Heavy rain will continue to impact the Ohio Valley as well as the Middle and Lower Mississippi River Valleys for the next few days. Significant rainfall in southern Louisiana has already caused major and record level river flooding.
Current Weather Situation
A low pressure system across Louisiana/West Texas is connected to a cold front extending from the lower Great Lakes south through the Mississippi River Valley. This low is pumping very moist air into the central US and leading to heavy rainfall. This morning’s measurement (8/13) of moisture levels from the balloon sounding from the Little Rock Office was 2.44 inches. The graphic below shows that this value also known as Precipitatible Water or PW is approaching some of the highest values recorded since 1975 for Little Rock. (Note these balloon soundings are taken every 12 hours at select National Weather Service offices across the nation.)
Guest Contributor Sheldon Kuesselson provides further insight on the significant amount of moisture being ushered in from the Gulf of Mexico and Pacific Ocean to fuel this heavy rainfall event.
The graphic on the upper right provides insight at the lower layers of the atmosphere with the areas of deeper greens and yellows being higher moisture content. The graphic in the upper right as well as in the lower left shows the middle layers of the atmosphere. (Notice the graphic in the lower left shows the green area surging from off the Baja of California into Texas and the Mississippi and Ohio River Valleys.) Finally the graphic in the lower right provides insight of how moist the higher layers of the atmosphere are with and the deeper blues showing high moisture content. When you have a significant amount of moisture from the lowest through the highest levels of the atmosphere and a slow moving weather pattern, long duration heavy rain is fairly certain.
How much rain has already fallen?
Unfortunately southern Louisiana has been under the control of the low pressure system, for the past few days and significant rains have occurred since Wednesday (8/10). In the past 3 days, widespread 12 – 16 inches has fallen in Southern Louisiana (shown in the pinks in the graphic below) with pockets of 20+ inches of rain (shown in the white areas.)
With the low and cold front moving very little in the next few days, heavy rainfall will continue from the Ohio Valley into Louisiana.
For regions along and south of the front, areas of 0.75” to pickets of 2.5”+ of rain are possible today and tonight. Near the low pressure system in southern Louisiana, an additional 4” to 7”+ is expected.
Unfortunately, the heavy rain will continue for Sunday and into Monday with the bullseye on Sunday across northern Arkansas and southern Missouri and Illinois where widespread 1.5 to 3 inches are possible and pockets of 5”+. For Monday, the rain will extend from Northwest Ohio to Southern Missouri where another 1.25” to 3” is expected and again isolated 5”+ amounts.
The graphic below shows the 5 day total of broad 4” to 7”+ impacting the heartland to the lower Mississippi River Valley. These 5 day totals will cause widespread flooding in fields, creeks and rivers and could seriously impact farming operations.
Flash and River Flooding
This heavy rain in Louisiana has already led widespread flash flooding and to moderate to record level river flooding. Some of the hardest hit areas are in the Baton Rouge and Lafayette, LA areas. The Comite River near Baton Rouge has experienced record level flooding at both the Olive Branch and the Comite Joor Road River gauges.
Thankfully, the heavier rain for today will be farther west. But any additional rain in areas already in flooding is not welcomed.
For the remainder of the weekend, Minor to Moderate level River flooding is forecast for parts of Indiana, Illinois and Missouri as shown by the locations in the graphic below that have an inner green square but an orange (minor flood levels) or Red (moderate flood levels) outer square. These river forecasts only account for the precipitation expected into Sunday. So expect additional locations to have flooding as we move into Monday and Tuesday.
The major flooding levels are causing significate impacts for those in Southern Louisiana. As mentioned above the flooding impacts will worsen and expand north into the Mississippi and Ohio River Valleys.
Farmers, if you have machinery in the fields in low lying move it to higher ground to avoid being flooding. In addition livestock owners, consider moving your livestock to pastures/fields that have higher ground to avoid them being caught in a flooding situation.
The team at WxIntegrations will continue to provide relevant information and resources to help you better understand and prepare by incorporating weather impacts into your planning and response.