What would a cause a line of thunderstorms to move down from the northeast and smack Mississippi?

Question

storm moving from east to west (in opposite direction)? and no, i'm not confused with my directions. i saw it with my own eyes on the radar.

Answer 1

It is not uncommon for tropical systems.  However, since this is not tropical system, then here a couple of possibilities.

If this is a large scale event, this type of system is known as a "back door front".  This means the storm in not coming in from the usually entrance to your area, but it sneaking in from behind.  This type of pattern is usually associated with storms moving over a very amplified jet stream over the mid to upper middle latitudes and is dropping rapidly southward from Canada into the US behind the large scale ridge.  Colder air from the large pocket of air from Canada will then spread or fan out as it moves south of the westerlies or the weaker west of east moving jet that forms under the amplied ridge.  Once the airmass is south of this summer westerlies, it will fan or spead out as it moves southward.  If you are to the southwest of this entrance area, the front will approach you from the northeast.  As long as the air masses maintains a significant differences in temperature, density, and/or moisture, the front should remain strong.

If this is a smaller scale event, then this is likely the case of a very strong outflow boundary from a strong downburst from a thunderstorm in the Northeast. An outflow boundary can travel in any direction and remain strong for days as long as it is moving through a relatively uniform airmass.  If there are plenty of moisture ahead of it, this will "feed" on this moisture and the thunderstorms will continue.  It is rare to find one this far north to survive going south or southwest.  I know farther south, they can survive for over a day.  Example, I have seen an outflow forms over OK and travels southward.  It may reach South Texas in 36 to 48 hours with a line of showers and strong thunderstorms.  As long as the area this line is traveling is void of any major systems that may get in its way, it can travel many miles and survive to smack a location well to the southeast of where the line first formed.

Answer 2

Just glancing at a few things I see there is a area of low pressure just to the southeast of MS in the Gulf of Mexico.   Winds around a low rotate counterclockwise which would cause weather to come from the northeast and move to the Southwest.  As far as being tropical, I don't think it's tropical in nature YET but the National Hurricane Center is keeping a close eye on it

2210 GMT CORRECTION:  It is tropical now.

Answer 3

At the latitude of most of the US the weather patterns move from west to east, however close to the tropics the pattern is reversed, which is why hurricanes come out of the East Atlantic off the coast of Africa and hit the US Atlantic and Gulf coast like  balls careening in a pinball machine.  When the tropical storm gets to the interface between tropical weather patterns and temperate zone weather patterns it is anyone's guess where those suckers will go.   When Katrina hit New Orleans, God got bonus points.  

While weather patterns generally move west to east, under cyclonic circumstances the weather spins on an axis and it can come at you from any direction.