(CNN) — More than 60 million people are under winter weather alerts prompted by two major storm systems taking shape this week.
The first will dump significant snow from the Central Plains to the Mid-Atlantic Coast through Tuesday night. The deepest snow will pile up across Iowa. Some of the snow will be very heavy, with rates of up to 2 inches an hour, says the Weather Prediction Center.
“If these snow totals materialize, they would be very rare for Iowa,” the National Weather Service in Des Moines wrote.
“On average, single daily snowfalls of a foot or more only historically occur every 15 to 20 years.”
If a foot of snow falls in Des Moines in a day, it will only be the 10th time a foot or more has fallen since 1884. The last time they saw this much snow in a day was in 2004.
“Snow in the Midwest is not rare,” said CNN meteorologist Chad Myers who spent years forecasting snow in the Plains. What makes this system rare is how much is expected to fall in one day.
Des Moines is much more likely to see over a foot of snow build over two or three days.
“This storm with such a wide area of 12 to 18 inches may stretch road-clearing assets thin,” said Myers. “Be ready to be stuck a few days.”
Outside of Iowa, snow over 4 inches is expected from Kansas to Michigan.
It isn’t just snow that may cause problems. Ice could accumulate just south of the snow stretching from Kansas to New Jersey. Up to a tenth of an inch of ice with localized spots up to a quarter inch could form.
“Travel may quickly become hazardous across portions of this region,” according to the prediction center.
Rain will fall across the Southeast, where daily temperatures will surge above average. Severe storms may develop across the Mississippi River Valley, including eastern Arkansas and western Tennessee.
West Coast atmospheric river could bring record snow
Another system is forecast to push through the West Coast region Tuesday into Wednesday.
“The midweek system aligning with an atmospheric moisture surge has the potential to dump an extreme amount of precipitation, potentially flirting with snowfall duration records, in portions of southern California and the western Great Basin,” said Jenn Varian, a weather service meteorologist in Las Vegas.
The Sierra Nevada is anticipated to take the brunt of the moisture with this system, said Varian, but additional spillover could be possible depending on storm heights.
The mountain crests could see anywhere from 60 to 100 inches of snow Tuesday evening through Friday morning.
Northwestern California, as of Monday, looks likely to see the most rainfall. “Moisture plumes with AR (atmospheric river) events are always tricky and may not know more details until the event begins to unfold,” said the San Francisco National Weather Service office.
Atmospheric rivers are long, narrow regions in the atmosphere — like rivers in the sky — that transport water vapor, according to the National Oceanic and Atmospheric Administration
Forecast rain totals from Tuesday through Thursday night range from 2.5 to 4.5 inches in the lower elevation locations. In comparison, the hills could see 6 to 8 inches, maybe even isolated amounts of 10 to 13 inches of rainfall.
“Heavy rainfall may lead to debris flows and flash flooding in and near recent burn areas,” the National Weather Service in San Francisco warned. Those near these areas need to be ready in case evacuation is necessary.
Ahead of this midweek system, much of the region will deal with stiff winds. High-wind warnings and advisories are posted from Los Angeles to Phoenix.
Tuesday into Wednesday, winds could gust as high as 60 mph across portions of California.
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