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Strong storm heads toward East Coast this weekend, bringing rain to Boston

Boston could see rain and thunderstorms on Monday.Jessica Rinaldi/Globe Staff

A dynamic storm system is forming east of the Rockies and will trek across the central and eastern United States while unleashing multiple weather hazards into Monday. Severe thunderstorms are possible in parts of the South on Saturday, with a large area of heavy precipitation advancing toward the East Coast later in the weekend. Strong winds, meanwhile, could rake coastal New England on Sunday night, with gusts near 60 mph at the shoreline.

The system is nestled within a significant jet stream dip - the same one that energized the deadly storm in the Pacific Northwest - and is adding wind energy and momentum to the upper atmosphere. That's why parts of the South could be facing damaging winds and an isolated tornado risk on Saturday, while the same jet stream energy could fuel potent gusts in New England on Sunday night.

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The storm is also feeding off strong temperature contrasts. Ahead of it, temperatures are some 20 to 25 degrees above average, while they'll crash to below-average levels in its wake. Even New York City and Boston could see highs in the 60s on Sunday before the system's strong cold front swings through, accompanied by downpours and perhaps thunderstorms.

On the storm's chilly backside, accumulating snow could blanket the Appalachians on Sunday night into Monday.

Drawing abundant moisture from the Gulf of Mexico, it will generate heavy rains from Mississippi to Maine over the weekend, producing totals of 1 to 3 inches. Nashville, Raleigh, Richmond, Washington, Philadelphia, New York City and Boston should all anticipate moderate to heavy rainfall.

Flight disruptions are possible given heavy rain and the system's expansive area of strong winds, particularly late Sunday into early Monday in the Northeast.

A more tranquil weather pattern looks to build in toward the middle of next week.


The setup

The jet stream dip will encourage the development of a low pressure system in the Oklahoma and Texas panhandles on Thursday. That low will sweep northeast toward the Great Lakes, swinging a cold front east. That front will touch off severe weather in the South and serve as the focus for heavy rains in the Ohio and Tennessee valleys, the Mid-Atlantic and Northeast.

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On the cold side of the system, a corridor of snow may fall over the central and northern Appalachians, particularly in Pennsylvania and New York state.

That main low-pressure system will slip into Quebec, but a secondary strip of low pressure will probably form on its trailing cold front. That will tug jet stream energy toward the New England coastline, boosting the likelihood of strong winds battering the coast. The onshore flow could also result in a small storm surge - or rise in ocean water above normally dry land - and minor coastal flooding.


Strong winds in the Rockies on Thursday

Wind advisories and high wind watches and warnings stretch from near Taos, N.M., north through Colorado and Wyoming, as well as the Nebraska Panhandle.

As the jet stream dip swings through the area, the high terrain will find itself poking into some of the strong momentum aloft. Mountain gusts of 60 to 70 mph are possible, with 50 to 60 mph gusts in the lower elevations of southeast Wyoming and northwestern Nebraska.

The strongest winds will occur through Thursday evening.


Severe storms in the South on Friday and Saturday

On Friday, a level 1 out of 5 marginal risk for severe weather has been outlined by the Storm Prediction Center. It extends from northeast of Dallas to near Little Rock.

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Initial storms that form late Friday are expected to be "elevated," or rooted in mild air a few thousand feet up layered atop a shallow bank of cooler air near the surface. That will limit the damaging wind and tornado risk, meaning small hail would be the primary concern.

By Saturday, increasing southerly winds ahead of the cold front will drag a filament of warmth and moisture over the Mid-South. A level 2 out of 5 risk of severe weather stretches from approximately Houston to Memphis. The main concern is for a squall line with scattered strong to locally damaging winds and a few embedded tornadic circulations.

At least some low-end severe storm potential may linger into the Carolinas and/or the Virginia Tidewater on Sunday as the cold front presses eastward.


High winds in the Northeast on Sunday night

On Sunday night, a swift jet stream, with winds of 80 to 100 mph just half a mile above the ground, will be slicing overhead in southern New England.

Some of that momentum may be mixed to the surface. Gusts of 35 to 50 mph will be common along and east of Interstate 95 north of the Mason-Dixon Line, with gusts of 60 mph at the coastline from the Delmarva Peninsula to Long Island to eastern New England. Some computer models simulate the potential for even stronger winds, especially in extreme eastern Massachusetts and Downeast Maine.

Isolated to scattered power outages are possible where the strongest gusts occur.

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Heavy rain and snow over the weekend

On the warm side of the system, which will be east of the system's track, a slug of rainfall will drop 1 to 3 inches. Heavy rain will first arrive in the Ohio and Tennessee valleys Saturday night, advancing toward the interior Mid-Atlantic and Northeast on Sunday and nearing the coast Sunday night into early Monday.

Anyone east of the Appalachians will see rain rather than snow as southerly winds draw up unseasonably mild air. To the west, moisture will be swirled to the cold side of the system. That's likely to result in a swath of snow from the Appalachians of West Virginia through Upstate New York and northern Vermont. The exact placement of the snow, as well as totals, can't be ascertained yet, but a few folks might wind up with 6 to 8 inches, especially in the higher elevations.

Much of this snow would fall Sunday night into Monday, after a period of rain.


Jason Samenow contributed to this report.