Snow vs Rain due to Orographic Lift


If the only impediment to snow is warm air lingering near the surface (or the boundary layer) then orographic lift can cool the air to allow snow to reach the surface. Suppose large scale temperatures are in the upper 30s. If the water temperature, for example, of western Lake Superior is 34 degrees, air just above the water surface will have a similar temperature. When east winds push the air up the hill it cools several degrees to around 32. As a result, snow can reach the ground or accumulate more easily. Lower elevations or areas further inland will experience rain or a mixture of snow and rain.