(CNN) – A big winter storm threatens snow, ice and floods in most of the United States in the coming days.
More than 20 million people are under surveillance and warn of winter storms from New Mexico to North Carolina, where authorities have declared an emergency throughout the state, as in some areas it could snow more than one foot (30 centimeters). ).
"Snow can be beautiful, but it can also be treacherous and I urge the people of North Carolina to take this storm seriously and get ready now," Governor Roy Cooper said in a statement.
As this storm develops, this is what meteorologists expect, where and when:
Arkansas and Western Tennessee
After seeing some precipitation on Friday, the Arkansans will suffer Saturday's winter temperatures as the storm moves east into Tennessee.
shock: Rain, mixed winter, snow in the mountains
North Arkansas will receive up to 6 inches of snow and up to a tenth of an inch of ice.
The southern half of Arkansas will be characterized by precipitation from 4 to 5 inches and sudden flooding. In the center of Arkansas, it will fall to an inch of snow at most. Meanwhile, in the highest areas of the Ozark mountains you will probably see 2 to 6 inches of snow on an ice sheet of up to a quarter of an inch.
Snow totals will be lower in the north-east of Arkansas and in northwestern Tennessee, where you can drop an inch of snow.
East Tennessee, Georgia and Carolinas
when: from Saturday morning to Monday
Inclement weather begins on Saturday, with rains in Georgia and some winter rains in the mountains. It resumes Saturday night, when it is possible that there are snowstorms in the upper Appalachians, with higher accumulations until the beginning of Monday morning in the whole area. Monday's storm will probably move to the sea, but it could also turn and rise on the east coast, which will cause heavy snowfall in major metropolitan areas.
shock: Snow, blizzard, mixed winter and pouring rain
Significant snow, although unsafe, between the mountains of northeastern Georgia and the Carolinas.
Parts of North Carolina could see record snowfall, described by the National Weather Service as "a single event in a generation". The mountains and hills west of Interstate 85, including cities like Winston-Salem, Asheville, Greensboro, and Charlotte, could receive a foot of snow.
However, these forecasts are significantly reduced to 2-3 inches of snow in places like Raleigh and up to an inch in Greenville, South Carolina.
Floods and winter rains can also affect Georgia. The torrential rains between 1 and 3 inches are scheduled for Saturday "at high speed, which increases the threat of flooding," said the National Weather Service.
They could fall from one to two inches of snow in the highest areas of northern Georgia and up to 5 inches on the highest peaks on Sunday evenings until Monday. The possible icy rain and snow could also reach the I-85 corridor, including Atlanta, Monday afternoon.
The total snow to the east of I-85 will depend on a regional meteorological phenomenon called "cold air dyke" or "wedge", when the cold air pushes from the north-east against the Appalachians. The mountain range acts like a dam, keeping the cold air accumulated like a lake. A warmer environment in this scenario would reduce the accumulation of snow. There is another phenomenon called "hot nose" that would allow the hot air to mix above the "wedge" and cause more winter mingling on Saturday night and Sunday night before the snow moves north -ovest of the I – 85.
when: Saturday morning until the afternoon
shock: winter rain
The rain started on Friday in central and northern Texas, moving eastwards, where the fear of sudden flooding increases. It could reach up to 2 inches per hour in coastal cities, including the Houston area, where floods are a concern.
San Antonio and Houston could see flash floods, since the total rainfall could be from 3 to 6 inches, with a maximum of 10 inches in remote areas. From Friday night Austin received 2.95 inches of rain and an area of eastern Texas up to 3.4 inches.
(With information from CNN meteorologists Judson Jones and Monica Garrett)