Severe weather woes continue this week across the storm-battered Southern Plains and Missouri Valley. At least three more consecutive days of severe weather are in store for the region this week after recent severe weather outbreaks produced nearly 100 tornadoes, baseball-sized hail, and flooding downpours over the course of the last week. Blinding downpours, flash flooding, and destructive straight-line winds will be the most common properties of the upcoming thunderstorms. On top of that, some storms will also be capable of producing colossal hail stones and violent tornadoes.
The pandemonium this week will first organize about a wobbling frontal boundary draped across a corridor from the Central Plains to the Northeast. Behind this boundary will flow cool, dry air from the Canadian Prairies. Heat and humidity from the Gulf of Mexico will be pumped into and over this boundary, forcing the development of thunderstorms each day within its vicinity. Meanwhile, Pacific-based low pressure will crawl across the desert Southwest and Rocky Mountains. Its slow northeastward motion will gradually drive a dry desert air mass against the steaming, unstable southern Plains. The clash of these three very different air masses will produce explosive results.
Instability will build over the South-Central US Monday as the sun fights a lid on convection and thunderstorm development erected by cloud debris from Sunday night’s severe weather outbreak. Sunday night’s storms ravaged the central and southern Plains with up to three inches of rain, 22 tornadoes, and at least three reports of hail exceeding the diameter of a baseball. The region will have little time to prepare as the lid on convection collapses by late afternoon, permitting the formation of strong thunderstorms in the vicinity of the cold frontal boundary in northern Kansas, south-central Nebraska, and the foothills of the Rocky Mountains in eastern Colorado. During the evening hours, storms will also develop ahead of the dry line in parts of western Oklahoma and western Texas.
Monday’s storms will be discrete at first. Aided by strong wind shear, storms will be able to grow into long-lasting, severe supercells with rotating updrafts. The updrafts in some of the storms will be strong enough to support dangerously large hail on Sunday night over western and Central Kansas and over the Texas and Oklahoma panhandles. The storms may also generate tornadoes, especially over Kansas’s I-70 corridor southwestward to the border with the Oklahoma panhandle, where shear, instability, and lift will be optimized.
Later into the evening, strong wind shear will help organize the storms into large clusters and quasi-linear systems. These complexes of severe storms will impact most of Oklahoma, Kansas, and central Missouri into the overnight hours. Isolated and generally weak tornadoes, damaging winds, frequent lightning, blinding downpours, and flash flooding will be the predominant threats with these storms.
The cold front and dry-line will make little progress Monday night into Tuesday, leaving the southern Plains and the Missouri Valley primed for yet another day of severe weather. This time around will prove to be especially violent. Heat and humidity will continue to build across the region while drier air from the Rocky Mountains spills on top of it aloft and pushes harder against it at the surface. The stacking of air masses in such away yields an impeccable degree of atmospheric instability. As soon as the sun burns away debris from Monday night’s storms, so much as a tap upward could prompt explosive thunderstorm development.
The southern Plains will find itself squeezed from the north by the southward-sagging cold front and from the west by the slowly-inching dry-line. Each will undercut the humid warmth ahead of them and generate a new round of supercell development. Further away from the boundaries, approaching Pacific low pressure will help drive the ascent necessary for thunderstorm growth.
The entirety of western Texas northward to the Oklahoma panhandle will be susceptible to dangerous and expansive supercells. Temperatures will drop rapidly with increasing height as the upward soaring air fueling the storms rapidly evaporates in the drier layers. This is the type of environment that could support exceptionally large hail, matching or exceeding the size of baseballs. The storms will move faster than Sunday night’s storms but will nonetheless move slow enough to devastate any vehicles or structures in its path while posing fatal threats to humans or livestock caught in the hail. Strong tornadoes will also be of concern, particularly across the Texas and Oklahoma panhandles and in parts of southwestern Kansas near the boundary of the cold front, including cities like Lubbock, Amarillo, and Dodge City.
The cold front and dry-line will both make progress southeastward and eastward, respectively, as evening becomes night. Supercells and other scattered thunderstorms across the southern Plains will organize into linear structures and race across the region. The line of storms will expand upstream overnight to impact parts of central and southern Missouri in addition to the central and southern Plains. Damaging wind, blinding downpours, and flash flooding will be the primary concerns with these complexes of storms Tuesday night, with the I-35 corridor from Dallas to Wichita taking the brunt.
The storms Tuesday night will not weaken until after day break Wednesday due to enhanced lift from upper-level low pressure and an intensifying low-level jet stream. That the line of storms will survive the night will permit them at least one more day of severity. Enhanced by daytime heating, the storms will muster more strength as the day progresses over the Arklatex northward into the Missouri Valley Wednesday. Damaging winds and flash flooding will be the primary threats.
Tuesday night’s storms won’t just be strong, they will also outpace the boundaries that initiated them. Racing well ahead of the cold front and dry-line, the atmosphere in the southern Plains will be primed for one more day of severe thunderstorm development Wednesday. Similar to each day prior this week, the supercells will be capable of producing extremely large hail and tornadoes.
Regardless of thunderstorm intensity, the Plains and the Missouri Valley are expected to be doused with an additional 2-4″ of rainfall through Wednesday night. As the following map from the Advanced Hydrological Prediction Service demonstrates, the region received up to 10″ of rainfall in just the last week. Flooding is already ongoing along stretches of major area rivers like the Arkansas and Missouri Rivers and their principal tributaries. With soils saturated and rivers starting to flood, rain runoff will be impeded from draining, and river flooding will worsen while flash floods become increasingly likely. Remember to “turn around, don’t drown” when approaching flood waters. It only takes 6″ of water to stall most vehicles. Nearly half of all flood-related fatalities are related to driving!
A tumultuous few days is ahead for vast portions of the south-central US. Tornadoes, baseball-sized hail, tree-toppling winds, and floods are all possible this week before the severe weather threat finally shifts to the Ohio Valley and the Southeast Thursday. Be prepared for when the severe weather strikes by stocking emergency kits with supplies including first-aid kits, prescription medications, matches, blankets, dust masks, batteries, flashlights, a battery-powered or hand-cranked radio, a wrench to shut off utilities, a manual can opener, three days worth of non-perishable food, and one gallon of water per person per day for at least three days. Be sure to head warnings from the National Weather Service and from local law enforcement to further ensure safety.