat on shaded aspects. Triggering a slide on either side of the compass remains a concern, especially on slopes without a supportable crust. Expect the danger to rise through the day as the surface warms and the snow becomes wet and sloppy. Choose lower-angle terrain when you or your machine are sinking more than a couple of inches below the surface. Steep slopes directly above a cliff band, group of trees or other terrain trap can magnify the consequences of getting caught in a small slide.

    (4/3/2021) Recent wet loose slides on a mid-elevation southeast slope.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Large wind features below ridgelines continue to weaken during our extended warm spell. Predicting when and if they will fail is difficult. Until cooler temperatures arrive, it is best to give these impressive drifts a wide berth. It can be nearly impossible to tell where the snow/solid ground line is while traveling along ridgelines, and we recommend remaining further back than you feel necessary. Recreating on slopes connected to cornices should be minimized. 

    (3/29/2021) Large cornices are found throughout our advisory area at upper elevations. Westerly winds are responsible for these features.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–3

    Warming temperatures increase the threat of triggering a weak layer buried 2 to 6 feet below the surface. The force of a van-sized piece of cornice tumbling down the slope could do the trick. You or your snowmachine may also be the trigger that awakens this lurking concern. To minimize your exposure to this problem, choose terrain 35 degrees in steepness or less consistent in slope shape top to bottom. Avoid areas with thin coverage such as a rocky peppered appearance or windswept look.

    (3/16/2021) A hard slab of snow sitting over buried persistent weak layers.

Avalanche Discussion

Ongoing warm conditions are keeping wet loose as our #1 avalanche problem for one more day. A low-pressure system will enter northwest Montana this afternoon bring cooler temperatures, increasing clouds, and light snowfall. This weather change should put a lid on the wet concerns and possibly result in the return to dry avalanche problems tomorrow morning. Due to the overnight changing conditions, we have moved the expiration of today's forecast to 11:00 p.m. instead of the normal 6:00 a.m.

Weather stations at mid and upper elevations continue to report warm overnight temperatures. Some locations are dipping below freezing early this morning, while others remain above freezing. The Tunnel Ridge station has been above freezing for the past four nights, while the station at the summit of the Big Mountain has continuously dropped below 32 F. Despite the balmy conditions, observers found a supportable surface and good corn riding yesterday morning in the southern Whitefish Range and the Flathead Range. The snow surface deteriorated as the day progressed, and they were all wise enough to exit before conditions reached a dangerous state. Both parties did report mushy snow on their egress. Blase found similar conditions in the central Whitefish Range and noted cold snow becoming wet and getting sticky above 6000'. On ski turns, he initiated large rollerballs at this elevation.

You may have noticed that our danger ratings have been around the CONSIDERABLE level for the past week. The combination of new snow and warm temperatures is keeping us on our toes. We hate to cry wolf but have had to rate the danger at this level due to the rising hazard late in the day when the surface becomes wet and mashed potato-like. The actual danger first thing yesterday and this morning are closer to LOW due to a frozen supportable surface. Cooler temperatures this afternoon and overnight should help lock up the surface, and we plan on dropping the danger down a notch at all elevations tomorrow.

Régions couvertes