A large storm system fueled in part by the remnants of Hurricane Polo is spreading deep tropical moisture into the central United States, setting up several days of heavy rain, flash-flood concerns, severe thunderstorms and a noticeable push of cooler air later in the week.
Meteorologist Max Schuster, host of the Max Velocity – Severe Weather Center YouTube channel, said Polo’s moisture is being drawn into a powerful upper-level low, creating an unusually wet setup from the Southwest into the southern and central Plains before the system gradually shifts toward the Midwest and areas farther east.
“We have a very active next few days ahead,” Schuster said as he outlined the developing pattern.
His main concern is the combination of extreme atmospheric moisture and a slow-moving storm system, which could allow thunderstorms and heavy rain to repeatedly track over some of the same places.
Texas And Oklahoma Face A Major Flooding Threat
Schuster said one of the highest concerns on Wednesday, September 30, is centered on Texas and Oklahoma, where a moderate risk of excessive rainfall includes Tulsa, Oklahoma City, Wichita Falls, Abilene and the Dallas-Fort Worth area.
He said many locations could pick up 2 to 4 inches of rain, especially from Wednesday evening into Thursday morning, while some places could receive considerably more if thunderstorms repeatedly move over the same corridor.
A separate moderate risk also covers parts of Colorado and New Mexico, while a much broader area of elevated rainfall risk extends north toward Chicago and Milwaukee.
Schuster said light to moderate rain may last for much of the day across sections of the Midwest, though the moisture supply there is not expected to be as deep as it is across Texas and Oklahoma.
That difference is important because several inches of rain spread over a long period are generally easier for the ground and drainage systems to handle than the same amount falling over only a few hours.
By Thursday, Schuster expects the flooding concern to remain elevated along the Interstate 35 corridor, including Dallas, San Antonio and Killeen, with another moderate excessive-rainfall risk in place.
A large slight-risk area is also expected to extend toward Kansas City, St. Louis and Chicago, while parts of the Detroit area remain under a lower-end threat.
Severe Storms Could Develop If Skies Clear
Along with the flooding risk, Schuster warned that Wednesday could bring severe thunderstorms across portions of the southern Plains, although the exact threat depends heavily on whether enough cloud cover breaks apart during the afternoon.
He said one forecast model showed relatively little rain around early afternoon, which could allow sunshine to increase instability ahead of a strongly sheared environment.
If that clearing occurs, Schuster said supercells could develop from around Odessa toward Wichita Falls and nearby parts of Oklahoma, with damaging winds, large hail and isolated tornadoes all possible.
He described the tornado threat as conditional rather than guaranteed because widespread rain and clouds could limit the amount of instability available.
That uncertainty is a key part of the forecast. The same moisture responsible for the flood threat could actually reduce the tornado risk if thick clouds keep temperatures down and prevent the atmosphere from destabilizing.
Schuster said storms could begin forming during the mid-to-late afternoon before becoming more widespread toward the evening.
Once they cluster into a larger line, damaging wind gusts would likely become the main severe-weather concern, while isolated tornadoes could remain possible into the nighttime hours.
He also mentioned a separate conditional tornado risk in Kansas, where one or two supercells could develop near Hays along the warm-front region around the surface low.
Historic Moisture Is Feeding The Storm
Schuster said one of the most unusual parts of this storm is the amount of moisture being transported north from the remnants of Polo.
He pointed to precipitable-water values in Texas and New Mexico that are exceptionally high for late September, including readings near El Paso that rank among the highest observed for this time of year.
According to Schuster, the National Weather Service office in Amarillo also reported atmospheric moisture values around the top half-percent of the historical range for the season.
That is why the flooding threat could become particularly serious if thunderstorms begin training over the same locations.
Polo itself had been a remarkably powerful eastern Pacific hurricane, reaching Category 5 intensity three separate times before weakening over Mexico.
