Loose Wet activity that was expected yesterday was not as pervasive as anticipated. Cloud cover moved in quicker and thicker than expected, which helped keep the surface snow cool, limiting Loose Wet activity to steep rocky terrain. Today’s (Monday) forecast is calling for Partly Cloudy to Sunny skies and mild temperatures below 10,000’, which will increase the likelihood of generally small Loose Wet releases to on solar aspects (SE-S-SW), primarily tree line and below, as temperatures begin to rebound.
The latest storm to traverse through the region brought anywhere from 9” to 20”+ (SWE 1” + for many locations) of new snow Thursday/Friday with the greatest amounts of new snow concentrated around the Mammoth/June area, lesser amounts north and south. Moderate to strong W-SW winds in the upper elevations throughout the storm formed Wind Slabs in the mid to upper elevations, primarily on NW-N-NE-E-N-SE aspects, which have begun to strengthen and sinter to the underlying snowpack. Winds have eased over the past two days, allowing recently formed Wind Slabs time to bond and strengthen, becoming less sensitive to human triggered release. Lingering sensitive Wind Slabs may still be lurking in the upper elevations but becoming increasingly isolated and stubborn.
The previous Storm Slab problem noted Thursday has generally healed. Sheltered locations from near tree line and below, the recent snowfalls are bonding well to the underlying snowpack.
The graupel layer previously reported (3/14) in the June and Crestview area is still present but is showing signs of strengthening with hand shears now moderate. The graupel layer can be found primarily below 10,000’, ~25cm to ~70+cm (~10” to 25”) deep.
Loose Dry sluffs may be encountered in isolated steep terrain as the surface snow begins to facet near and below tree line in steep sheltered locations. While these slides are not a concern for burial, they can sweep a rider into potential hazardous terrain or obstacles.
The lingering persistent weak facets from early season continues to linger but are showing signs of sintering and rounding, with some shallow areas becoming wet and refreezing. The facets are strengthening and becoming more deeply buried in many locations, making it more difficult to trigger. The most recent storm (3/16), despite adding the stress of an inch or more of water weight to the snowpack, wasn’t enough to tip the balance and cause this layer to become more reactive, at least based on observations. As the facet layer slowly recedes into the snowpack depths (Mammoth / June) area and the facets continue to round and sinter, the concern is becoming more limited and isolated. However, the storm forecasted for Thursday has a strong AR signiture and is forecasted to drop 3 to 4" of water over the Sierras. This may be enough weight to cause this layer to become stressed and reactive.