Fog Formation Linked to Low-Level Moisture in River Valleys
ALTON - Residents in the Metro East region of Illinois experienced varying visibility conditions due to fog that developed overnight, primarily affecting areas within five to ten miles of the Mississippi River. National Weather Service in St. Louis Meteorologist Jayson Gosselin noted that the clearing of clouds from west to east allowed for low-level moisture to linger, contributing to the formation of fog in specific areas. In Alton, near the Mississippi River, the fog was very difficult for motorists. The fog was not uniformly widespread, but found primarily in river valleys, the meteorologist said. For instance, southeastern St. Clair County reported minimal fog presence. Gosselin explained that dew point measurements, which indicate the amount of water vapor in the air, played a significant role in this phenomenon. "When the temperature hits the dew point, saturation occurs, leading to cloud formation. Fog is essentially a cloud that forms just above the surface," he said. Visibility
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