Strong tornadoes possible across the South this week

Another shot for severe thunderstorms and tornadoes, including some strong tornadoes, possible for the South on Thursday. A Level 4 risk of severe thunderstorms is in place Thursday for a good chunk of the South, including Jackson, MS; Memphis, TN; Birmingham, AL; and Nashville, TN.

The severe threat will start west of the Mississippi River early in the day and spread east throughout the afternoon and evening hours. It is possible parts of the Level 4 risk area may be upgraded to a Level 5.

Keep checking back for updates!

Live Blog: Tornado Outbreak Continuous Coverage

Severe Weather Outlook 1

This live blog provides a one-stop shop for our users to get the latest forecasts during the current tornado outbreak. In addition to descriptive graphics, we will also share footage as this event unfolds, along with periodic forecast discussions.

Update: Wednesday, March 17, 2021 at 6:08pm ET (5:08pm CT)
Update: Wednesday, March 17, 2021 at 6:04pm ET (5:04pm CT)

A dangerous tornado is currently passing across I-65, north of Birmingham, between Gardendale and Morris.

Update: Wednesday, March 17, 2021 at 5:04pm ET (4:04pm CT)

As of 3:58pm CT, a confirmed tornado was located near Bull City, moving northeast at 30 mph. This tornado-producing storm will soon begin in infringe on northwestern portions of the Birmingham metro region.

Confirmed tornado heading northeastward toward northwestern portions of the Birmingham, Alabama metro.
Update: Wednesday, March 17, 2021 at 4:43pm ET (3:43pm CT)

That blue dot on the right image indicates that debris is being lofted into the atmosphere by a strong tornado. This is the tornado that was near Brookwood, Alabama around 3:31 pm CT. It’s moving northeast at 20 mph. Radar imagery shared by chief meteorologist Marc Weinberg.

Update: Wednesday, March 17, 2021 at 4:33pm ET (3:33pm CT)

Extensive tornado damage over chicken houses in Wayne County, Mississippi from earlier this afternoon. Photo shared by Brian Emfinger (@brianemfinger on Twitter)

Update: Wednesday, March 17, 2021 at 4:12pm ET (3:12pm CT)

A confirmed and strong tornado remains on the ground with a storm that is now east of downtown Tuscaloosa, Alabama. The tornado is now just north of I-20, moving northeastward toward Brookwood.

Strong tornado moving in Tuscaloosa County, Alabama
Update: Wednesday, March 17, 2021 at 3:54pm ET (2:54pm CT)

A confirmed large and extremely dangerous tornado is 7 miles south of Tuscaloosa, Alabama as of 2:45pm CT. The storm is moving northeast at 30 mph. The National Weather Service has designated this as a particularly dangerous situation.

Radar over Tuscaloosa, Alabama as of 2:50pm CT
Strong velocity couplet on Radar southeast of Tuscaloosa as of 2:53pm CT
Update: Wednesday, March 17, 2021 at 3:40pm ET (2:40pm CT)

Clusters of supercells continue to head northeastward across the outlined region. Though surface temperatures may be slightly lower relative to areas nearby, vertical wind shear is very favorable for strong, potentially long-track tornadoes.

Latest region favorable for strong tornadoes in the near future.
Update: Wednesday, March 17, 2021 at 2:30pm ET (1:30pm CT)
tornado watch for western mississippi, southeastern Arkansas, and northern and northeast Louisiana until 7pm CT.
PDS tornado watch for much of western MS and across parts of northern/northeastern LA and southeastern AR until 7pm CT
Update: Wednesday, March 17, 2021 at 2:22pm ET (1:22pm CT)

The SPC has outlined a region across south-central Mississippi that has rapidly become favorable for the development of strong tornadoes.

Update: Wednesday, March 17, 2021 at 2:16pm ET (1:16pm CT)

From earlier in Wayne County, MS. . .

Update: Wednesday, March 17, 2021 at 1:43pm ET (12:43pm CT)

Another PDS tornado will shortly be issued across parts of western Mississippi, southeastern Arkansas, and northeastern/eastern Louisiana.

