(WGHP) – The first weekend in June was off to a beautiful start with sunshine and temperatures in the mid to upper 80s across the Triad.
However, by Saturday afternoon and evening storms began popping up across the area. At least five severe thunderstorm warnings were issued by the National Weather Service and reports of downed trees, powerlines and small hail came pouring into the FOX8 newsroom.
Let’s dive into why storms moved in Saturday evening and why temperatures were cooler than forecast on Sunday.
Cold front sparked storms Saturday evening
Saturday in the Piedmont Triad was the warmest day of 2023 so far with a high temperature of 87 degrees recorded at Piedmont Triad International Airport. When temperatures get that warm and humidity is high, meaning there’s moisture in the atmosphere, combined with a cold front moving in from the north, storms are able to pop off as the cold air moves in behind the front.
The clashing of the warm, moist air ahead of the front mixed with the cold air behind the front led to severe thunderstorms across the Triad on Saturday evening.
Saturday’s storms were also moving in from a direction we don’t always see. In the Triad, typical storm movement in west to east as a cold front approaches through the NC mountains before reaching central North Carolina. However, storms moved through the Triad from a north or northeast to southwest direction on Saturday.
The reason had to do with the placement of a high-pressure system behind the cold front as well as the direction the front was moving from. The cold front moved from north to south into the Tar Heel State instead of the typical west-to-east movement. This is known as a “backdoor cold front”.
What is a backdoor cold front?
The upper-level winds in the atmosphere typically mean that cold fronts in North Carolina move from west to east. However, this is not the case with a backdoor cold front.
A backdoor cold front means that the cold front is basically moving in an opposite direction than normal, so east to west or northeast to southwest.
According to the American Meteorological Society, they form when a high-pressure system pushes cold air south and west. In the Northeast and mid-Atlantic, cooler, wetter air moves in off the Atlantic and replaces the warm, dry air over the land.
Since backdoor cold fronts bring cool, damp air into the Mid-Atlantic, it keeps the area cool and cloudy.
The University of Illinois at Urbana-Champaign states that backdoor cold fronts are more common in the Northeast however, the front can extend into the mid-Atlantic impacting other states like Maryland, Virginia and the Carolinas.
Backdoor cold fronts bring a shallow layer of cooler, marine air. Since the cooler air typically only reaches a few thousand feet above Earth’s surface, the front has a hard time lifting over the Appalachian mountains.
When the cold air gets stuck at the surface and trapped against the mountain range, this is called cold air damming.
According to the National Weather Service, cold air damming occurs because cold air is dense and cannot rise unless it’s heated so it gets trapped on the eastern side of a mountain range. This results in cooler temperatures and cloudy skies.
Sunday in the Piedmont Triad was an example of a backdoor cold front followed by a brief cold air damming event. The cool, moist air that moved in behind the backdoor cold front led to cloudy skies Sunday and the cooler, dense air was unable to rise beyond the mountains.
Therefore, Sunday was left nearly 20 degrees cooler than Saturday with cloudy skies throughout the day.