Accuweather.com, July 12, 2019 — While the worst may be over in terms of widespread heavy rain, pockets of showers and thunderstorms are likely to cause trouble at the local levels over the central United States into July.
A break from the rainfall in recent days was a sign that the weather pattern that contributed a great deal to the widespread flooding has come to an end.
“We no longer have large storms rolling up from the southwest or pushing directly eastward from the Pacific Ocean,” according to AccuWeather Long-Range Expert Paul Pastelok.
“Instead, less-frequent, smaller storms will tend to drop southeastward from western Canada,” according to AccuWeather Senior Meteorologist Brett Anderson.
“While these storms will pick up some moisture from the Gulf of Mexico as they move along, they won’t have so much water with them immediately,” Anderson said.
During much of March, April and May, one storm after another was rolling into the region. The storms packed a great deal of Pacific and subtropical moisture. May 2019 went down as the wettest on record for Nebraska, Kansas and Missouri, and Oklahoma recorded its second wettest May ever.
“We have begun to see more separation in storm systems, which will translate to longer breaks of dry weather over more areas than we have seen in recent weeks and month,” Pastelok said.
Even with the weather pattern changing, the response from the large rivers and an end to the flooding will not be immediate.
The middle portion of the Mississippi, as well as much of the Missouri and Arkansas rivers, has crested. River levels are forecast to fall slowly but over the coming weeks.
The high water levels have shut down most lock operations on the Mississippi River above St. Louis. The terminals have either been flooded or the force of the water is too strong for the lock to operate without damage.
The closed locks have stopped barge traffic over the upper part of the Mississippi River.
Barge traffic has also been affected on the Illinois and Arkansas rivers.
The fast flow of water has deposited silt and created shoals in some of the shipping channels, which has prompted dredging operations by the U.S. Army Corps of Engineers.
Farther south, the water is still rising over the lower part of the Mississippi River. However, with the opening of the Morganza Spillway above Baton Rouge, La., delayed indefinitely by the Army Corps of Engineers, there is hope that more water will not need to be released into the Atchafalaya River.
The release of water from Morganza and the Old River structure can lead to major flooding in the Atchafalaya Basin.
Still some bumps on the road to recovery likely
Even though the weather pattern moving forward in time suggests less rain less often, the region is not out of the woods in terms of localized heavy rainfall and the problems already set into motion.
“We certainly don’t expect rain-free weather for the region in the coming weeks,” Pastelok said.
This time of the year, complexes of thunderstorms are responsible for the bulk of the rain in the region. And this is likely to be the case in the coming weeks.
For example, instead of heavy rain for three days straight over a several-state area, it may only rain hard for part of a day every three days.
One such batch of showers and thunderstorms will progress across the Central states into Wednesday of this week.
That type of rainfall can allow the large river systems to handle the runoff and even continue to recede, but small streams may rise quickly due to prevailing wet ground.
“There is still some concern for a front to stall across part of the region late this weekend into early next week, which could cause showers and thunderstorms to repeat,” Pastelok said.
However, that setup is more likely to be in a narrow zone, rather than over the entire region.
In the coming weeks, barring minor setbacks, levels on the upper Mississippi should fall enough to allow locks to open and shipping to resume, although more dredging of the shipping channels may be needed.
Many fields and low-lying areas will remain underwater or too muddy to venture into for days, if not weeks, and the clock is ticking on the planting and growing season.