The storm system traveled across the Northern Pacific on Friday and will push into California over the weekend, forecasters with the Weather Prediction Center of the National Weather Service said in a short-term forecast on Saturday. The storm will continue to bring mountain snow and coastal rain to the West. Wintry precipitation will extend from the Great Lakes region into the Northeast on Sunday. The South could see heavy rainfall and thunderstorms. Computer modeling has given forecasters confidence in predicting the types of risks that will happen at the beginning of the week as the storm sweeps across the central United States. Here is what forecasters believe is likely to happen.
Extreme winter impacts are highly likely in the West this weekend.
The storm system began to move ashore Friday evening, bringing strong winds to the California coast. Heavy rain in the lower elevations that could lead to flooding. In the mountains, though, that moisture will fall as heavy snow. “The impacts will be widespread from north to south with numerous winter weather-related advisories in effect,” the Weather Prediction Center said on Saturday morning, adding that “the heaviest snowfall is expected for the Sierra Nevada” with several feet expected. Forecasters are predicting “extreme impacts” — the gravest warning on the Weather Service’s winter storm severity scale — across the Sierra Nevada this weekend.
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As this low-pressure system moves ashore, it will tap into an atmospheric river — an area of moisture that flows through the sky like a river at a level of the atmosphere near where planes fly. The combination will allow for the snowfall total to reach one to three feet across much of the higher terrain. More than five feet of snow is expected in parts of the Sierra Nevada, forecasters at the Prediction Center wrote. At least 20,000 customers served by the Sacramento Municipal Utility District were without power on Saturday morning as a result of the stormy weather.
Forecasters believe blizzard conditions will happen across the Plains.
“We are increasingly confident that we will be dealing with a pretty significant Northern Plains blizzard next week,” said Greg Carbin, the chief of forecast operations for the Weather Prediction Center. The system will move out of the Rockies and begin to strengthen, increasing the chance of heavy snow and very strong winds through Wednesday across the Northern Plains. The wintry blast is possible from Colorado, including Denver, and northeast across the Northern Plains. Across the Dakotas, at least a foot is likely, Mr. Carbin said. “The potential does exist there for some really impressive amounts,” he added, as he expects this storm system will most likely slow down. Snow in the mountains of the Central Rockies and Arizona could reach a foot by Sunday night.
Severe storms, possibly with tornadoes, are expected across portions of the South.
It looks highly likely that severe storms, possibly capable of producing tornadoes, will form on Tuesday across an area from eastern Texas across Arkansas, Louisiana and much of Mississippi, said Bill Bunting, the chief of forecast operations at the Storm Prediction Center. “Most fall and winter severe weather events typically have several features in common, including a low-pressure system near or north of the area of concern, a southerly flow of increasingly moist air from the Gulf of Mexico moving northward prior to the event and a cold front moving east towards the area,” Mr. Bunting explained. “A similar setup is expected early next week,” he said, “which gives us confidence regarding the potential for a focused area of severe thunderstorms and possibly tornadoes.” Tornadoes are not uncommon this time of year, but they are less likely than in the spring and early summer. “We average about four days in December per year with at least one EF1” — rated on a 0-to-5 scale of tornado damage — “or stronger tornado,” said Harold Brooks, a senior scientist with 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 the ones predicted next week can be more dangerous than ones that form during peak severe weather season, in May and June. “Because days are shorter,” Mr. Brooks explained, “they’re more likely to occur after dark,” he said of the storms. This “makes them more dangerous” because people in harm’s way cannot spot them as they approach, he said. “They also are more likely to occur in the mid-South and southeastern United States, which have greater rural population density than the Plains and have a higher fraction of manufactured housing and poverty,” he added. “Thus, the impacts can be greater.” Some snow is expected for southern New England, the interior Northeast and the central Appalachians on Sunday, forecasters said on Saturday. “Moderate snow totals between 3-4 inches are possible inland for higher elevation locations like the Berkshires and Catskills, and 1-2 inches are possible further south into central Pennsylvania,” the forecast said. The severe weather is likely to last through Tuesday night and into Wednesday. Deeper into the week, the forecast for what the storm may bring to the East is less certain. A coastal low is most likely but probably won’t bring snow to the major Northeast cities, Mr. Carbin said. “It doesn’t look like a blockbuster at this moment,” he said, speaking of the possible effects on the Northeast. However, “it could look completely different,” he said. April Rubin contributed reporting.
