An exceptionally active weather pattern will send several large storm systems streaking across the country. Air masses will wage war, creating possible hurricanes and blizzards. Huge waves will batter the California coast, while feet of snow and hurricane-force winds will cover peaks in the Sierra Nevada. In the east, after the cold and snow over the weekend, warm rains and flooding may sweep northward next week.
The meteorological chaos, fueled by a strong El Niño weather pattern, will culminate in a possible outbreak of cold air in just over a week, which could plunge temperatures across much of North America.
Here are seven extreme weather phenomena to watch out for:
1. Snow storm on the East Coast this weekend
The first is a storm set to sweep across the mid-Atlantic into eastern New England this weekend. Cold air will wrap around it, bringing moderate to heavy snow inland while cold rain falls on the coast. Some ice could occur in western parts of Virginia and North Carolina.
Generally 4 to 8 inches of snow is likely from inland Pennsylvania to the southern Hudson Valley, with an additional band of plowable snow in New England off the immediate southern coast. Local totals may reach double digits, especially in Boston to Manchester, New Hampshire, the corridor and west toward Albany, New York.
“Uncertainty remains about the path and intensity of the system,” the National Weather Service forecast office serving Boston wrote. “This will affect [snow] totals, [precipitation] Species and precise impacts on our region.”
Near the coast, one inch of rain is expected. In between, the Interstate 95 corridor lies near the rain-snow line, but minimal snow accumulation is expected in New York City, Philadelphia, Baltimore and Washington.
The fast-moving storm will sweep in between Saturday morning and Sunday afternoon before moving out.
2. Big California waves are back this weekend
It's been about a week since large breaking waves sent seawater spilling into coastal communities in California and injuring several people. Offshore waves between 28 and 33 feet prompted high surf warnings, and a few breakers exceeded 40 feet. Now a new round of big waves is about to hit the coast.
Some call them “mathematical waves,” a loose term to describe sudden waves that are twice as tall as the surrounding waves. While confidence is high that coastal flooding in the Saturday-Monday timeframe will not be as severe as last week's incident, the weather service office serving Southwest California is urging residents to swim near lifeguards only and stay away from rocky jetties.
Along California's central coast, surf is expected to range between 10 and 16 feet, and 5 to 8 feet on Los Angeles beaches.
On Sunday, the European model predicts surf of 30 to 35 feet, thanks to a storm system rolling up the Pacific coast and churning up the seas.
3. Snow is falling in the Sierra this weekend
This same system will direct a narrow filament of Pacific moisture into California. Some of this moisture will be concentrated in the mountains, resulting in 1 to 2 feet of snow at higher elevations above 7,500 feet. At the highest mountain peaks, heavy snow will combine with winds of 50 to 100 mph to create whiteout conditions. The worst comes between Saturday and Sunday morning.
Winter storm watches extend from the Oregon Cascades to the Sierra Nevada northeast of Bakersfield, California. Visibility can drop to less than 800 feet in the high Sierra region between Madera and Tulare.
Snow in the Sierras – while annoying to travelers – would be beneficial to the water supply. The amounts so far this season are only 30 to 40 percent of normal.
4. The risk of a blizzard increases in the Midwest Tuesday into Wednesday
A new storm system will form somewhere in the southern Mississippi Valley around Tuesday. Because it is activated by high-altitude turbulence (a pocket of cold, low-pressure, high-circulation air), it will condense quickly. This powerful surface low should sweep across the Tennessee Valley and into the Midwest and toward the Great Lakes by Wednesday.
To the west, moisture flowing off its cold side will drop a band of snow, which could affect Kansas City, Missouri; Saint Louis; Springfield, Illinois; And Indianapolis. Chicago and Detroit may end up on the edge of the heavy snow area, so potential amounts there are uncertain. But wherever the big prize ends up, getting a foot in the door isn't out of the question.
“Current advice is to continue monitoring updates and develop a winter preparedness plan,” the weather service office in Indianapolis warned.
The back side of the storm will also see an influx of cold air that will collide with strong winds of over 35 mph. These winds will combine with falling snow, reducing visibility to less than a quarter mile, possibly for an extended period. This will cause a blizzard and possible power outages, especially in the eastern Great Lakes region.
5. Severe storms and hurricanes in the south on Monday and Tuesday
On the warm side of the same system, severe thunderstorms are likely as moist air blows northward out of the Gulf of Mexico. These thunderstorms will boom vertically to form an air mass characterized by wind shear, or a change in wind speed and/or direction with height. This could make some of them spin and produce tornadoes.
There's also a lot of jet stream energy aloft, so thunderstorms will likely mix some momentum with the ground in the form of damaging straight-line wind gusts.
The National Weather Service's Storm Prediction Center has already drawn a watching area Monday from Houston to Mobile, Alabama, and on Tuesday the threat will expand into southeast and northern Florida.
The agency warned that “the threat to supercells and short-line segments capable of producing tornadoes, large hail, and damaging winds” is expected.
6. Floods in the east on Tuesday and Wednesday
While it generates snow in the Midwest and whips up severe storms in the South, this same storm will send a wave of mild air and moisture toward the East Coast, bringing the potential for widespread heavy rain.
There is expected to be a massive footprint of heavy rain, with 1.5 to 2.5 inches from the Texas and Florida coasts all the way to the Maine and Canada border. In the northeast, heavy rain will fall following the weekend's snowstorm And Waterlogged December. The combination of heavy rain and melting snow could lead to river flooding.
Meteorologist Ryan Mau estimated that 61 trillion gallons of water will fall over the Lower 48 next week – “Immense even in summer” size.
The storm could have some similar characteristics to the one that struck the Northeast the week before Christmas, which not only produced major river flooding but also led to flooding along the coast and high winds that knocked out power to more than 800,000 customers.
7. Cold air outbreaks within 8 days or so
Computer models indicate a major cold snap is likely in the western and central United States in about eight to 10 days.
It appears that the significant reduction in the jet stream will allow bitter Arctic air to flow south, causing temperatures to drop below normal. Models have not yet agreed on how severe the cold air outbreak will likely be, nor on how far the cold will extend eastward.
As the cold penetrates a growing area of the lower 48, The probability of snowfall will increase in the middle of the month in the southern tierwhich has not yet seen much winter weather this season.
Jason Samino contributed to this report.
