A shelf cloud is a low, horizontal wedge-shaped cloud, associated with a thunderstorm gust front (or occasionally with a cold front, even in the absence of thunderstorms). A rising cloud motion often can be seen in the leading part of the shelf cloud, while the underside often appears turbulent, boiling, and wind-torn.
Most false tornado and false funnel cloud reports are associated with shelf clouds. Shelf clouds are low-hanging, horizontal cloud features attached to the front side of lines of storms or even a single storm. Usually there isn't any persistent rotation on a vertical axis within shelf clouds or within individual cloud fragments that extend downward from the shelf cloud, therefore they are just another scary-looking cloud.
Shelf clouds often resemble snow plows, big waves or tsunamis and can be very scary-looking since they are usually low-hanging. Sometimes they may found only a couple hundred feet above the ground. There are two other phenomena that might resemble tornadoes or funnel clouds but are not 1) dark rain shafts or narrow columns of heavy rain, and 2) the white color of a hail shaft, a column of hail extending from the ground to the cloud base, may generate a light-dark contrast with surrounding rain, resulting in what might appear to be a funnel cloud or a tornado to the untrained eye.
The coldest air of the season so far and some snow will pour into the northwestern United States by early next week.
Arctic air settling over Germany may prompt children to leave their shoes for St. Nicholas indoors instead of outside before going to bed on Monday night.
A deadly wildfire exploded in Tennessee this week, charring a popular resort town and causing devastating damage.
On the heels of Cyclone Nada, a new and more significant tropical cyclone threatens to take aim at India next week.
Dashing hopes for Christmas Day snowmen and white rolling hills, forecasters predict Britain's weather pattern will leave more to be desired on Dec. 25.
Rounds of heavy rain will heighten the risk for flash flooding across portions of the southern United States through the weekend.
As colder air sweeps into the northeastern United States, temperatures will settle to seasonable levels, and lake-effect snow will erupt into Saturday night.
Thousands of firefighters from across the country answered the call to help save the South, not just on the front lines but also back in camps supporting those out among the flames.
A tranquil beginning to December will be replaced by unsettled weather ahead of the holidays.