12 December 1979 Freezing Rain Event Katherine Donner

Previous day’s temperatures in mid 60s. Strong cold front passes At 12Z December 12, frontal boundary from southern Texas through Shreveport, LA

Exit region of 500mb trough over Oklahoma 500mb trough deepens Exit region of 500mb trough over Oklahoma 12Z 11 Dec 1979 12Z 12 Dec 1979

Sounding: Sfc temp -1.7°C, sfc dwpt -7.7°C Shallow layer below freezing (sfc-900mb) Deep layer above freezing from 900-700mb Saturated from 700-470mb SW flow at 500mb, winds ~50kts

Sounding: Veering wind profile indicates WAA Frozen precipitation forms at 500mb ~-10°C Unsaturated region from 850-700mb Ice particles becoming liquid droplets Liquid droplets eventually saturate air again before falling through the shallow freezing layer to the sfc Saturated from 930-850mb Air at the surface will eventually become saturated as freezing rain begins to fall.