Sleet science

By Brandon Evans | Published Saturday, December 7, 2013

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If anybody was praying for sleet over freezing rain from Thursday afternoon into Friday morning, it worked.

In fact, the factors that determine if the earth gets pelted with freezing rain or sleet does start high above the land.

“The temperatures from 3,000 to 6,000 feet determine the type of precipitation falling to he ground,” said Jason McLaughlin, Wise County weather watcher and storm chaser.

What started out as freezing rain early Thursday afternoon quickly turned to sleet and stayed that way throughout the night. It covered the land and roads in a crunchy layer of ice pellets that piled up to 2 inches thick or more between Decatur and Alvord.

What’s pelting Wise County in this winter storm started out as snow about 3 kilometers above the earth’s surface. As it floated down, it passed through a warm layer of the atmosphere about 8,000 feet up. The snow then melted into freezing rain. The thickness of that warm air mass and the temperature below it determines if freezing rain hits the ground or if it turns to sleet.

“If the warm layer is thin, the snow turns to liquid and then into sleet,” McLaughlin said.

The layer was thinner above Wise County and the temperatures were very cold beneath it, already plummeting to 26 degrees by the time the precipitation got strong early Thursday evening.

“More sleet means less potential for power outages as sleet pellets fall to the ground and don’t freeze on power lines,” McLaughlin said.

Oncor Area Manager Sabrina Younger confirmed this Friday morning. She reported only three customers in Wise County (all in the Runaway Bay area) had lost power.

The colder temperatures here in Wise County actually helped because we received more sleet than freezing rain, she said.

The warm air was left behind from the temperatures that hovered in the high 70s on Wednesday afternoon. The cold air mass hit the area early Thursday.

“The cold air comes in and the warm air rises above it,” McLaughlin said.

The cold temperatures, which aren’t expected to rise above freezing until early next week, combined with precipitation to create the perfect winter storm.

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