Spring weather has been the recent dominant theme and will continue for a couple of more days with warm daily temperatures and mild nights. A weak spring storm moved through the region Wednesday (4/26) with moderate to strong winds, cooler temperatures, increasing cloud cover (primarily Mammoth north) and light precipitation over the upper elevations forming very isolated and shallow Wind Slabs in the upper elevations primarily on N-E-S-SW aspects. The last significant storm to sweep though the region was Tuesday (4/18/17) with 3” to 12” inches of new snow reported across the forecast area above ~8500’. However, snow levels fluctuated considerably during the storm with many areas receiving rain Monday before turning to snow in the early morning hours on Tuesday. Snow levels rose once again during the day, Tuesday, with rain up to ~ 9,000’ then easing back down to ~8000’ by Tuesday PM. Loose Wet avalanches were prevalent during the storm throughout the mid elevations as the surface snow becoming saturated with water and internal bonds began to dissolve. Moderate to strong SW winds during the storm formed Wind Slabs in exposed locations throughout the mid and upper elevations, primarily above ~ 9000’ on NW-NE-SE aspects with several avalanches observed throughout the forecast region. Mammoth Mountain Ski Patrol reported significant results from avalanche control work on Wednesday morning. Most of these avalanches were triggered in Wind Slabs with small hand charges and ski cutting. Westerly winds continued thru Wednesday and Thursday (4/19-4/20) with snow banners and localized drifting observed from Mammoth south to Rock Creek, forming a new round of Wind Slabs throughout the upper and mid elevations, primarily on N-E-S aspects. Since then, any Wind Slabs that formed have had several days to strengthen. Moderate SW winds in upper elevations Sunday (4/23) formed another round of isolated shallow Wind Slabs in the upper elevations on NW-NE-SE aspects where upwind fetches still had snow available for transport. Since then, there have been several days for the Wind Slabs to strengthen and heal, redirecting the avalanche threat toward typical spring Loose Wet avalanches.
Forecasts for the weekend shows a dramatic change coming as a cut-off Low sets-up over the western US bring unsettled conditions, snow for the high country, and gusty winds. Stay tuned for a possible late season powder treat.