Severe weather risks likely to return to US this week
By
Alex Sosnowski, AccuWeather senior meteorologist
Updated Mar 21, 2021 7:44 AM EST
Severe weather spawned dozens of tornadoes throughout the day and night across the Southeast on March 17.
As a multi-day severe weather outbreak was hammering areas from Texas to the Carolinas, leaving a trail of damage last week, AccuWeather meteorologists were already monitoring the potential for additional rounds of severe weather in some of the same areas this week. After a below-average number of tornadoes touched down in the first couple months of 2021, conditions are coming together for a potentially active start to spring, which officially begins on Saturday, March 20.
"The overall pattern this week is concerning and argues for at least some risk for severe weather in the Southern states, especially later on in the week," AccuWeather Chief On-Air Meteorologist Bernie Rayno said.
The parent storm that is forecast to trigger downpours and potentially severe thunderstorms this week will be a spinoff of a system that began impacting the United States on Thursday, spawning rain and high-elevation snow from Washington to Northern California.
This image captured during the early morning on Friday, March 18, 2021, shows a storm spinning offshore of the Washington and Oregon coasts. (CIRA at Colorado State/GOES-West)
This spinoff storm tiptoed across the interior West from Friday to early Sunday and produced spotty low-elevation rain and high-country snow from parts of Nevada, Idaho and Montana to portions of Utah and Wyoming. However, the storm will begin to tap into Gulf of Mexico moisture by the time it reaches Colorado later Sunday and Monday, where it is forecast to produce more significant snow as a result.
Ahead of the storm, another necessary ingredient for severe weather will be developing as warm air will surge over the Plains, Midwest and East through early this week. Temperatures are forecast to climb into the 50s, 60s and 70s F.
A river of high winds around the altitude where planes fly could then add some vigor to the weather setup.
"A strong jet stream that is forecast to dip from the Rockies into the central U.S. this week certainly means that at least some risk for severe weather returns to the South Central and Southeast states," Rayno said.
People who live in Dallas, Houston, Oklahoma City and Little Rock should all pay close attention to the forecast in the coming days as downpours could drench the area along with chances for more tumultuous conditions.
"The coverage and intensity of the severe weather this week may hinge on the overall strength of the storm system and the amount of cloud cover in the zone where thunderstorms are forecast to erupt," AccuWeather Senior Meteorologist Brett Anderson said.
For example, an extensive shield of clouds may limit daytime heating and could reduce the number and strength of thunderstorms that develop. Cloud cover was believed to be one suppressing factor to severe weather on Wednesday across the South, even though more than two dozen tornadoes touched down across the region. Wednesday was the most active day amid a three-day severe weather outbreak, but despite more than 300 incidents of severe weather and close calls for some individuals, there were no fatalities reported during the multi-day outbreak.
The downpours and thunderstorms forecast for this week will likely come in two main rounds.
"Should sunshine be out in force, the first storms this week may erupt over parts of western Texas and the southern High Plains starting on Monday," Anderson said.
As the storm system and associated southward dip in the jet stream head eastward, so will showers, thunderstorms and the potential for at least pockets of severe weather or isolated damaging storms during the early and middle parts of the week. Showers and heavy storms may extend from central Texas to Kansas, Missouri and Mississippi Monday night into Tuesday. Some of the storms could turn severe.
It is the later, second round of shower and thunderstorms that may be more troublesome.
"As one storm system lifts into Missouri and Iowa on Tuesday, it will fall apart, but another storm system is forecast to move eastward and into Texas by Wednesday night and Thursday," AccuWeather Meteorologist Ryan Adamson said.
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Just like the first storm system, the second one will pull in moisture from the Gulf of Mexico. The track and strength of this second storm will determine where the heaviest rain falls as well as the extent of severe weather.
"It is possible that both a flooding rain and severe weather threat extend as far west as central Texas, as far to the north as Kentucky and as far to the east as the Carolinas and Virginia during the middle to latter part of the week," Ryan added.
Communities that were struck by fierce winds, large hail, flash flooding and tornadoes, some rated as EF2 in hard-hit states like Alabama, last week may once again face risks from damaging thunderstorms.
"The bigger threat for severe weather this week may be Wednesday into Thursday from the central Gulf coast to the Carolinas," Rayno said.
Despite the recent uptick in damaging storms across the U.S., severe weather has been off to a slow start in 2021. The number of tornadoes is behind the average pace for this point in the season, based on data from the National Weather Service Storm Prediction Center.
Only 92 preliminary tornadoes have been tallied by the SPC as of March 18 -- or only 53% of the 16-year average (2005 to 2020) for the year to date. The average for this early point in the season is 173 tornado reports.
However, one change that has recently taken place in the Gulf of Mexico may be an indication that the trend of below-normal severe weather incidents is about to reverse in the U.S.
Major outbreaks of Arctic air in February not only wreaked havoc as the frigid air plunged all the way to the Gulf Coast of the U.S., leaving some communities to deal with the aftermath even weeks after the coldest weather, but it also helped to cool offshore waters. Gulf of Mexico water temperatures dipped to or below average levels in the northern and western parts of the basin. Chilly water in the Gulf can cool the air above, limiting or preventing thunderstorm development over the U.S.
This map shows Gulf of Mexico actual surface water temperatures in Celsius based on satellite data. (NOAA/GOES)
However, Gulf water temperatures had fully recovered by early this week and were generally climbing several degrees Fahrenheit above average for the middle to latter part of March. Sea surface temperatures ranged from the lower to middle 60s along the upper and western part coast to the lower 80s just west of Cuba on Tuesday.
When warmer water is present in the Gulf of Mexico, storm systems moving across the United States can more easily pull in warm and humid air that can swell across the South Central states up from the Gulf. Both warmth and humidity are necessary ingredients to fuel the development of severe thunderstorms.
Since Gulf of Mexico water temperatures have climbed to or above average levels, in areas from the Plans to the Southeast states, the tornado trend could swing toward average levels, putting more Americans at risk for damaging thunderstorms in the coming weeks.
The time of year and other weather elements could also play a role in the uptick in severe weather. The period from late March through May typically brings a substantial increase in the number of severe weather and tornado incidents across the nation due to strengthening sunshine, warmer weather as well as strong weather systems and a potent jet stream leftover from winter.
AccuWeather will continue to monitor the potential for severe thunderstorms and other threats to daily activities, lives and property in the coming days.
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier, Spectrum, FuboTV, Philo, and Verizon Fios.
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News / Severe Weather
Severe weather risks likely to return to US this week
By Alex Sosnowski, AccuWeather senior meteorologist
Updated Mar 21, 2021 7:44 AM EST
Severe weather spawned dozens of tornadoes throughout the day and night across the Southeast on March 17.
As a multi-day severe weather outbreak was hammering areas from Texas to the Carolinas, leaving a trail of damage last week, AccuWeather meteorologists were already monitoring the potential for additional rounds of severe weather in some of the same areas this week. After a below-average number of tornadoes touched down in the first couple months of 2021, conditions are coming together for a potentially active start to spring, which officially begins on Saturday, March 20.
"The overall pattern this week is concerning and argues for at least some risk for severe weather in the Southern states, especially later on in the week," AccuWeather Chief On-Air Meteorologist Bernie Rayno said.
The parent storm that is forecast to trigger downpours and potentially severe thunderstorms this week will be a spinoff of a system that began impacting the United States on Thursday, spawning rain and high-elevation snow from Washington to Northern California.
This image captured during the early morning on Friday, March 18, 2021, shows a storm spinning offshore of the Washington and Oregon coasts. (CIRA at Colorado State/GOES-West)
This spinoff storm tiptoed across the interior West from Friday to early Sunday and produced spotty low-elevation rain and high-country snow from parts of Nevada, Idaho and Montana to portions of Utah and Wyoming. However, the storm will begin to tap into Gulf of Mexico moisture by the time it reaches Colorado later Sunday and Monday, where it is forecast to produce more significant snow as a result.
Ahead of the storm, another necessary ingredient for severe weather will be developing as warm air will surge over the Plains, Midwest and East through early this week. Temperatures are forecast to climb into the 50s, 60s and 70s F.
A river of high winds around the altitude where planes fly could then add some vigor to the weather setup.
"A strong jet stream that is forecast to dip from the Rockies into the central U.S. this week certainly means that at least some risk for severe weather returns to the South Central and Southeast states," Rayno said.
People who live in Dallas, Houston, Oklahoma City and Little Rock should all pay close attention to the forecast in the coming days as downpours could drench the area along with chances for more tumultuous conditions.
