They find a mysterious object after storms in Florida 0:50
(CNN) --
An atmospheric fluvial event that will bring large amounts of moisture to the western US this weekend will gradually move across the country and create hazardous weather affecting millions of people.
The strong storm will begin in the west with heavy snow, gusty winds, and coastal flooding, and then move east, threatening possible blizzards in the Midwest and tornadoes in the South.
“Extreme snowfall is likely in the Sierra and in northern California,” the Weather Prediction Center said Saturday.
He added that "prolific snowfall rates of almost 8 centimeters per hour are expected in the Sierra Nevada, accumulating to more than 1.5 meters through this Sunday in some areas."
More than a dozen western states are under winter weather watches this weekend as the powerful storm system moves through the region.
Snow can accumulate in the Sierras, in the Rockies, and in the Cascades.
The heavy rains will also be important along the west coast, particularly in California, where there are concerns about possible flooding that could occur until Sunday.
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More than 10 million people in the US are under winter storm alert
An atmospheric river is a column of moisture that flows from the Pacific Ocean.
Similar to a fire hose, it shoots moisture into an area for an extended period of time, resulting in very heavy rain or snow.
Most coastal communities will pick up 1-3 inches of rain over the weekend, with some areas of northern and central California could receive 3-5 inches of rain total.
Coastal erosion and flooded roads are major concerns.
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“Heavy rains can cause isolated runoff problems, especially in recently affected areas,” the Climate Prediction Center said.
Hurricane-force wind gusts of 80 to 100 mph are also possible across mountain ranges this Saturday, bringing blizzards of snow leading to near-zero visibility and making travel conditions difficult or outright impossible. .
21 tornadoes and 2-inch hail among weather threats in the southern US.
“Gusty winds and heavy snow could bring down tree limbs,” the National Weather Service office in Sacramento, California said, which could lead to “difficult conditions.”
And the western US will not be the only area affected by the storm.
"As the system moves toward the plains early next week, a spring storm system will develop," said CNN meteorologist Chad Myers.
“There will be severe weather in warm air across the South and a major snow and ice event will occur over the western Great Lakes and northern Plains.”
Possible blizzard conditions for the Plains and Midwest
For the Northern and Midwestern Plains, the threat of blizzard conditions is increasing as significant snow, high winds, ice and freezing rain are possible early next week from Colorado to Wisconsin.
“A winter storm is expected to impact the Northern Plains Monday through Thursday night,” the Bismarck, North Dakota, office of the National Weather Service reported.
"Difficult travel conditions are expected this Monday night through this Wednesday night due to heavy snowfall, reduced visibility and drifting snow."
Heavy snow and wind will be the main concerns, but freezing rain and ice are also possible.
If the winds are at least 35 mph and visibility is less than 1,300 feet for at least three hours, it could cause a region-wide blizzard.
File photo of a snowfall in Buffalo in late April.
Widespread snow accumulations in the Northern Plains and Midwest will be 4 to 8 inches, with some locations could accumulate 12 inches through Friday of next week.
"While some uncertainty remains, there are certainties that high winds and significant snowfall will produce hazardous impacts across much of the Northern/Central Plains and upper Midwest," the forecast center said.
Slippery roads and near-zero visibility conditions will make travel very difficult, if not impossible, in some of these areas.
Power outages will also be possible due to very high winds.
Severe storms for the south next week
The threat of severe storms is also increasing in the southern Plains and Gulf Coast region, with possible tornadoes, large hail, and destructive winds.
"While December tornadoes are rare compared to what happens in the spring, they are often more likely in parts of the Southeast and the lower Mississippi Valley, where there may be a secondary peak in the fall and winter." Matthew Elliott, a meteorologist with the Storm Prediction Center, told CNN.
The severe storm potential begins this Monday night in Oklahoma and north Texas, and will gradually spread to Arkansas, Louisiana and Mississippi on Tuesday.
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Severe storms are likely to continue Tuesday night throughout the Gulf Coast region.
Nighttime tornadoes are more dangerous because many people are asleep and don't know they need to get to a safe place.
Heavy snowfall in New York leaves communities under a layer of snow of almost two meters
While the greatest tornado threat persists during the day, there is still a chance for a few rotating storms during the evening hours.
By this Wednesday, there is a greater threat to an area from New Orleans to Panama City, Florida.
"Details about the areas at highest risk for tornadoes will become clearer as the event approaches and the trends we see today on a smaller scale become more apparent," Elliott explained.
Because the forecast can change, it is important to pay attention to events in the coming days.
CNN Meteorologist Haley Brink contributed to this story.
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