A major storm system that could dump several feet of snow in the west and bring blizzard conditions to the northern plains approached the west coast on Friday evening, the start of a slow journey across the country during all week and the following weekend, forecasters said. Saturday.
The storm system moved across the North Pacific on Friday and will enter California over the weekend, forecasters from the National Weather Service’s Weather Prediction Center said Saturday in a short-range forecast. The storm will continue to bring mountain snow and coastal rain to the west.
Winter precipitation will extend from the Great Lakes region to the northeast on Sunday. The South could see heavy rain and thunderstorms.
Computer modeling has given forecasters confidence to predict the kinds of risks that will occur early in the week as the storm sweeps through the central United States. Here’s what forecasters think is likely to happen.
Extreme winter impacts are very likely in the West this weekend.
The storm system began moving onshore Friday evening, bringing strong winds to the California coast. Heavy rains in lower elevations that can lead to flooding.
In the mountains, however, this moisture will fall as heavy snow.
“Impacts will be widespread from north to south with numerous winter weather advisories in effect,” the Weather Prediction Center said Saturday morning, adding that “the heaviest snowfall is expected for the Sierra Nevada” with several expected feet.
Forecasters are predicting “extreme impacts” – the most severe warning on the weather service’s winter storm severity scale – across the Sierra Nevada this weekend.
Learn more about extreme weather conditions
As this low-pressure system moves across land, it will tap into an atmospheric river – an area of moisture that crosses the sky like a river at one level of the atmosphere near where the planets are flying. planes. The combination will allow total snowfall to reach one to three feet over much of the higher terrain.
More than five feet of snow is expected in parts of the Sierra Nevada, the Prediction Center forecasters wrote.
At least 20,000 customers served by the Sacramento Municipal District were without power Saturday morning due to the stormy Weather report.
Forecasters believe blizzard conditions will occur over the plains.
“We are increasingly confident that we will be dealing with a fairly large blizzard in the Northern Plains next week,” said Greg Carbin, chief of forecast operations for the Weather Prediction Center.
The system will move out of the Rocky Mountains and begin to strengthen, increasing the chance of heavy snow and very strong winds through Wednesday across the Northern Plains. The Winter Blast is possible from Colorado, including Denver, and northeast across the Northern Plains. Across the Dakotas, at least one foot is likely, Mr. Carbin said.
“The potential exists there for really impressive amounts,” he added, as he expects this storm system to most likely slow down.
Snow in the mountains of the Central Rockies and Arizona could reach a foot Sunday evening.
Severe storms, possibly accompanied by tornadoes, are expected in parts of the south.
It seems very likely that severe storms, possibly capable of producing tornadoes, will form Tuesday in an area of eastern Texas across Arkansas, Louisiana and much of Mississippi, said Bill Bunting, chief of forecasting operations at the Storm Prediction Center.
“Most severe fall and winter weather events typically have several characteristics in common, including a low pressure system near or north of the area of concern, increasingly wetter airflow from the Gulf of Mexico north before the event and a cold front moving east towards the region,” Bunting explained.
“A similar pattern is expected early next week,” he said, “which gives us confidence in the potential for a targeted area of severe thunderstorms and possibly tornadoes.”
Tornadoes are not uncommon at this time of year, but they are less likely than in spring and early summer.
“We average about four days in December a year with at least one EF1” – rated on a tornado damage scale of 0 to 5 – “or stronger tornado,” said Harold Brooks, lead scientist at the National Severe Storms Laboratory, part of the National Oceanic and Atmospheric Administration. “There are about 100 days with an EF1 or stronger tornado during the year.”
Severe winter storms like those forecast for next week can be more dangerous than those that form during peak severe weather season in May and June.
“Because the days are shorter,” Mr. Brooks explained, “they are more likely to occur after dark,” he said of the storms. This “makes them more dangerous” because people in danger cannot spot them as they approach, he said.
“They are also more likely to occur in the South-Central and Southeast United States, which have a higher rural population density than the Plains and have a higher fraction of prefab housing and poverty,” he added. “So the impacts can be bigger.”
Snow is expected Sunday for southern New England, the Northeast Interior and central Appalachia, forecasters said Saturday.
“Moderate snow totals between 3 and 4 inches are possible inland for higher places like the Berkshires and Catskills, and 1 to 2 inches are possible farther south in central Pennsylvania,” according to the forecasts.
Severe weather is expected to last through Tuesday evening and Wednesday. Later in the week, predictions of what the storm might bring to the east are less certain. A coastal low is very likely but unlikely to bring snow to major cities in the northeast, Carbin said.
“It doesn’t feel like a blockbuster right now,” he said, speaking of the possible effects on the Northeast. However, “it could be completely different,” he said.
April Rubin contributed report.