Flash flood watches and warnings were in effect across several states stretching from New Mexico to Wisconsin on Monday, as a narrow swath of soaking rain was expected to target the middle of the nation this week.
The combination of tropical moisture and a temperature battle zone will set the stage for the relentless rain, which could result in widespread flooding.
Repeated downpours will focus from eastern New Mexico and the Texas Panhandle to southern Minnesota, Wisconsin and northern Michigan, with the heaviest rain forecast to fall through Wednesday night.
A general 2-4 inches of rain is in store. However, up to 8 inches is predicted in portions of eastern Nebraska and northern Iowa.
While non-excessive rain is welcome in parts of western Texas, New Mexico, Oklahoma and southwestern Kansas, where abnormally dry to drought conditions exist, too much rain may fall in some areas and lead to or aggravate existing flooding.
Portions of the James, Missouri and Minnesota rivers over the North Central states were at or above flood stage to start this week from heavy rainfall over the past month.
"With soil across much of the Midwest nearly saturated, flash flooding is a prime concern," Brandon Buckingham, AccuWeather meteorologist, said.
"Chicago has received over 200 percent of their average rainfall for the month of September, and many other cities in Illinois, Iowa and Wisconsin have observed similar conditions," Buckingham said.
Enough rain can fall to cause periodic travel delays in the major cities of Chicago; Milwaukee; Grand Rapids, Mich.; Davenport, Iowa; Omaha, Neb.; Kansas City, Mo. and Topeka, Kan.
Motorists along portions of Interstates 10, 29, 35, 40, 70, 80, 90 and 94 can encounter blinding downpours and flooding in low-lying portions of roadways.
In addition to the flood threat, too much rain this time of the year, during harvest time, can negatively impact the harvest. Fields may be slow to dry out, which can inhibit the use of heavy machinery utilized during harvest.
While evaporation rates are much lower in the autumn, when compared to the middle of the summer, there is an increased chance of mold growth this time of year.
Any delays which put the harvest off can increase the chance of freezes damaging the crops later in the season.
Very warm, moist air will clash with chilly, dry air over the middle of the nation. This battle zone, combined with tropical moisture from the Pacific Ocean and a couple of storms riding northeastward in the corridor, will fuel the heavy rain.
Some of this moisture will be associated with Narda, a tropical system spinning near the western coast of Mexico.
Later in the week, the dry and chilly air will win the battle and sweep across the central and northern Plains and the Midwest from Thursday to Friday. A frost or freeze may occur in the normally colder locations of the North Central states to end this week.
Moisture is likely to linger in or quickly return to the Southwest with the potential for more downpours and localized flooding during Friday and Saturday.