Severe weather, tornado risk to return to southern US
AccuWeather forecasters say tornadoes will be possible as another round of severe weather takes aim at the southern U.S.
A new round of severe thunderstorms, including some capable of producing tornadoes, will rumble across the southern United States from Wednesday to Thursday night, AccuWeather meteorologists say. Areas at risk for this week's round of storms include some of the same cities and towns that were hit hard by damaging and deadly severe weather just one week earlier.
Severe weather that erupted last Wednesday and reached a frenzied peak on Thursday produced at least 300 severe weather incidents, including more than 30 confirmed tornadoes. Nine people lost their lives in the storms.
The first 16 days of January 2023 have been incredibly busy in terms of the number of tornadoes. There were even two more preliminary reports of tornadoes out of Iowa on Monday.
"As of mid-month, there have been 119 reports of tornadoes so far this January, which compares to an average of 39 twisters for the entire month," AccuWeather Long-Range Meteorologist Brandon Buckingham said. The actual number of confirmed tornadoes is subject to change pending further official investigation by National Weather Service storm survey crews.
A developing surge of warm air will likely be enough to again give storms more of a boost than what would typically occur in the winter. Meanwhile, the storm system will likely have a strong enough jet stream to support multiple severe thunderstorms capable of producing strong wind gusts, hail, flash flooding and at least a few tornadoes.
An AccuWeather Local StormMax™ for wind gusts of 75 mph is expected within the strongest storms, comparable to that of a Category 1 hurricane. At this force, property damage can occur, and large trees can be uprooted. Power outages could also occur, forecasters say.
Of the two severe weather threat days with this setup, the period from Wednesday to Wednesday night is likely to be the more robust of the two days this week. With last week's outbreak, Thursday was by far the more active of the two days.
The threat of severe weather will ramp up quickly on Wednesday from the northwest Gulf Coast region to the Ozark Mountains and the middle portion of the Mississippi Valley and to part of the lower Ohio Valley. A moderate risk of severe thunderstorms is likely to exist from near the Louisiana and Texas border to the borders of Arkansas, Tennessee, Kentucky and Missouri from Wednesday afternoon to Wednesday evening.
Some of the severe thunderstorms will persist through the nighttime hours on Wednesday as they move farther to the east and northeast in Mississippi, western Tennessee and western Alabama.
Along with the risk of severe weather on Wednesday and Wednesday night will be an elevated risk of urban and small stream flash flooding from northern Louisiana to southern Ohio. Since water levels have significantly dropped on the secondary rivers in the region since last week, the risk of river flooding is low. No flooding is expected on the Ohio and Mississippi rivers, as water levels are still recovering from historically low levels this past summer and were also receding from the rain earlier this month.
A small secondary pocket of severe weather may develop in portions of eastern Kansas from Wednesday afternoon to Wednesday evening, similar to conditions that produced isolated tornadoes in Iowa from late Monday.
On Thursday, the risk of severe thunderstorms will include some areas still recovering from last week's violent and deadly tornadoes.
Thursday's severe weather threat zone will extend from central Alabama to as far north as Ohio and western Pennsylvania. All modes of severe weather will be possible on Thursday, including the potential of a few tornadoes. However, overall, the severe weather threat is lower on Thursday, compared to Wednesday.
The historic city of Selma, Alabama, was among the hardest-hit locations during last week’s tornado outbreak. AccuWeather meteorologists say the city will be among those at risk for the next round of severe storms on Thursday.
What is causing all the severe weather, tornadoes?
"A weakening La Niña pattern, which has been occurring this month, along with some other factors over the Northern Pacific Ocean, has contributed to an uptick in the frequency of storms and storm intensity in California," AccuWeather Lead Long-Range Meteorologist Paul Pastelok said. "But, while there is a correlation between an uptick in severe weather in the Southern states and weakening La Niña in the spring, there is no direct correlation of the same for the winter season."
This graphic shows how warm air and cool air can combine to produce volatile outbreaks of severe weather. It does not depict the areas at risk for severe weather on Wednesday and Thursday.
The recent California storms have generally weakened by the time they push into the Plains, but thunderstorms have gotten a boost in intensity from unusually persistent warmth east of the Rockies following the disruptive outbreak of Arctic air around Christmastime.
It is possible that a large sea surface temperature difference in waters north of Hawaii over the Pacific may have contributed to a stronger jet stream that has carried the severe weather potential with it across the southeastern U.S., Pastelok said.
While California is expected to get an extended break from the storms that have dumped torrential rain and yards of mountain snow, the southern part of the jet stream branch is likely to remain active and is likely to lead to more rounds of severe weather for the Southern states in the coming weeks.
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