AccuWeather.com

By Alex Sosnowski, Expert Senior Meteorologist

Apr 19, 2011; 6:44 AM ET

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It's time to run for cover if you see this heading your way. Severe thunderstorm photo by Evan Bookbinder, courtesy of the National Weather Service and NOAA.

As a relentless severe weather pattern continues, part of the Heartland will be the target for two severe weather events this week.

Two storm systems will roll out of the Rockies over the next several days, pulling together warm, moist air from the Gulf of Mexico, a sweep of dry air from the west, cold air aloft and a strong jet stream.

This is nearly the same setup as this past weekend, but there are some differences.

Both systems are destined to produce a swath of severe weather centered over the middle Mississippi and the lower Ohio valleys, rather than a sweep of tornadoes from west to east across the Southern states.

The atmosphere is also likely to be stacked differently with both forecast outbreaks later Tuesday and again later Friday, when compared to the violent tornado outbreak of this past weekend.

Instead of winds shifting greatly with height adding tremendous spin to the individual thunderstorms, the winds will be blowing nearly from the same direction near the ground and high over head during most of the upcoming outbreaks this week.

Relatively speaking, this setup favors damaging "straight-line" wind gusts over tornadoes.

However, there will be a brief period of time, at the onset of the outbreaks during the late afternoon hours, when winds will be shifting with height and could allow some tornadoes to get going.

Both forecast outbreaks this week are set to unfold in an area foretold by AccuWeather.com Chief Long-Range Meteorologist Paul Pastelok weeks earlier in the Spring 2011 Forecast.

While the storms will not so much tour the heavily populated South, they will roll through a heavily populated part of the Heartland.

Chances are that a portion of the large metropolitan areas of Tulsa, Little Rock, Memphis, St. Louis, Indianapolis and Louisville could be impacted by one or both of these outbreaks this week.

The details as to which specific metro areas, as well as rural locations would be hit won't be revealed until the storms actually form and start moving.

While both outbreaks this week are not likely to produce a large number of tornadoes, there can still be a tornado produced by a few of the strongest storms. People should not take these outbreak lightly as a result.

As Meteorologist Bill Deger put it when he warned of the outbreak for Tuesday, "Just one tornado passing through a populated area can lead to casualties and major destruction."

Straight-line winds may not be strong enough to destroy a home or business totally, but they can take off a roof or push a tree onto a dwelling or onto a passing car.

As Tuesday's outbreak unfolds then later matures it is expected to morph into a line of storms with damaging wind gusts, hail and blinding, perhaps flooding downpours into the nighttime hours.

A few gusty storms could continue to push eastward into part of the Northeast on Wednesday.

In the meantime, the late-week outbreak coming up could be a "repeat offender" for the Heartland considering what mess Tuesday's storms will bring.

The aftermath of the two outbreaks may not only be significant in terms of damage from winds and hail, but perhaps flooding as both systems may unleash inches of rain onto already taxed Mississippi and Ohio river basins.