Tuesday, December 31, 2019

Heavy Rain, Severe Weather Could Threaten the South Late This Week

Brian DoneganPublished: December 31 (New Year's Eve),2019



Heavy rain is expected across the South late this week, and a few severe thunderstorms might rumble near the Gulf Coast.
Abundant moisture from the Gulf of Mexico will surge into the region by Thursday. At the same time, a strong jet stream disturbance will punch eastward out of the Plains, which could trigger strong to severe storms in some areas.
While there will be plenty of wind energy in the atmosphere from that jet stream disturbance, the amount of instability that may develop remains uncertain.
If the atmosphere becomes unstable enough, thunderstorms could turn severe Thursday into Thursday night from southern Louisiana into southern Mississippi, southern Alabama and the western Florida Panhandle. The main threats would be damaging wind gusts, a couple of tornadoes and locally heavy rainfall.
Thursday's Severe Thunderstorm Forecast
The threat for a few severe storms might shift farther eastward into parts of the Southeast on Friday.
The exact areas that may be threatened is uncertain, but any storms that turn severe could have damaging wind gusts and locally heavy rain.
Friday's Forecast
What's more certain than the severe weather threat is the heavy rainfall.
NOAA's Weather Prediction Center has highlighted areas from the central Gulf Coast north and eastward into the Tennessee Valley and central Appalachians as having a marginal to slight risk of excessive rainfall Thursday into Thursday night.
Through Friday, much of this region could pick up 2 to 4 inches of rain, up to 5 inches in some spots. At times, the rain may fall at a half-inch per hour. Flash flooding might become problematic where the heaviest rain falls.
Rainfall Forecast
Some rain could linger near the Southeast coast and in Florida on Saturday, but most of it will sweep off the coast by Saturday night.

Wintertime Severe Weather Not Uncommon in the South

You would think that as it turns colder in the winter, there would be fewer severe thunderstorms.
But that isn't the case in the South.
The warmth and humidity from the tropics can periodically splash northward into the lower Mississippi Valley and near the Southeast coast as low-pressure systems cross the country.
The northern (polar) jet stream also intensifies during the winter months, which adds to the amount of lift and spin in the atmosphere.
Alabama had 139 January tornadoes in the 69-year period from 1950 to 2018. That's more than occurred in six other calendar months.
Shaded in red are the average tornado risk areas in early January.
Only a couple of weeks ago, severe thunderstorms spawned a tornado outbreak Dec. 16 and 17 across the Deep South from Louisiana to Mississippi, Alabama and Georgia.
National Weather Service damage surveys confirmed over 30 tornadoes in those four states from the outbreak.
Episodes of severe weather can continue through the winter from the lower Mississippi Valley into Florida, especially in years when the jet stream is stronger than average.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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