Very unstable air, daylight time

We don’t often see convective showers and clouds pop up in such a grid-like pattern. However, due to very cold air moving in just above the surface (temperatures at 4,000 feet near freezing), yet enough sunshine to warm surface temperatures into the lower 50s, the air is very unstable at low-levels. Nature tends to concentrate the convection (areas of upward motion, clouds, and showers) and the areas of compensating downward motion (areas of clear sky) into a distinct pattern. This is called cellular convection. Here is the balloon data from this morning at NWS BHM.

The red dot indicates the current temperature, and the red line indicates the temperature with height this morning. Notice how quickly the temperature drops with height. Given the cold air, a few reports of small hail have come in, and this may continue.

Also, don’t forget to set your clocks ahead one hour tonight before going to bed. Daylight savings time will start just after 1:59 am, when 2:00 am becomes 3:00 am. Sunsets will be later now by an hour, and with lengthening days, sunset will be after 7:00 pm soon. However, if you don’t move your clocks forward, you will be an hour late tomorrow!

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