Outlined region expected to go under PDS tornado watch shortly.
Update: Wednesday, March 17, 2021 at 1:33pm ET (12:33pm CT)

Analogs indicate strong tornado potentially ongoing in Mississippi currently.

Update: Wednesday, March 17, 2021 at 1:27pm ET (12:27pm CT)

A confirmed tornado has already been detected 10 miles south of Goodwater, Mississippi and will cross over the Mississippi/Alabama state line. The Storm Prediction Center has outlined a region that could face impacts from a strong tornado within the next 1-2 hours or less.

Strong tornado threat exists across parts of the MS/AL border
Update: Wednesday, March 17, 2021 at 12:47pm ET (11:47pm CT)

A PDS tornado watch has now gone live across parts of Mississippi and Alabama until 7pm CT. We will make a better graphic in a bit.

A PDS tornado watch has gone live across parts of Mississippi and Alabama until 7pm CT.
Update: Wednesday, March 17, 2021 at 12:40pm ET (11:40pm CT)

Parts of Mississippi and Alabama now sit under a rare 45% tornado risk. These high probabilities have only been used a handful of times in the past. This means that there’s a 45% chance that a tornado will hit within 25 miles of a given point within the outlined region.

The probability that a tornado will hit within 25 miles of a given point in the outlined regions.
Update: Wednesday, March 17, 2021 at 12:20pm ET (11:20pm CT)

The Storm Prediction will issue a PDS (particularly dangerous situation) tornado watch shortly across parts of Mississippi and Alabama. Breaks in cloud coverage, along with strong, low-level transport of moist air from the Gulf of Mexico, have quickly allowed for the atmosphere to become unstable. Temperatures have already surged well into the 70s to near 80 across central and southern Mississippi.

PDS tornado watch coming shortly for outlined region
Breaks in cloud coverage have allowed for quick destabilization.
Update: Wednesday, March 17, 2021 at 12:00pm ET (11:00pm CT)
Severe weather outlook for Wednesday, March 17.
Severe weather outlook for Thursday, March 18.

Strong, violent tornadoes likely for parts of the South

A dangerous severe weather outbreak will unfold across parts of the country over the next three days. This severe weather outbreak will lead to strong, violent tornadoes, large hail and damaging winds.

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The severe threat will slowly shift east from Tuesday through Thursday.

Tuesday severe thunderstorm outlook
Wednesday severe thunderstorm outlook
Thursday severe thunderstorm outlook

Significant severe weather, strong tornadoes possible across the Mid-South and Dixie Alley Wednesday

Wednesday is shaping up to be the first significant severe weather and high-impact tornado threat for Dixie Alley and the Mid-South. A potent upper level storm system will approach the region, allowing a surface low to develop and intensify, pulling in deep moisture and warm air into the region.

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Upper-level storm system Wednesday afternoon
Surface dew points Wednesday afternoon
Temperatures Wednesday afternoon

With the increased moist and warm airmass at the surface, and colder air moving over the region with the approaching upper-level storm system, the Convective Available Potential Energy (CAPE) will be high in the Mid-South and Dixie Alley. The higher the CAPE values, the more unstable the atmosphere; thus, producing stronger updrafts, leading to more severe weather possibilities.

CAPE Wednesday afternoon (high values are in the gray/green and yellow/orange shaded area)

The approaching upper-level storm system will provide favorable wind speeds and directions across the region. Winds will change directions and speed with height, which provides a favorable environment for severe thunderstorms and tornadoes. This is known as directional and speed shear. Directional shear is wind direction changing with height while speed shear is the change in wind speeds with height.

Strong vertical wind shear is crucial for the development and longevity of severe thunderstorms, and wind shear looks favorable for severe thunderstorms late-Wednesday. From 500 mb (around 18,700 feet) down to 925 mb (around 2,500 feet), the winds change direction and speed, which suggests severe thunderstorms and tornadoes are possible with other favorable atmospheric parameters.

