Severe weather has impacted portions of the Southern Plains already this week and more is ahead as the threat shifts more to the south and east midweek while heavy rains slam a greater region in the East.
On Wednesday, the threat for strong to severe storms, which may produce large hail, damaging winds, and a few tornadoes will primarily be in Texas, spanning from the Lower-Mississippi Valley through the Texas Gulf coast. A new developing, large-scale storm system over Texas while moving to the northeast, and eventually will reach the Northeast by Friday. All key ingredients for severe weather will be in place, although the strongest of the upper-level winds will be north of the warm sector of this storm system, so that will be a limiting factor and will prevent a severe weather and tornado outbreak.
Now we’ll time out those storms Wednesday into Wednesday night: a slow-moving line of storms from Tuesday night will set up from the Memphis area through eastern Texas while a steady, light to moderate rain affects the Ohio Valley. Then as we get into the afternoon, some of the model guidance is hinting at the development of a stronger line of storms, particularly in eastern Texas, while the line of storms from Wednesday morning weakens and eventually dissipates. This new line will be the one that produces the severe storms. In the afternoon, the worst of the weather will be in eastern Texas, then in the evening and overnight hours the strong storms will push eastward into the ArkLaTex region, Louisiana, Mississippi, and the western Tennessee River Valley. Meanwhile to the north and west, this storm system will bring a large shield of rain with embedded sockets of heavy rain to the Mid-Mississippi River and Ohio River Valleys Wednesday night. The greatest risk for flooding will be in the ArkLaTex and Lower-Mississippi Valley, a region that continues to experience river flooding from February’s heavy rain event. The map below shows all the river gauges currently near or above flood stage. Notice how there is a higher density of areas experiencing river flooding in the Lower-Mississippi River Valley, which coincides with some of the heavier rainfall.
Then on Thursday, the threat for severe weather will shift east as well as the risk for flooding. This is due to the eastward movement of the large-scale storms. Severe weather will threaten portions of Dixie Alley, including portions of Louisiana, Mississippi, Alabama, Georgia, and the Florida Panhandle. Again, large hail and damaging winds will be the main threats, but a couple tornadoes are also possible.
A line of thunderstorms will slowly move eastward from the western Tennessee Valley down to the Louisiana Gulf coast in the morning to northern Georgia through the Mississippi River Delta during the afternoon. Then overnight Thursday, much of the dynamics responsible for producing the severe weather will weaken as the line of storms moves through Georgia, the Florida Panhandle, and the Carolinas. To the north, rain showers will impact portions of the Ohio Valley in the morning, then into the Northeast during the afternoon and overnight hours. Also the eastern Great Lakes will deal with rain during the day Thursday, and northern portions of Lower Michigan may actually experience a changeover to snow for a few hours Thursday evening.
By Friday morning, no severe weather is expected as the line of showers and thunderstorms slowly clears out but not before continuing to impact much of the US East Coast from Maine through northern Florida. Then into the afternoon, showers may linger in parts of the Mid-Atlantic region. The rain showers and thunderstorms will continue into Friday night and Saturday for the Florida Peninsula.
Heavy rain and flooding remains a significant threat with this storm system, particularly in the ArkLaTex and Lower to Mid-Mississippi River Valley. That’s where a widespread three to five inches of additional rainfall is expected. Lighter rainfall amounts are expected as you get closer to the US East Coast between Wednesday morning and Friday evening.