Persistent high pressure and warm daytime temperatures have been edging snowline ever higher in the eastern Sierra. Coverage is thin and patchy below ~9,500’ around Mammoth and higher elsewhere. Early season conditions exist with many obstacles hiding just under the snow surface.
A weak storm system moved through the region Wednesday (12/21) with 1 to 4” of snow reported. Winds began as moderate from the Southwest and then veered to the Northeast as the system left our forecast zone. Sunday the wind increased from the Southwest and some limited snow transport was observed across ridges and in exposed areas. Test slopes near and above treeline showed recent wind slabs to be isolated and increasingly stubborn to trigger. However, temperature gradients in our shallow snowpack have been forming weak, sugary, facet snow in more sheltered locations. The combination of these old wind slabs and persistent weak layers may increase the potential for triggered release on previously wind loaded features near treeline.
As the weather has warmed across the mountains, surface conditions have become moist and sticky below ~10,000’. Treed slopes, rock outcrops, and hazy clouds will all increase surface warming at mid and lower elevations. Below ~9,500’, natural and triggered releases are unlikely due to little or no snow.