500 mb (around 18,700 feet) winds Wednesday afternoon
925 mb (around 2,500 feet) winds Wednesday afternoon

The aforementioned setup indicates not only significant severe weather is possible but tornadoes are also possible late-Wednesday. When looking at such a setup, it is important to look dive into the history and look at similar weather patterns in the past and investigate what they have produced. This is known as analogs.

Looking at the analogs, they indicate similar atmospheric events in the past have led to strong, long-track tornadoes across the region, so this event needs to be monitored closely! It should be noted: this is still far out so the specifics cannot be identified at this point but that will be ironed out over the coming days.

Severe weather analog
Long-track tornado analog
Significant tornado analog

This is supported by the significant tornado parameter values Wednesday afternoon across the region. The significant tornado parameter is a complex composite index, consisting of multiple ingredients. It factors in 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), and surface parcel LCL height (sbLCL). To put this in laymen terms, it’s a great tool to identify where strong tornadoes may occur. High significant tornado parameter values are forecast to be present, which suggest tornadoes, some strong or violent, are a possibility across parts of western Tennessee, Mississippi, and western Alabama.

Significant tornado parameter Wednesday afternoon

While there are considerable questions surrounding this event, it appears thunderstorms will develop early-Wednesday west of the Mississippi River in Arkansas and Louisiana. These storms will move east through Wednesday afternoon into Wednesday evening for areas east of the Mississippi River, including Tennessee, Mississippi, Alabama, and eventually Georgia, and the Florida Panhandle.

Due to the severe potential, the Storm Prediction Center has highlighted the Mid-South and Mid-Mississippi Valley for severe weather Wednesday. A Level 3 risk for severe weather is in place Wednesday for the red shaded area. This includes southwestern Tennessee, eastern Arkansas, northeastern Louisiana, Mississippi, and Alabama. A Level 2 and Level 1 risk surrounds the Level 3 risk in the orange and yellow shaded areas.

Wednesday thunderstorm outlook

Now is the time to prepare! Do not panic but have a plan in place in case a Tornado Watch or Tornado Warning is issued for your area. Make sure you have a few reliable sources to receive weather information from as this event approaches.

It is also a good time to refresh your memory on tornado terminology. A tornado watch means conditions are favorable for tornadoes to form. A tornado warning means a tornado has been indicated or spotted. A tornado emergency means a severe threat to human life and catastrophic damage to property is likely.

Tornado terminology

Multiple rounds of severe weather to impact central parts of the country over the next several days

Multiple round of severe thunderstorms will impact central parts of the lower-48 late this week through the weekend. Damaging winds, large hail, and isolated tornadoes are all possible with the intense thunderstorms.

A favorable spring-like pattern has setup across the lower-48, which will allow for multiple rounds of thunderstorms over the coming days. Deep gulf moisture has surged north into the Plains. This warm, moist air mass will help feed storms that develop across the region. Several “triggers” for storms will approach the region as the upper-levels of the atmosphere are ripe for thunderstorm initiation.

A potent storm system is out over the West Coast with a strong heat ridge over southeastern parts of the lower-48. This will allow areas of lift, which lead to thunderstorm development, to move out of southwestern parts of the country into the Plains. Each area of lift will lead to thunderstorm development each afternoon.

Thursday

Severe thunderstorms are possible Thursday. A Level 1 risk for severe thunderstorms exists from the Ohio Valley, southwest into northern Oklahoma. The main hazards are gusty winds and hail, but an isolated tornado cannot be completely ruled out. This risk area includes Oklahoma City, Tulsa, Louisville, Cincinnati, and Columbus.

Friday

A higher risk for severe thunderstorms arrives Friday afternoon as the storm system over the West Coast moves east into the Desert Southwest. A Level 2 risk extends from central Oklahoma down into northwestern Texas and the Texas Panhandle. A Level 1 risk surrounds the Level 2 risk. All modes of severe weather are possible. This includes tornadoes, hail, and wind. Oklahoma City, Tulsa, Amarillo, Wichita Falls, Lubbock, and Tulsa are included in the risk area.

