CINCINNATI — Sunday is a 9 First Warning Weather Alert Day as we are tracking the potential for strong and severe thunderstorms.
A strong low-pressure system, already responsible for tornadoes in the Plains states this weekend, will move east over the Great Lakes and place the Tri-State in the sweet spot for severe thunderstorms Sunday afternoon and evening. In advance of this, the Storm Prediction Center has placed much of the Tri-State in an Enhanced Risk (Level 3 of 5) for severe weather Sunday.
9 FIRST WARNING: Much of the Tri-State has been upgraded into an Enhanced Risk for severe weather Sunday. All mode of severe weather will be possible. Damaging winds up to 70 mph, hail as large as 2", and as few isolated tornadoes are possible #WCPO @WCPO #CincyWX #OHwx #NKYwx pic.twitter.com/dOmPfFJrW2
— Brandon Spinner WCPO (@wxSpinner89) June 24, 2023
There will be two parts to Sunday’s rain; Non-severe early morning showers and storms. Afternoon storms that will most likely be strong and have a good chance at becoming severe. Let’s have a look at what our biggest impacts will be and have a closer look at the timeline.
STORM IMPACTS
Sunday’s storms will bring the potential for all forms of severe weather hazards. That includes damaging winds, large hail, and a few tornadoes. Severe straight-line wind gusts of 60-70 mph will possible along with hail up to 2 inches in diameter. Those are the primary threats for Sunday. Tornadoes will also be possible, but that threat isn’t as elevated as the previous two. The storm mode will determine how strong our tornado risk becomes. We may have a few strong singular supercells before the development of a squall line. If that is the case our threat for tornadoes would be a little bit higher within those supercells.
Within these storms we will also have some heavy rainfall. It is this localized heavy rain threat that could create some flooding issues. The better threat will be where the storms train in the same areas. Most areas should see 0.25” to 0.75” of rain, but within some of the heavier and stronger storms there could be between 2 to 3 inches. That would definitely bring the potential for some flash flooding.
TIMELINE
As mentioned above, the beginning of the day will start with some showers and storms, but those will not be much of an issue. It is the afternoon that we need to pay close attention to. Models have been trending later for the development of our severe weather threat, but the timeline could open as early as 3 to 4 p.m. It is more likely going to be closer to 6 p.m. that we will see storms fire to our northwest and push into the Tri-State. Because of the direction these storms will be moving, our threat will greatly be determined on where the storms fire first. Anything that develops near or north of Indianapolis has a much better chance at reaching us than something that fires up further to the south. These storms should be moving from northwest to southeast. Either way, our main window for strong and severe storms will be between 6 p.m. and 11 p.m. The threat should end by midnight as the cold front moves through.
While supercell storms are possible early, the storms will likely move through the Tri-State as a quasi-linear convective system (QLCS) also called a "Squall line." This is why we will have more of a damaging wind threat.
Areas within the squall line that you should look for are spots that show “bowing” segments. This is the indication of strong winds within a storm.
WHAT WE NEED TO WATCH:
When we forecast severe storms we look for many ingredients. Like baking a cake, you need the correct ingredients for things to come together. While there are many variables that can impact or inhibit storm development, there are four main factors we look for. I use the acronym of S.L.I.M. This covers Shear, Lift, Instability, & Moisture. Shear is a measure of the spin in the atmosphere, which you need for storms to turn and strengthen. Lift is what helps these storms develop with an upward motion to push the storms higher in the atmosphere. Instability measures the energy in the atmosphere for storms to feed off of. The higher those levels get, the stronger storms are able to become. