Heavy rain, thunderstorms to threaten the South into midweek

 By Brandon Buckingham, AccuWeather Meteorologist

Updated Feb. 28, 2021 2:54 PM EST

In the wake of bitterly cold air in mid-February across the South, milder air and rounds of rainfall are now bringing along a new set of hazardous weather conditions. As the calendar flips into March, the concern for flooding rainfall and locally severe thunderstorms is on the agenda for millions of Americans.

The rounds of rain began late this past week across the South, and have already led to flooding issues in some areas. Nashville was just one of many locales to experience flash flooding issues as thunderstorms dumped heavy rain across the area Saturday night. Before the end of the weekend, a wide swath of the Ohio, Mississippi and Tennessee River valleys can expect additional rainfall to further raise flooding concerns.

The rounds of rainfall have blossomed in response to a clash of air masses across the center of the country. As record-challenging warmth enveloping the Southeast attempts to expand northward, it has been met by a much colder air mass in place across the northern Plains and Midwest. This ongoing clash has resulted in a nearly stationary boundary between the two air masses, which has acted as a focal point for heavy rainfall.

A similar scenario will persist throughout the day on Sunday and into Sunday night across many of the same areas. Places like Evansville, Indiana; Louisville, Kentucky; Cape Girardeau, Missouri; Nashville, Tennessee and even Little Rock, Arkansas, can all expect moderate-to-heavy rainfall.

Along with the threat for flooding rain, there will also be a threat for some feisty thunderstorm activity Sunday afternoon into Sunday night. The colder air in place across the Midwest will advance southward and force the warmer air to retreat southward into early week. Along this advancing cold front, a threat for thunderstorm activity is expected.

Although threatening weather is anticipated along the front, drier conditions will lie in the wake of the stormy weather. For many of the previously mentioned locations, a turn towards drier and settled conditions are expected on Monday as high pressure expands into the region.

By the time the rain clears, a wide swath of 2-4, even 4-8 inches of rainfall is expected to tally up. Locally, double-digit rainfall totals will be possible across portions of Tennessee, Kentucky and West Virginia.

Although largely dry conditions will filter in by Monday across the Tennessee, Ohio and mid-Mississippi River valleys, there will continue to be issues in the wake of the wet weather. Many area rivers will likely continue to climb near, or into flood stage as water continues to run off.

The cold front that is expected to bring thunderstorm activity Sunday afternoon and night will continue to advance into the Deep South by Monday, bringing wet weather along with it. By Monday night, a new storm system is expected to develop in Texas along this frontal boundary.

The next wave of downpours will then traverse eastward across the South from Monday night, Tuesday and into Wednesday. Many locales along interstates 10 and 20 will be next in line for a soaking rainfall.

Along with the threat for localized flooding, embedded thunderstorm activity could also pack locally damaging wind gusts across the South into midweek.

Once this storm system slides off the Southeast coast by Wednesday evening, a reprieve from the wet weather will be in store across the South for at least a few day span into late week as high pressure settles overhead.

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