1. 12 December 1979 Freezing Rain Event
Katherine Donner

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

3. 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

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

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