A flood threat is brewing from the eastern Southern Plains through the Ohio Valley, as we explained in our general flood outlook. Now we’re going to take you day-by-day and time out when you can expect the rain and how much will fall.
On Monday, or President’s Day, much of the activity will be in the Great Lakes region and Ohio Valley. Deep moisture will stream in from the south and a disturbance off to the west will allow for the widespread development of a moderate to heavy rain in this region. So during the morning on Monday, there will be a line of rain with embedded thunderstorms likely spanning from central Missouri through much of Illinois, Indiana, Ohio, and into western Pennsylvania. Surrounding areas will deal with scattered showers throughout the day. Into the afternoon, this shield of rain will pivot north, bringing showers and thunderstorms into much of the Midwest and Great Lakes region. Meanwhile, a steady but light rain will extend into portions of the Northeast and much of New England. In the Southern Plains, a dry line will lead to the explosive development of a line of strong to severe thunderstorm across eastern Oklahoma and Texas. Damaging winds up to 65 mph and a couple tornadoes are expected based on the atmospheric dynamics present.
Overnight Monday, those dry line thunderstorms will collapse and diminish by midnight as the atmosphere becomes stable or unfavorable for strong thunderstorms. Scattered showers and thunderstorms can be expected across portions of the Southern Plains while a moderate rain continues across the Great Lakes region into portions of the Midwest and Northeast.
On Tuesday, our first significant flood event will begin to shape up as the day progresses. The day will start off relatively quiet with lines of showers and thunderstorms spanning from the Southern Plains through the Midwest, while showers continue near the Canadian border of the Northeast. As we get toward the late-afternoon and evening, however, a widespread line of heavy rain and thunderstorms will develop from the Quad Cities and the Chicago area southward through the ArkLaTex and into eastern Texas.
The flood threat becomes real serious Tuesday night as this line stalls, especially from southern Missouri through northeastern Texas. With hours of rain dumping up to two to even three inches per hour, flooding is very likely to occur in some locations. This heavy line of rain will span Tuesday night from the eastern Great Lakes through the western Ohio River Valley, down into the Mid-Mississippi Valley, and as far south as eastern Texas. Even though the best chance for flooding is in that specified area we just mentioned, really any areas that experiences this heavy rain is at risk based on how much atmospheric moisture will be in place. Remember, this moisture originates all the way from the eastern Pacific near the Equator, so we are talking about deep, highly anomalous, tropical moisture. In addition to these heavy rainfall rates, this rain will be “training.” When we talking about “training,” this really means the precipitation will be moving over the same areas for several hours. In this setup, the rain will be moving from the south-southwest to the north-northeast without making any eastward progress.
On Wednesday, the flood threat will continue across very similar areas. In the interior Northeast southward through the Ohio and Tennessee River Valleys, light rain showers are expected. It’s not until you get into the Mid-Misssippi Valley and the ArkLaTex when the heaviest rain will fall with this three inch per hour rainfall rates possible. It’s going to be raining all day long in this region, so rivers will rise, leading to flooding along its banks and just plain, regular flooding will occur as well because the ground won’t be able to handle all of this rain.
As we get into Wednesday night, the rain will persist. We think the intensity of the rain will decrease as the night progresses from eastern Texas through the Mid-Mississippi Valley, but it’s more rain and more rain will lead to a further worsening of the conditions. Meanwhile in the Ohio and Tennessee River Valleys, the rain may become moderate to heavy, so the flood threat may increase there. Of course we’ll have more confidence as we approach this time period, but it’s hard to talk specifics a few days out in time, especially when you’re forecasting flooding and rainfall intensities.
We’ll keep you updated throughout the week on this flood threat with frequent updates on the latest timing and impacts you can expect. If you encounter flooding, remember to turn around, don’t drown!