A dangerous severe weather outbreak is set to play out across the southern Plains Monday afternoon and night. Forecasters expect a swarm of tornadoes, widespread flash flooding, and a barrage of hail and wind.
Western and central Oklahoma and parts of the Texas Panhandle are expected to be hardest hit. The National Weather Service Storm Prediction Center has warned of the potential for an outbreak of "long track and violent" tornadoes in this area, which includes Oklahoma City and Norman.
Significant Tornado Outbreak Likely Today— NWS SPC (@NWSSPC) May 20, 2019
Long-track, fast-moving, and intense tornadoes will be possible today across parts of Texas & Oklahoma. Large hail and damaging winds also a concern.
Today's a day to plan ahead. Have multiple ways to receive weather information. pic.twitter.com/HEH2nYEmSa
The Storm Prediction Center has placed these areas in a rare "high risk" zone for severe weather reserved for only the worst events, which are "long-lived, very widespread, and particularly intense." Two million Americans are in this volatile zone. This is the first time the Storm Prediction Center has designated a "high risk" area since May 18, 2017.
"I have a feeling it's going to be one of those outbreaks that we never forget," tweeted Beth Carpenter, a meteorologist for TDS Weather, a consulting and forensics company.
"This is the rare kind of event that may take many lives," added Roger Edwards, an atmospheric scientist, long-time storm chaser and weather historian. "Pray I'm wrong."
The strength of the weather system predicted to trigger these storms is record-challenging, both near the ground and at high altitudes.
Storms will come in multiple waves, with repeated rounds lasting through much of the night. The first batch was already pushing through early Monday morning, heralded by several clusters of quickly-moving storms warned for three inch-diameter hail and torrential rainfall. As the initial burst of storms translates northeast through lunchtime, the atmosphere behind them will reload. And the results could be downright scary.
"I'd certainly label this 'the nightmare scenario'," tweeted Mike Smith, a meteorologist with decades of experience monitoring Midwest storms.
The atmosphere will be marked "extreme instability" according to the Storm Prediction Center, allowing for "rapid supercell formation. . . [and] a significant threat to life and property."
During the afternoon, these supercell storms, the most intense kind, are forecast to initiate just west and perhaps a little south of the Oklahoma/Texas border and well east of Interstate 27, tracking northeast at a breakneck 40 to 50 mph pace.
Additional rotating storms are predicted to form in southwest and south central Oklahoma south of Interstate 40 and west of Interstate 35 during this time. The Oklahoma City Metro area could be impacted as storms ride up the H. E. Bailey turnpike early Monday evening.
In an environment like this, conditions can change fast and storms will evolve rapidly. With the abnormally high amount of wind shear - rotational energy - present in the atmosphere, any storm that fires will begin to rotate.
Tornado probabilities are "off the charts", tweeted Sam Lillo, a Ph.D. student in meteorology at the University of Oklahoma.
The Storm Prediction Center wrote the combination of instability and atmospheric spin will likely yield "multiple significant" tornadoes, rated EF2 or higher on the 0 to 5 scale for twister intensity.
In addition to tornadoes, very large hail exceeding the size of softballs and straight-line winds topping 80 mph are possible in the strongest supercells.
With every thunderstorm yielding a risk for eventual tornadoes, forecasters urged residents to stay abreast of up to date weather warnings as they're issued, especially true during the overnight, when tornadoes are likely to continue.
"Have a safety plan, stay calm, and keep up to date with the latest weather information from a trusted source," the National Weather Service forecast office serving Norman tweeted.
As bad as the tornadoes might get, flooding could be equally dangerous.
The Weather Prediction Center - the branch of the National Weather Service that handles precipitation concerns - has also hoisted a high risk for excessive rainfall. Their forecast warns that "numerous, potentially significant flash flood events are likely," the greatest odds in the Oklahoma City to Tulsa corridor northwards. That's where storms will merge and eventually stall tonight, bringing with them a firehose of moisture.
Flash-flood watches blanket most of Oklahoma and adjacent northwest Arkansas. A widespread 4 to 6 inches with localized 8 to 10 inch amounts will fall just north of a stationary front, which will be draped along Interstate 40 and Interstate 44 during the overnight. The storms will last through daybreak Tuesday morning, finally clearing from west to east during the day.
Many of these same areas have already seen 200 to 300 percent their "normal" rainfall over the last two weeks, the sodden ground unable to handle much more water. And while currently predicted to meander just north of the city, if the band of heavy rain crashes south towards the Oklahoma City metro area, the results could be disastrous.
Coincident with the deadly May 13, 2013 tornado in El Reno, Oklahoma, which killed 8 people, 13 lives were lost in flash flooding in Oklahoma City.
Monday's bout of life-threatening weather comes on an already infamous day - May 20. In 2013, this date was marked by an EF-5 tornado that ravaged Moore, Oklahoma. It claimed 24 lives and leveled much of the same community that was slammed by an F5 in 1999. And six years since their last tornado disaster, the community is at risk again.
The city of 60,000 isn't taking any chances, joining hundreds of other school districts across the Sooner State to shut their doors Monday.
The University of Oklahoma cancelled classes Monday as well, offering students and faculty a list of storm shelters.