Saturday

The severe risk increases over the weekend as the storm system moves toward the Plains. This will elevate the severe risk on Saturday with a Level 2 extending from western Texas, north into south-central Kansas. Tornadoes, hail, and wind are possible late-Saturday. The risk area includes Wichita Falls, Oklahoma City, Tulsa, and the western-half of the Dallas-Fort Worth Metroplex.

Sunday

The storm system moves into the Plains on Sunday, shifting the severe threat farther south and east. It is likely severe storms will continue overnight into Sunday morning just east of I-35, slightly weakening, before regaining strength Sunday afternoon, east of I-45. There is a Level 2 risk for eastern Texas, eastern Oklahoma, northern Louisiana, Arkansas, southern Missouri, and far western Mississippi. The main hazard is wind but an isolated tornado and hail cannot be ruled out. The risk area includes Little Rock, Shreveport, Tulsa, and the eastern-half of the Dallas-Fort Worth Metroplex.

It does appear a severe threat will shift east into Dixie Alley and the Tennessee Valley to start the work week but the details are still being ironed out.

Several days of severe weather expected from the Southern Plains to Mid-South

March 1st was the first day of meteorological spring, and now spring-like thunderstorms are in the forecast over the next several days. Severe thunderstorms will begin over the Southern Plains and slowly spread east into the Mid-South.

The severe thunderstorm event will be triggered by the jet stream plunging south over the western-half of the lower-48. This dip in the jet stream will create a nice uptick in moisture across the western lower-48, including parts of California and the Four Corners states (YAY!). What comes down, must go up! A seesaw will take place. As the jet stream dips over the western lower-48, the jet stream will surge north over eastern parts of the country, which will lead to well above average temperatures.

This pattern will set the stage for severe thunderstorms from the Southern Plains into the Mid-South as gulf moisture and warmth feeds north, east of the Rockies, along with strong winds and colder temperatures slowly spreading east in the upper-levels of the atmosphere.

Severe thunderstorm forecast

Wednesday

The first threat for severe thunderstorms begins Wednesday across the Southern Plains. The main area to see thunderstorms will occur from western Missouri, southwest into central and eastern Kansas, down into central Oklahoma. The main hazards are gusty winds and hail.

Wednesday thunderstorm outlook

Thursday

The severe thunderstorm threat continues Thursday, slightly shifting south. The main area to see thunderstorms will occur from southern Missouri, southwest into southern Kansas, down into central and western Oklahoma as well as western Texas. The main hazards are gusty winds and hail.

Thursday thunderstorm outlook

Friday, Saturday, Sunday

A more impactful severe weather threat begins Friday, continuing through the weekend as the dip in the jet stream out west begins to move east. This will allow the hail and wind threat to continue along with an uptick in the chance for tornadoes.

The enhanced severe threat will begin Friday across far southern Kansas, northern and western Oklahoma, extending down into northwestern Texas.

The severe thunderstorm risk area expands on Saturday from southern Kansas, all of Oklahoma, down through northern and central Texas.

By Sunday, the severe threat slowly shifts east into the Mid-South. Eastern Kansas, southern and central Missouri, eastern Oklahoma, eastern Texas, Arkansas, northern and central Louisiana, far western Tennessee, and far northwestern Mississippi will all be under the gun for severe thunderstorms.

All modes of severe thunderstorms are possible Friday, Saturday, and Sunday.

Friday thunderstorm outlook
Saturday thunderstorm outlook
Sunday thunderstorm outlook

As the dip in the jet stream advances east early next week, the associated cold front will seep into the Ohio Valley and Southeast. The thunderstorm threat will shift east, too, but there are too many uncertainties at this point for a severe hazard to be outlined.

Keep checking back for updates!

Snow possible across the Southeast overnight into Saturday

All eyes are on an upper-level low over the Southern Plains. This upper-level low will race to the east overnight into Saturday and begin to open into a shortwave over the Mid-South tonight. Despite the upper-level system opening into a shortwave, it will be rather vigorous as it moves into the Southeast on Saturday.

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As the shortwave treks over the Southeast, strong lift, and a gradual moistening of the atmosphere will occur. This will lead to an uptick in cloud cover across the South & Southeast beginning tonight and continuing through Saturday morning. A light band of precipitation should develop with the increased lift ahead of the shortwave overnight into early-Saturday morning across northeastern Alabama, northern Georgia, far southeastern Tennessee, southeastern North Carolina, and far western Upstate South Carolina.

Future radar 3:00 am Saturday

Initially, the precipitation from this band will fall into dry air at the surface; thus, the majority of the precipitation will evaporate before reaching the surface. This evaporation process will lead to a gradual moistening of the atmosphere, leading to precipitation reaching the ground Saturday morning. The precipitation band will increase in coverage and intensity throughout the morning hours Saturday. Here is where the forecast gets interesting. The temperature profile of the atmosphere is supportive of a rain/snow mixture. Almost the entire column of the atmosphere, from the ground to where the jets fly, will be below freezing. This will allow snow or a rain/snow to fall across the aforementioned regions.

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Future radar 6:00 am Saturday
Future radar 9:00 am Saturday
Future radar 12:00 pm Saturday

High-resolution models are suggesting .05″ to .20″ of precipitation falling across northeastern Alabama, northern Georgia, far southeastern Tennessee, southeastern North Carolina, and far western Upstate South Carolina.

Precipitation accumulation forecast

With temperatures supporting wintry weather, precipitation amounts of .05″ to .20″ would equate to a few areas seeing accumulating snow. Models are suggesting up to 1″ of snow possible.

Snow accumulation forecast

Firsthand Weather is forecasting flurries from northeastern Alabama, northern Georgia, far southeastern Tennessee, southeastern North Carolina, and far western Upstate South Carolina Saturday morning with light accumulations possible across the higher terrain of northeastern Georgia. Within this area of accumulations, due to banding, isolated 2″ amounts cannot be ruled out but most areas will see lesser accumulations.

It should be noted: this event is marginal. Slight deviations in weather variables may significantly change the forecast so keep checking back for updates.

Gulf of Mexico water temps to have big impacts on severe thunderstorms this spring

The northwestern Gulf of Mexico is still recovering from the February Arctic intrusion that impacted Texas. As of early-March, water temperatures are well below average. The below average water temperatures will undoubtedly have an impact on convection and severe thunderstorms west of the Mississippi throughout March.  

Current Gulf of Mexico Water Temperature

The Gulf of Mexico waters are an important variable in convection and severe thunderstorms for areas east of the Rockies. Generally speaking, when the Gulf of Mexico water temperatures are above average, this leads to more instability for convection and severe thunderstorms by supplying the atmosphere with added moisture and warmth. Instability acts as fuel for thunderstorms, and many times, the greater the instability, the stronger the thunderstorm if other variables are favorable. Thus, the added moisture and warmth bolsters instability, creating increased severe thunderstorms. 

Research shows the warmer the Gulf of Mexico water temperatures, the more hail and tornadoes occur throughout March, April, and May. With the water temperatures running below average in the northwestern Gulf of Mexico, it is possible this will have implications on convection and severe thunderstorms throughout the month of March due to the decreased availability of moisture and warmth added to the atmosphere. This may lead to less intense convection or a decrease in tornado and large hail frequencies during the month of March for areas west of the Mississippi River. It should be noted: severe thunderstorms are still possible throughout March but the frequency and intensity may be impacted. Areas farther east into Dixie Alley and the Southeast will likely not see a decrease in thunderstorm intensity and frequency as Gulf of Mexico water temperatures are above average in the eastern-half of the Gulf.

Above average temperatures are forecast for the region throughout March so this will allow the Gulf of Mexico water temperatures to slowly recover, possibly returning to average or even climbing above average by April, which could lead to an increase in severe weather during April and May.  

March Temperature Outlook

More Heavy Rain To Houston?

First, I would like to send my good thoughts to Houston and all the other communities and towns that have been impacted by Harvey across Texas and Louisiana. If there is anything Firsthand Weather can do to assist you all, please do not hesitate to send us a message!

