OKLAHOMA CITY -- Twisters have formed in areas of Texas and Oklahoma that are currently under the most dire tornado warning forecasters have issued in the past two years.
The National Weather Service confirmed at least two "large and extremely dangerous" tornadoes Monday evening: one in Greer County, Oklahoma, and another in Dickens County, Texas.
Each advisory carried the following instructions:
An extremely dangerous and potentially deadly tornado is on the ground. To protect your life, TAKE COVER NOW!
More tornadoes were confirmed in central Oklahoma and western Texas, bringing the total number reported to nine.
Over 2 million people are in harm's way, with the NWS Storm Prediction Center issuing a threat level 5 out of 5 for violent tornadoes Monday.
Violent tornadoes make up only 0.5% of all tornadoes but account for about half of all tornado deaths, CNN meteorologist Brandon Miller said.
"You can almost smell them coming"
The Storm Prediction Center issued a rare "particularly dangerous situation" tornado watch for much of western and central Oklahoma, including the entire Oklahoma City metro area, until 10 p.m. Central Time.
The designation means that "an outbreak of tornadoes, including the risk of intense and long-track tornadoes" is expected across the watch area. The chances of tornadoes, including strong ones, severe wind in excess of 75 mph, and hail larger than two inches are all greater than 95%.
The watch area includes Moore, where a devastating tornado killed 24 people in 2013, including seven children from Plaza Towers Elementary School, which was destroyed in the tornado.
On Monday, the weather advisories brought back memories of the devastation, almost six years later to the day.
Amber Anderson lives right behind the school. In 2013, her husband and brother-in-law helped clear collapsed walls from the school's wreckage, she said.
Her other home was destroyed in 2013 and her family chose a new one behind the school that came with a large underground storm shelter.
She described the threat on the anniversary of the 2013 storm as "anxiety inducing." Just talking about it nearly brings her to tears.
She spent Sunday stocking up on storm shelter supplies, including boots and gloves in case they have to dig neighbors out of their homes, she said. It was one of the lessons she learned from the last tornado.
"You can feel it in the air. Once you've been in a tornado, you can almost smell them coming," she said, recalling a "misty, dirty lake water smell."
Tornadoes aren't the only threat
In addition to threats from tornadoes, more than 50 million people are at risk of other severe weather, including fierce winds, large hail and flash flooding, Miller said.
On top of that, "there is also a high risk for flash flooding from parts of Oklahoma and Kansas, where rainfall totals of 3-6 inches will fall on already saturated ground," CNN meteorologist Dave Hennen said.
Tinker Air Force Base, about 8 miles southeast of Oklahoma City, evacuated ahead of the storm.
Several airlines canceled afternoon and evening flights at Will Rogers World Airport in Oklahoma City to "prevent extended delays in other cities or to avoid having aircraft damaged due to high winds or hail," the airport said.
Destructive hail and brutal winds are also possible through Tuesday.
Oklahoma City and Texas cities such as Lubbock, Amarillo and Abilene could get pounded with baseball-sized hail and hurricane-force winds, the National Weather Service said.
After a brief break, the risk of severe thunderstorms will increase again, the National Weather Service's Fort Worth office said. It urged residents to have a "safe plan in place" for Tuesday.
52 tornadoes in 3 days
States such as Louisiana, Oklahoma and Texas are still reeling from weekend tornadoes and storms.
In the past three days, 52 tornadoes were reported across seven states, CNN Meteorologist Michael Guy said.
In Ville Platte, Louisiana, a possible tornado damaged more than 50 homes and businesses, CNN affiliate WBRZ reported.
Further west, the storm wiped out roofs, barns and trees in DeRidder, CNN affiliate KPLC reported.
"We woke up to the sound of glass breaking, and went in and saw the window in the kitchen was broken," resident Dorine Bearden told KPLC.
"Before, I had always told my husband it looked like we lived in a park," she said. "And when I looked out there, that park was gone. It was heartbreaking."