The temperature stayed below 32ºF from Sunday evening until about lunchtime Tuesday (roughly 38-42 hours for most of North Alabama and Southern Tennessee); the majority of that time spent in the twenties means some unique ice formations like this ‘ice spike’ from Steve McDaniel’s deck in Madison!
The ‘spike’ shape is the most common, but they have been known to form vase-like shapes, candle shapes, and inverted pyramid shapes.
Ice spikes often form in bird baths or dog bowls like those above because the shape of the basin favors their formation. The following partial explanation and diagram are taken from “Ice Spike Formation Induced by Dendritic Ice Sheets” by Miles Chen:
In other words, ice crystals don’t create a smooth, solid block; there are cracks and crevices that allow water from below to seep upward. That makes it possible for more water to move upward and freeze as it rises above the rest of the ice. These things are just as common with ice trays in freezers as they are in backyard birdbaths in cold weather!
We also saw a few frozen fountains on Tuesday like Wilson Park in Florence:
…and this one at Depot Park in Cullman. The sun worked on the southern side of it, but the northern side stayed solid ice all day long.
Tuesday afternoon, as temperatures rose from "You've got to be kidding!" to a balmy "Give me a break," sunshine coming from the south turned the Depot Park fountain from a wedding cake into a caped crusader. (W.C. Mann for The Cullman Tribune) @WVTM13 @HarmonyWVTM13 @simpsonwhnt pic.twitter.com/TcGyIqqOhP
— The Cullman Tribune (@CullmanTribune) January 21, 2020
And this one in Hanceville: