The stage is set for a “high-end life-threatening” severe weather outbreak in the Southern and Central Plains Saturday afternoon and night according to NOAA’s Storm Prediction Center (SPC).
Unusually high potential exists for large, long-lived tornadoes and damaging hail from north central Texas to northeast Nebraska and western Iowa.
“The environment is very favorable for violent, long-track tornadoes Saturday,” said Russ Schneider, SPC director.
For only the second time since 2003, SPC has designated a section of Oklahoma, Kansas , Nebraska, and Iowa under a “high risk” of severe thunderstorms more than 24 hours in advance. Historically, most high risk assessments have only been issued within 24 hours of a storm threat.
History of high risk assessments
The last time SPC issued a high risk assessment more than 24 hours ahead of time was for the outbreak on April 7, 2006. During that outbreak (which spanned April 5-7), 73 tornadoes touched down, 13 people died and $1.5 billion in damages resulted.
Even within 24 hours, high risk designations are rare and typically issued only a few times a year. The last high risk assessment to be issued was on March 2 this year. The tornado outbreak which unfolded that day produced 65 confirmed twisters, claimed 41 lives (mainly in Indiana and Kentucky), and became this year’s first billion dollar weather disaster.
About 5.5 million reside in the area in the highest risk category Saturday said SPC’s Schneider. The primary population centers highlighted run through Wichita Falls, TX, Oklahoma City, OK, Wichita, KS, and Omaha, NE.
Schneider warned tornadic thunderstorms could develop rapidly.
Consider also some of these ominous statements from local National Weather Service offices:
A MAJOR SEVERE WEATHER OUTBREAK IS EXPECTED TO OCCUR BEGINNING LATE SAT AFTERNOON INTO THE OVERNIGHT HOURS. A VERY DYNAMIC ENVIRONMENT WILL BE IN PLACE WITH STRONG INSTABILITY AND IMPRESSIVE LOW LEVEL WIND SHEAR. . . .
STORMS THAT DEVELOP...ESPECIALLY THOSE PRIOR TO MIDNIGHT SUNDAY...WILL HAVE A GOOD LIKELIHOOD OF BECOMING SUPERCELLS. THESE STORMS WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL UP TO BASEBALL SIZE AND STRONG TORNADOES.
[CONDITIONS ARE] IDEAL FOR SUPERCELL THUNDERSTORMS AND STRONG/LONG TRACK TORNADOES
CURRENT INDICATIONS SUGGEST THAT A LARGE PORTION OF THE FORECAST COULD SEE A TORNADO OUTBREAK SAT EVENING. A LARGE CONCERN EXISTS THAT THE TORNADO THREAT WILL CONTINUE INTO THE HOURS AFTER SUNSET SAT EVENING
. . .
STUDIES HAVE SHOWN THAT TORNADOES AFTER DARK SIGNIFICANTLY INCREASE THE POTENTIAL FOR LOSS OF LIFE.
The meteorological setup
An energetic disturbance moving out of California will eject into the Plains. Rip-roaring upper level winds, over 120 mph, will bend around a dip in the jet stream over the Southwest and race into Plains, energizing developing thunderstorms associated with the disturbance. It will also foster turning of the winds with height, favorable for tornadoes.
These storms will be fed by accelerating warm, moist flow from the Gulf of Mexico’s record warm waters. The volatile mix of humid Gulf air and dry, cool air aloft from the west will set up an extremely unstable situation.
Schneider stressed there is uncertainty in the timing and location in the development of dangerous storms as well as in the numbers.
“How many of these storms will form is the real question,” he said.
Preparedness: a focus
Jack Hayes, director of the National Weather Service, urged residents in the Plains, to take this threat seriously, even as they are accustomed to severe weather at this time of year. He encouraged residents to monitor National Weather Service watches and warnings and seek shelter in a basement or in the interior of the lowest level of a strong shelter should a tornado warning be issued.