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Toured into the Middle Fork of the Flathead to look at the effect of overnight rain and warming on snow at low and mid-elevations.
We noted 4 avalanches today, all starting in neighboring SE gullies above Cascadilla Creek. Looking at these from across the canyon, they appeared to be loose wet slides. It rained last night to 4400 feet here and we believed that rain on 7-8 inches of fresh snow was the trigger. The surface below the fresh snow is a 2-3 inch, knife hard melt-freeze crust. Starting points were in steep, confined gullies that we guessed to be 40 feet across on average. Starting elevation of 4500 feet for the three smallest slides.
The largest avalanche was D2 (see photo). This slide was 75 feet wide and 500 feet in length. It started in a confined gully and then fanned out after running through an area of steep brush. The starting elevation is estimated to be 4700 feet. We speculated that this slide could have started as a storm slab and entrained saturated snow from lower elevations. Avalanche debris at the runout had the appearence of wet loose debris.
We also saw evidence of one storm slab that likely ran during yesterday's storm. The crown was 6 inches tall, 150 feet wide and ran 200 feet. This was near a confined gully and started below trees on both sides of the gully. Starting elevation 4400 feet.
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