Spring had been in full swing in the Sierra for the past week with high pressure, sunny skies, and seasonable to above seasonable temperatures interrupted by the occasional fast moving shortwave passing through the region and depositing a few inches of snow before moving east. The snowpack has mostly consolidated and is primarily characterized by Melt-Freeze crusts separated by rounds or decomposing grains closer to the snow surface with isolated pockets of cold winter like snow on Northerly to Northeasterly aspects in the upper elevations . Thursday (4/6/17) winter made a late season reappearance with the arrival of another Atmospheric River event forecasted to impact the Sierras thru Saturday. Thursday, snow levels initially in the Central Sierra hovered around 9000 feet in Mono County with precipitation picking up in the late afternoon as strong convective showers moved through the region. Overnight, heavy precipitation began impacting the Sierra with a Winter Storm Warning issued for the Sierra tonight through Saturday with storm totals of 2’ to 4’ of new snow forecasted. The sub-tropical nature of the system will produce heavy dense snow, which hasn’t had sufficient time to bond and sinter to the old snow surface and possible density changes within the new snow will likely form sensitive Storm Slabs at all elevations. As a result, the risk of Storm Slab avalanches has increased substantially and will remain a threat for the forecast period. Additionally, the current storm system moved into the region Thursday night with strong to extreme Southwesterly winds (gusts over 100 mph along the Crest) forming widespread sensitive Wind Slabs on NW-N-NE-E-SE aspects, primarily mid to upper elevations. These may be encountered below ridgelines and near and adjacent to terrain features that promote crossloading. Localized channeling and turbulent winds can produce Wind Slabs further downslope than anticipated and on unusual aspects, in relatively sheltered terrain, and potentially extending well into the mid elevations (8000’-10000’). Travel in avalanche terrain not recommended.