"The coverage and intensity of the severe weather this week may hinge on the overall strength of the storm system and the amount of cloud cover in the zone where thunderstorms are forecast to erupt," AccuWeather Senior Meteorologist Brett Anderson said.
For example, an extensive shield of clouds may limit daytime heating and could reduce the number and strength of thunderstorms that develop. Cloud cover was believed to be one suppressing factor to severe weather on Wednesday across the South, even though more than two dozen tornadoes touched down across the region. Wednesday was the most active day amid a three-day severe weather outbreak, but despite more than 300 incidents of severe weather and close calls for some individuals, there were no fatalities reported during the multi-day outbreak.
The downpours and thunderstorms forecast for this week will likely come in two main rounds.
"Should sunshine be out in force, the first storms this week may erupt over parts of western Texas and the southern High Plains starting on Monday," Anderson said.
As the storm system and associated southward dip in the jet stream head eastward, so will showers, thunderstorms and the potential for at least pockets of severe weather or isolated damaging storms during the early and middle parts of the week. Showers and heavy storms may extend from central Texas to Kansas, Missouri and Mississippi Monday night into Tuesday. Some of the storms could turn severe.
It is the later, second round of shower and thunderstorms that may be more troublesome.
"As one storm system lifts into Missouri and Iowa on Tuesday, it will fall apart, but another storm system is forecast to move eastward and into Texas by Wednesday night and Thursday," AccuWeather Meteorologist Ryan Adamson said.
CLICK HERE FOR THE FREE ACCUWEATHER APP
Just like the first storm system, the second one will pull in moisture from the Gulf of Mexico. The track and strength of this second storm will determine where the heaviest rain falls as well as the extent of severe weather.
"It is possible that both a flooding rain and severe weather threat extend as far west as central Texas, as far to the north as Kentucky and as far to the east as the Carolinas and Virginia during the middle to latter part of the week," Ryan added.
Communities that were struck by fierce winds, large hail, flash flooding and tornadoes, some rated as EF2 in hard-hit states like Alabama, last week may once again face risks from damaging thunderstorms.
"The bigger threat for severe weather this week may be Wednesday into Thursday from the central Gulf coast to the Carolinas," Rayno said.
Despite the recent uptick in damaging storms across the U.S., severe weather has been off to a slow start in 2021. The number of tornadoes is behind the average pace for this point in the season, based on data from the National Weather Service Storm Prediction Center.
Only 92 preliminary tornadoes have been tallied by the SPC as of March 18 -- or only 53% of the 16-year average (2005 to 2020) for the year to date. The average for this early point in the season is 173 tornado reports.
However, one change that has recently taken place in the Gulf of Mexico may be an indication that the trend of below-normal severe weather incidents is about to reverse in the U.S.
Major outbreaks of Arctic air in February not only wreaked havoc as the frigid air plunged all the way to the Gulf Coast of the U.S., leaving some communities to deal with the aftermath even weeks after the coldest weather, but it also helped to cool offshore waters. Gulf of Mexico water temperatures dipped to or below average levels in the northern and western parts of the basin. Chilly water in the Gulf can cool the air above, limiting or preventing thunderstorm development over the U.S.
This map shows Gulf of Mexico actual surface water temperatures in Celsius based on satellite data. (NOAA/GOES)
However, Gulf water temperatures had fully recovered by early this week and were generally climbing several degrees Fahrenheit above average for the middle to latter part of March. Sea surface temperatures ranged from the lower to middle 60s along the upper and western part coast to the lower 80s just west of Cuba on Tuesday.
When warmer water is present in the Gulf of Mexico, storm systems moving across the United States can more easily pull in warm and humid air that can swell across the South Central states up from the Gulf. Both warmth and humidity are necessary ingredients to fuel the development of severe thunderstorms.
Since Gulf of Mexico water temperatures have climbed to or above average levels, in areas from the Plans to the Southeast states, the tornado trend could swing toward average levels, putting more Americans at risk for damaging thunderstorms in the coming weeks.
The time of year and other weather elements could also play a role in the uptick in severe weather. The period from late March through May typically brings a substantial increase in the number of severe weather and tornado incidents across the nation due to strengthening sunshine, warmer weather as well as strong weather systems and a potent jet stream leftover from winter.
AccuWeather will continue to monitor the potential for severe thunderstorms and other threats to daily activities, lives and property in the coming days.
Related:
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier, Spectrum, FuboTV, Philo, and Verizon Fios.
Report a Typo