The rain has begun to shift eastward to far eastern Texas, and towards Louisiana and Mississippi. This will allow for better weather conditions as damage assessments and cleanup begins. Unfortunately, numerical guidance is indicating the potential for deep tropical moisture to move into coastal areas of Texas and Louisiana by mid next week. A moisture axis in the southern Caribbean will move over the Yucatan Peninsula late this week/early weekend into the southwestern Gulf of Mexico. This may lead to the development of a surface low off of the Texas coast by early to mid next week.

This would aid in deep tropical moisture potentially being pulled into Texas as an upper-level low is situated across the Panhandle of Texas–leading to precipitation chances. At this time, it appears a surface cold front will be situated somewhere across Texas, which could enhance precipitation, too. As the low moves eastward, it will aid in precipitation chances for Louisiana.

Current moisture axis in Caribbean (GFS)

Deep moisture in southwestern Gulf of Mexico by Monday morning (GFS)

Deep moisture in southwestern Gulf of Mexico Wednesday afternoon (GFS)

Precipitation forecast through 7 days from NWS (please note: this map will change over the next few days and it looks plausible that higher precipitation amounts will shift northward)

This is still several days out, so a lot will change; however, this scenario is plausible and needs to be closely monitored. It’s to early to determine the strength of this low, but it is possible a tropical cyclone (TD or TS) could evolve. Any additional rainfall next week will quickly cause flooding. Keep checking back for updates!

Harvey May Re-intensify Dumping Feet Of Additional Rainfall

More heavy rainfall and tornadoes are expected late tonight through at least Wednesday for Houston as well as the surrounding areas. This is bad news for these areas because 30″ of rain has fallen in some areas. Currently, Tropical Storm Harvey is situated over Texas but is inching closer to the coast–likely reemerging over the northern Gulf by Monday morning. Harvey has maximum sustained winds of 40 mph at this hour with a slow movement of 2 mph to the SE.

NHC Cone

The position of Harvey and slow movement place Houston and much of southern Texas and central Texas in a favorable area for very heavy rainfall for the next few days. As aforementioned, once Harvey moves back over the Gulf of Mexico by Monday morning, it is possible that Harvey will re-intensify into a strong tropical storm (possible maximum sustained winds of 60 to 65 mph). Harvey will then move northeastward, slowly, making landfall just south of Houston by Wednesday morning. This scenario would aid in heavier rainfall rates and an increased tornado threat for much of the mid-Texas coast, upper-Texas coast, southern parts of north Texas, and western Louisiana.

European (Wednesday morning)

3km NAM Rainfall Totals (through Tuesday evening)

A big concern is tonight (Sunday night) for Houston and its suburbs. Short range guidance indicates a feeder band from Harvey may situate itself over this area. These feeder bands can produce rainfall rates of 4-8″ per hour and tornadoes. This will only exacerbate the flooding issues across Houston and do so during the most dangerous time for flooding (at night). The HRRR is indicating 10-24″ may fall over the next 18 hours in the Houston area.

HRRR Future Radar (tonight)

HRRR Rainfall Totals (through 18 hours)

Once Harvey moves inland, again, into Texas on Wednesday, the path becomes uncertain. The uncertain path, and the slow meandering of Harvey over the past few days, is because there is a lack of upper-level features to act as a magnet and steer Harvey out of Texas. The steering currents are too light, and Harvey is ‘stuck’ between a mid-level high to its west and the subtropical ridge across the southeast. This may change by late week into the weekend however, however. An upper-level trough appears to dig into the central plains, which may draw Harvey northeastward. This would place parts of northeastern Texas, southern Arkansas, northern Louisiana, and western Mississippi in a favorable area to see rainfall from the remnants of Harvey. The remnants would produce flooding for these areas. By Saturday, it is possible isolated areas in southeastern Texas may see 50-60″ of rainfall.

Spaghetti Plot

European (Friday morning)

WPC Precipitation Forecast (through 7 days)

Firsthand Weather will have updates as needed!