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Thundersnow

Duluth, MN

November 13, 2010

Event summary from personal observation

Snow started around or shortly after 5 AM November 13, but light and intermittent at times until 10 AM. Temperatures, initially in the upper 30s, limited accumulation until the snow became heavier and temperatures dropped after 11 AM. Moderate to heavy snow fell through the afternoon and early evening to about 8 PM. A convective burst of intense snow occurred from 3:20 to 3:45 PM. Heard thunder at 3:35 PM, 3:37 PM, and 3:40 PM. Snow accumulated 2 inches from 3 PM to 4 PM. Snow continued at a much lighter rate for the rest of the night to around 10 AM the next day.

Highly variable snow accumulations

Precipitation in the morning and early afternoon fell as mostly snow or all snow along and inland of the ridge crest but fell as rain or snow mixed with rain at the bottom of the hill. Heavier snow in the afternoon caused a changeover from rain to snow in the lower elevations. The melting snow helped to cool the air that was being influenced by the warmer water of the lake. As the changeover occurred, plumes of white snow could be seen spiking down into the gray-colored rain with the spikes of snow getting lower and lower in elevation. Around 10 inches fell on top of the hill with only a few inches near the bottom. The National Weather Service in Duluth measured 10.9 inches several miles inland from the ridgeline. Personal measurement was 9.1 inches just over the ridge. The weight of the sticky wet snow broke a few tree limbs.

Radar images

Radar image at time of thundersnow from the National Centers for Environmental Information's data access page

3:35 PM CST November 13, 2010

Surface and upper level (500 mb) maps showing evolution of the storm

Atmospheric charts from the National Weather Service Storm Prediction Center archive

Surface analysis - 6 AM CST November 13, 2010


Surface analysis - 6 PM CST November 13, 2010


500 mb analysis 6 AM CST November 13, 2010


500 mb analysis 6 PM CST November 13, 2010

Very sticky snow