Not only did Sunday’s winter storm deliver up to six inches of snow in parts of Williamson County — it also brought rare thundersnow to the Austin metro area.
What is thundersnow?
In short, thundersnow is a thunderstorm that occurs when temperatures are cold enough for precipitation to fall as snow instead of rain.
Although thunderstorms are less common in the winter because cold air has less instability and energy, thundersnow can happen when strong instability and abundant moisture are in place above the surface.
This was the case with our weather setup on the boundary of the rain/snow line on Sunday. Temperatures in the pure snow region of the storm in the western Hill Country were too cold and moisture values too low to produce lightning and thunder. But on the rain/snow transition line in the Austin area, moisture values were higher and temperatures were warmer. That combined with the tremendous upward forcing from the passing low pressure system were enough to produce several lightning strikes as snow fell over the city.