SEVERE WEATHER: A major-impact severe weather event will unfold today across the Southeast, stretching from eastern Texas through Arkansas, Louisiana, Mississippi and Alabama, as far north as Tennessee and ending the day in Georgia and extreme western parts of the Carolinas. A level 4 out of 5 moderate risk is up for the cities of Jackson, Mississippi; Monroe, Louisiana; Hattiesburg, Mississippi; Alexandria, Louisiana, and Meridian, Mississippi. Outside of that, a level 3 out of 5 enhanced risk is up for Baton Rouge, Louisiana; Shreveport, Louisiana; Mobile, Alabama; Lafayette, Louisiana; Tuscaloosa, Alabama, and surrounding locations. A slight risk (level 2) and a marginal risk (level 1) are up circling the stronger-risk locations.

Everyone in Alabama is under some sort of risk for severe weather today:

• A moderate risk is up for locations along and west of a line from Geiger to Myrtlewood to Coffeeville to Chatom.
• An enhanced risk is up for locations along and west of a line from Hamilton to Hoover to Thorsby to Evergreen to Spanish Fort.
• A slight risk is up for pretty much the rest of the state, except for locations east of a line from Phenix City to Hartford (in Geneva County), which are classified in a marginal risk for severe storms.

THE SETUP: A strong midlevel trough is pushing eastward today, bringing with it a powerful jet stream that’s fueling this severe weather setup. At the surface, a low-pressure system is deepening over northeast Texas, with a warm front lifting northward through Arkansas, Louisiana and Texas. Scattered storms will begin developing this morning near the low, and the environment is already primed for large hail in northeast Texas.

This afternoon and evening, the severe threat will really ramp up. A moist axis of air — where dewpoints are climbing into the mid to upper 60s — will set up from southern Louisiana into western Mississippi. Combine that with a strengthening low-level jet, and we have a recipe for supercells capable of producing strong, long-track tornadoes. Areas along this moist axis, particularly across eastern Louisiana into central Mississippi, are where we could see the most dangerous storms develop.

Forecast soundings are showing incredible storm-relative helicity, a clear indicator of a favorable environment for tornadoes.

Later this evening, a severe squall line is expected to organize and race eastward across the lower Mississippi Valley. This line will bring the threat of widespread damaging winds, potentially exceeding 70 mph, and embedded tornadoes along the leading edge. By early evening, the line will become the dominant feature, moving quickly into Alabama and the Tennessee Valley.

Overnight, the severe line of storms will continue eastward, maintaining the risk for wind damage and tornadoes as it moves through Alabama, middle Tennessee and eventually into the southern Appalachians. While the storms will weaken somewhat overnight, the risk will not end until the system clears the region Sunday morning.

THE TIMING: Moving from west to east, the severe weather threat will start around 2-3 p.m. over the western and northwestern counties, affect the central locations starting around 4-5 p.m. and make it into the eastern and southeastern parts around midnight. The threats should be over by 1 a.m. Sunday in the west, 4 a.m. in the central locations and 8 a.m. Sunday in the east.

THE THREATS: We’re talking about the potential for tornadoes, some of which could be strong and long-lasting, damaging wind gusts up to 70 mph and large hail — potentially up to the size of ping pong balls in some of the strongest storms.

It will feel extremely muggy outside as the dewpoints will be very close to the actual temperature today. Afternoon highs are projected to make it into the mid 60s to the mid 70s across the state.

Make sure your family and friends are aware of this threat, and please share this information if you know someone in the affected areas. The time to prepare is now.

SUNDAY: Once we get the storms out of here Sunday morning, we can expect dry conditions with mild temperatures for late December, reaching the lower 60s to the mid 70s from north to south.

NEXT WEEK: A zonal flow will set up over the state on Monday, dropping moisture to much lower levels, keeping us dry with mostly sunny skies. Highs top out in the lower 60s to the lower 70s.

On New Year’s Eve, we’ll see a disturbance move across the Tennessee and Ohio River Valleys that may bring some very light rain to the north and northeastern counties, but the rest of the state will be dry with partly to mostly sunny skies. Highs will be in the upper 50s to the lower 70s.

On New Year’s Day, temperatures will be much cooler thanks to a surface high that will be moving eastward from the west. Skies will be sunny with highs in the upper 40s to the lower 60s.

On Thursday, we see cooler temperatures staying in place as that surface high gets close to us. Skies will be sunny with highs in the mid 40s to the upper 50s.

On Friday, the surface high will be centered over the Alabama and Mississippi Gulf Coast, continuing the streak of dry, cooler weather. Skies will be mostly sunny with highs in the mid 40s to close to 60 degrees from north to south.

For more weather news and information from James Spann, Scott Martin and other members of the James Spann team, visit AlabamaWx.