Why Such a Long Period of Rain?

A large and anomalously deep upper level low pressure system formed over the Central Plains Friday (see the large swirl in the animation below).  This system was slow moving as it drifted into Arkansas during the day Saturday and then into the Tennessee/Mississippi border area so far today. 

The counter-clockwise flow wrapping around this low pulled Gulf of Mexico moisture into the region yesterday, which caused rain in the form of a slow-moving northwest to southeast orient.  As the low moved into Arkansas, the moisture feed from the Gulf stopped and instead we switched into getting moisture more from the Atlantic Ocean.  In addition, the band of moderate rains pivoted to more of an east-west orientation.  The loop below indicates 12-hour precipitation totals estimated from area radars.

 Below is the 2-day accumulated precipitation map across our area, based on data from automated weather stations as well as CoCoRaHS observations (from private citizens like you).

This upper low is not in a rush to clear the Deep South.  Below is one model's depiction of where the upper low will travel.  The green contours indicate how deep the low is, whereas the background color is the 12-hour accumulated rainfall for each image.  Notice that our area will continue to have higher rain chances over the next few days, but the coverage should be more scattered in nature as the moisture stream in from the Atlantic becomes more limited over our region.

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