Its circulation is now being absorbed into the larger upper-level storm, allowing a deep plume of tropical moisture to surge into the Southwest and Plains.
The setup is notable because it combines several ingredients that often produce major rainfall events: tropical moisture, a slow-moving upper-level system and a frontal boundary capable of focusing repeated thunderstorms.
Rain Could Last Through Friday And Beyond
Schuster said the storm will remain widespread through Thursday, with additional rain continuing across Chicago, Davenport, Springfield and St. Louis.
He would not rule out an isolated severe thunderstorm near St. Louis on Thursday, including wind gusts around 60 mph and perhaps a brief spin-up tornado.
By Friday, the excessive-rainfall threat should become somewhat more scattered and less predictable, but Schuster still expects elevated flooding concerns around Dallas, San Antonio and surrounding parts of Texas.
He also expects a broad swath of rain to stretch from South Texas toward the Midwest and eventually into the Northeast.
The European model cited by Schuster showed widespread rainfall totals of roughly 3 to 6 inches in parts of the Midwest through Saturday, although much of that would fall gradually.
Texas and Oklahoma could receive similar totals in a much shorter period, creating a much greater flash-flood threat.
Other guidance showed even higher localized amounts.
Schuster said the GFS model had pockets approaching 10 inches near Dallas-Fort Worth, while a National Weather Service blend of models suggested broad 3-to-6-inch totals with areas above 7 inches near the Red River Valley.
He added that some individual counties could ultimately exceed a foot of rain before the event ends.
That is an unusually large amount of water for a multi-day storm, and even if the highest model totals do not verify exactly, Schuster’s broader point is that the flooding risk should not be judged by one specific forecast number.
Cooler Air Follows Behind The Storm
Behind the heavy rain and thunderstorms, Schuster said a cold front will begin pushing cooler air south and east through the central Plains, Midwest and eventually parts of the South.
Dallas could still reach around 95 degrees on Wednesday, while St. Louis may be near 88, but temperatures are expected to fall noticeably behind the front later in the week.
By Thursday and Friday, cooler air should spread deeper into the central Plains and Midwest, with nighttime temperatures dropping into the 40s in some northern areas.
By Saturday, Schuster expects lows in the 40s and 50s to extend as far south as portions of the Texas Panhandle, while Dallas could fall to around 69 degrees.
The cooler air is not expected to surge deeply into the Gulf Coast, but parts of Oklahoma, Tennessee and Kentucky should get some relief by the weekend.
By early next week, Schuster said parts of Wisconsin could be near freezing, with frost possible in several areas and a chance that some locations briefly dip below 32 degrees.
He also noted that temperatures may rebound again across the northern and central Plains before another potential cold shot develops during the second week of October.
Another Tropical System Bears Watching
While the immediate focus is on Polo’s remnants, Schuster also said Tropical Storm Rachel could become a hurricane off the Mexican coast over the next few days.
He said the system will need to be watched heading into October because a farther-north track could potentially send another surge of moisture toward the United States and create an additional flooding concern.
For now, however, the more immediate issue is the storm already spreading through the country, with heavy rain expected across a large area from the Southwest through the southern Plains and into the Midwest.
Schuster’s forecast points to a complicated several-day period in which flooding is likely to be the most widespread threat, while severe weather remains possible where clouds break enough for stronger thunderstorms to organize.
The combination of tropical moisture, slow storm movement and a developing cold front means conditions may vary sharply from one region to another, but across the southern Plains in particular, the risk of repeated heavy rain is likely to remain the central concern through the end of the workweek.
Mark grew up in the heart of Texas, where tornadoes and extreme weather were a part of life. His early experiences sparked a fascination with emergency preparedness and homesteading. A father of three, Mark is dedicated to teaching families how to be self-sufficient, with a focus on food storage, DIY projects, and energy independence. His writing empowers everyday people to take small steps toward greater self-reliance without feeling overwhelmed.
