Increased black ice risk as temps will drop after precipitation this week

Rain or snow will sweep across Korea on Thursday, and forecasters warned that temperatures could drop by about 10 degrees Celsius (18 degrees Fahrenheit) after the precipitation clears, raising the risk of black ice.

Shoppers wearing winter gear shop at the Dokkaebi Market in Jeonju, North Jeolla on Dec. 3. [NEWS1]

Rain or snow will sweep across Korea on Thursday, and forecasters warned that temperatures could drop by about 10 degrees Celsius (18 degrees Fahrenheit) after the precipitation clears, raising the risk of black ice.

The Korea Meteorological Administration (KMA) said that rain would start early Thursday in Seoul, Incheon, Gyeonggi and Gangwon, as well as in the Jeolla region and on Jeju Island. The KMA added that the system would spread to most of the country by late morning as a low-pressure trough moves through.

Colder areas will likely see snow, including parts of eastern Gyeonggi, Gangwon and the northeastern mountains of North Gyeongsang.

Most of the rain will stop before the afternoon, but snow and rain may continue through Friday in eastern regions such as Gangwon.

Precipitation is expected to be light, between 5 to 10 millimeters (0.2 to 0.4 inches). However, mountainous regions and the east coast of Gangwon could see 3 to 8 centimeters of snow, with some areas possibly receiving more than 10 centimeters.

After the rain, temperatures will plunge below zero degrees Celsius.

In Seoul, the morning low on Thursday will be 6 degrees Celsius, warmer than average for this time of year. But by Friday morning, the temperature is expected to fall to minus 4 degrees Celsius.

“Freezing rain or snow could create icy road conditions, especially in areas where ground temperatures remain low,” the KMA said. “Drivers should reduce speed and exercise caution, and pedestrians should also be careful.”

Drivers should remain alert for black ice, a winter hazard that is nearly invisible on the road and can make vehicles difficult to control, increasing the risk of chain-reaction crashes and severe accidents.

Tourists enjoy falling snow in central Seoul on Dec. 4. [NEWS1]

A team led by Lee Chae-yeon, a professor at the Atmospheric Environment Research Center at Hankuk University of Foreign Studies, found that black ice typically forms under four conditions: when temperatures drop and humidity exceeds 80 percent, when light rain is followed by a sharp temperature drop, when supercooled rain hits cold surfaces and when previously melted snow refreezes.

Topography also plays a key role. Areas near rivers provide moisture that contributes to black ice formation. Roads near tunnels and bridges are especially vulnerable.

“Tunnels are often surrounded by mountains, which trap cold air and keep the road shaded, making them consistently prone to black ice,” Lee said. “Bridges are not in contact with the ground, so they cool quickly and create conditions where black ice, once formed, tends to persist."

Snow or rain is also expected over the weekend. On roads prone to black ice, authorities advise drivers to slow down and avoid sudden braking or sharp turns to reduce the risk of accidents.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom. BY CHON KWON-PIL [paik.jihwan@joongang.co.kr]