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Spokane, Washington  Est. May 19, 1883

Weekend storm to lash Eastern U.S. with severe weather, heavy rain, snow

By Matthew Cappucci Washington Post

A quickly intensifying storm system will march up the Tennessee and Ohio valleys this weekend, unleashing a menagerie of meteorological mayhem across the Eastern United States. Severe thunderstorms with an attendant tornado risk will be possible in parts of the lower Mississippi Valley and Mid-South, with the chance of heavy rains and strong winds along the Eastern Seaboard.

On the system’s cold side, moderate to heavy snows could plaster parts of the Midwest and Great Lakes. Blizzard conditions are possible, with winds gusting over 40 mph. A number of major airport hubs could be affected.

More problems are possible from the New York through Boston and into the Canadian Maritimes, where wind gusts of 50 to 60 mph or more could be in the cards. Weather model forecasts are already raising eyebrows among meteorologists, suggesting a roaring jet stream rushing into the storm. That would deliver powerful winds.

Widespread travel disruptions are possible, particularly for air travelers. Cascading flight delays could linger into the start of the workweek, given the geographic coverage of the system’s winds.

The system will feed off clashing temperatures. Ahead of the storm, readings of 15 to 25 degrees above average are likely to kick off the weekend in the East. Behind the storm, temperatures will drop 5 to 15 degrees below average in most spots.

An atmospheric river is currently drenching the Pacific Northwest. Rainfall amounts of 5 to 15 inches are possible in the higher terrain, with 3 to 5 feet of snow above 9,000 feet. That filament of moisture is being dragged east by a dip in the jet stream that will drop from the coast of the Pacific Northwest on Wednesday into the southern Rocky Mountains by Friday.

That same jet stream dip will energize the development of a new storm system over the Oklahoma and Texas Panhandle. That’s the system that will bring severe thunderstorms, heavy snow, strong winds and downpours to the eastern half of the nation over the weekend.

The severe thunderstorm risk will materialize on the warm side of the incipient storm system.

By Friday into early Saturday, mild air with temperatures in the upper 60s to near 70 will spread from East Texas north toward Arkansas and across Louisiana. Gulf of Mexico humidity will waft northward, too.

As the storm system traverses the lower and mid-Mississippi Valley, a cold front will swing east, inciting thunderstorm development.

As the dip in the jet stream sweeps over the lower Mississippi Valley, meanwhile, it will induce wind shear – or a change of wind speed and/or direction with height. That could encourage thunderstorms to rotate, presenting a tornado risk Saturday.

It’s too early to determine how widespread severe storms may be and whether tornadoes will be numerous or few. The National Weather Service Storm Prediction Center has outlined an area to monitor from eastern Texas to western Mississippi, including Houston, Little Rock and Jackson, Mississippi.

Severe storms could also develop Sunday in the southeast and even the Mid-Atlantic, but it’s too soon to pinpoint what areas might be affected.

Forecasting snow five days out is a low-confidence endeavor, but computer model projections suggest a band of moderate snow will probably fall from parts of the central Plains into the Great Lakes. This will come because of moisture wrapping around the backside of the storm center, falling where temperatures are near or below freezing.

While it’s far too early to pinpoint specific timing or totals, confidence is increasing in a swath of snow from northwestern Oklahoma to somewhere near or northwest of Chicago. Parts of Oklahoma, Kansas, Missouri, Illinois, Iowa, Wisconsin and Michigan could be affected. If you’re flying through Oklahoma City; Kansas City, Missouri; Springfield, Illinois; Des Moines; Chicago; Madison, Wisconsin; Milwaukee; or Green Bay, Wisconsin, keep close tabs on the forecast.

The snow may be accompanied by strong winds topping 40 mph. That could result in localized blizzard conditions. Accumulations of 6 to 12 inches are possible in the zone of heaviest snowfall, with lesser amounts surrounding that.

A line of heavy downpours will reach the Ohio Valley, middle Tennessee and the Mississippi-Alabama border by Saturday night. On Sunday, it zips through the Appalachians and affects the East Coast.

Rainfall amounts of 1 to 2 inches are probable. The rain will probably last six hours give or take in most locales, culminating in a final band of downpours along the actual cold front. Some thunder is possible, too, even as far north as New York City.

Southerly winds gusting 35 mph or more are possible ahead of the storm front, with gusts of 40 mph in the heaviest downpours right along the front. Thereafter, continued blustery northwest flow is likely into the start of next week for most of the eastern United States as temperatures tumble.

There are some indications that a low-level jet – a conveyor belt of strong winds screaming north ahead of the system – will dramatically strengthen south of New England. That means that Sunday night into Monday, southerly winds could top 60 mph at the coastline, with gusts to 70 mph not out of the question for Block Island, Rhode Island; Nantucket, Massachusetts; or Martha’s Vineyard, Massachusetts.

Winds will be less intense inland, mainly in the 45 to 55 mph range. That could cause scattered power outages in the Northeast and pose a problem for flights.

The jet will probably strengthen most quickly east of New York. That might spare the city from 60-plus mph gusts, but gusts over 50 mph are still possible.