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Winter Weather: The science behind different precipitation types

The depth of warm air aloft will change the type of winter precipitation we see.
The depth of warm air aloft will change the type of winter precipitation we see.(WOWT)
Published: Nov. 11, 2020 at 4:33 PM CST
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OMAHA, Neb. (WOWT) - Rain, freezing rain, sleet and snow… From Monday into Tuesday morning, portions of the WOWT viewing area experienced all four of these precipitation types.

Freezing rain fell along a corridor just northwest of the Omaha Metro, icing over trees and causing power outages. Farther into northeastern Nebraska, heavy snow piled up. In Omaha, most of the system fell as rain.

The type of winter precipitation we experience has to do with so much more than the air temperature at the surface. Just because a weather station is measuring a temperature of 32°, does NOT necessarily mean snow will be falling. We have to look at the entire temperature profile through the atmosphere!

This is why weather balloons come in handy. National Weather Service offices across the country send up weather balloons twice a day, every day, to give us a better look at weather conditions throughout the atmosphere.

Weather balloons are important instruments for weather forecasting.
Weather balloons are important instruments for weather forecasting.(National Weather Service)

Below is the sounding (weather balloon data) from the National Weather Service Office in Valley from Monday night. If you’re not used to reading something like this, it likely looks like a bunch of squiggles. For more on how to read a Skew-T diagram (seen below), click here: https://weathertogether.net/weather-101/how-to-read-skew-t-charts/

Warm air aloft kept the precip-type as rain or freezing rain, depending on surface temperatures
Warm air aloft kept the precip-type as rain or freezing rain, depending on surface temperatures(wowt)

On this particular sounding, I can tell there was a wedge of warm air above the surface. This allowed precipitation to fall as rain in Omaha. Temperatures (at the surface) in the Metro were hovering in the mid-30s.

To the northwest, where temperatures cooled off quicker, rain froze on contact with trees and power lines Monday night. Surface temperatures were in the upper-20s and lower-30s in these spots.

Throughout the event, the upper-air cooled off… transitioning rain and freezing rain into sleet and eventually snow. As you can tell from the soundings Tuesday morning and Tuesday evening, the wedge of warm air became less noticeable, and then disappeared all together.

Precipitation changed over from rain/freezing rain to sleet in spots Tuesday morning
Precipitation changed over from rain/freezing rain to sleet in spots Tuesday morning(wowt)
At the tail end of the system, precip-type was all snow as the atmosphere cooled below-freezing.
At the tail end of the system, precip-type was all snow as the atmosphere cooled below-freezing.(wowt)

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