Avalanche Forecast

Fair - Forecast snowfall amounts are uncertain on Tuesday

A Pacific frontal system should move on to the coast this afternoon or evening. The front is forecast to be fast moving and should affect the interior ranges overnight Monday. Forecast snowfall amounts are 5-10 cm overnight combined with strong southerly winds. The wind is expected to shift a bit to the southwest and continue to be strong during the day on Tuesday as another 5-10 cm is expected to accumulate. Unsettled weather is forecast for the interior mountains on Wednesday as the fast moving system should have moved on to the East. On Thursday a weak low pressure system is expected to move up from south of the U.S. border spreading light to moderate precipitation mostly to the southern regions of the interior.

Natural avalanches up to size 3.0 were reported from Sunday during periods of strong solar radiation. A couple of natural cornice falls released avalanches up to size 3.0, and there were a few reports of large cornice falls that did not release any slab from the slope below. Reports of avalanches failing down to the mid-February persistent weak layer are getting less frequent. The PWL is becoming a low probability, high consequence avalanche problem.

Sunny periods on Sunday developed a sun-crust on southerly aspects up well into the alpine. The recent storm snow is reported to be bonding well to the old surface. There is a persistent weak layer (PWL) of buried surface hoar from mid-february that is buried between 100-200 cm that is the main concern. This PWL shears with a fracture character that promotes wide propagations that result in very large avalanches. Reports of avalanches on this layer are becoming less frequent. Forecast strong winds and new snow may build new windslabs in the alpine and at treeline.