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Severe weather outbreak, possible ‘strong’ tornadoes forecast in Oklahoma on Sunday

It’s the Sooner State’s biggest storm threat of the year

The National Weather Service Storm Prediction Center's outlook for severe weather on Sunday. (NOAA/SPC)

5:40 p.m. update: Tornado watch issued for central Oklahoma until 11:00 p.m. (10 p.m. central)

Severe thunderstorms are forecast to rapidly develop over southwest Oklahoma over the next couple of hours before racing northeastward. “Supercells capable of strong tornadoes and significant wind damage are possible - especially along the I-44 corridor,” the National Weather Service warned.

Short-term models project the storms should sweep through Oklahoma City between around 8 and 10 p.m. (7 and 9 p.m. central).

Original article from 1:25 p.m.

An autumn outbreak of severe weather is predicted for parts of the central and southern Plains on Sunday afternoon and night, when a potent upper-level disturbance will swing across the area and spawn a slew of dangerous thunderstorms. Tornadoes, large hail and hurricane-force, straight-line wind gusts are possible.

The threat of dangerous storms and tornadoes is highest in central and eastern Oklahoma, where the National Weather Service Storm Prediction Center has declared a level 4 out of 5 risk of severe weather. This zone runs through Lawton, Oklahoma City and Tulsa.

The Storm Prediction Center wrote that atmospheric conditions “favor the potential for strong tornadoes, very large hail, and significant damaging winds as storms track across central OK — mainly after dark” in its Sunday afternoon forecast discussion.

Nighttime tornadoes are particularly dangerous because they offer few visual cues.

The level 4 risk is the highest Oklahoma seen this year and comes after a comparatively tranquil spring in what’s traditionally a severe-weather hot spot. Parts of the Mid-Atlantic and Northeast, including New Jersey, have experienced more tornado activity.

Inside a record-setting summer of severe storms in the Northeast

Meteorologists refer to October and November as a “second season” for severe weather because fall cold fronts swinging across the Lower 48 can spark storms as they collide with warm, moist air left over from summer.

Outside of the level 4 out of 5 risk zone in central and eastern Oklahoma, a broader level 3 out of 5 stretches all the way down to the Dallas-Fort Worth Metroplex.

The setup

Instigating the severe weather is a pocket of cold air and vorticity, or spin, aloft ejecting from the Southwest. That frigid air at high altitudes destabilizes the atmosphere, allowing pockets of near-surface air to rise explosively. The uptick in vorticity catalyzes this process by vertically stretching columns of air.

At the same time, a change in wind speed and/or direction with height, known as wind shear, will allow storms to rotate.

The trigger for the storms will be a combination of a cold front and dryline, or the leading edge of bone-dry desert air from the Southwest as it intercepts warm, humid air from the Gulf of Mexico. Unusually hot weather surged through the central Plains on Saturday, setting the stage for a clash of air masses; the town of Freedom in northwestern Oklahoma reached 102 degrees.

Timing

Rain was already present in the Texas Panhandle and eastern New Mexico behind the cold front midday Sunday. Computer models suggests scattered storms will erupt southwest to northeast along the cold front quickly during the late afternoon and early evening.

Those initial storms could be supercells or rotating thunderstorms, especially southwest of Oklahoma City, including along the H.E. Bailey Turnpike; cities like Chickasaw and Lawton ought to pay close attention. Any supercell will be capable of destructive hail at roughly the size of a baseball, straight-line winds to 80 mph and tornadoes, some strong.

Supercells may continue streaming northeast ahead of the line, coming precariously close to or over the Oklahoma City metro area before being ingested by the squall line by 10 p.m. By then, the dangerous squall will extend all the way south to near Dallas. Quick-hitting tornadoes, which are difficult to predict more than a few minutes ahead of time, could develop within embedded circulations in this line.

Storms will continue their rampage overnight eastward before withering near the Arkansas border and Ozark Plateau.

Additional dangerous storms are likely from north Texas through Oklahoma and into Kansas on Tuesday as a new storm system sweeps into the region.

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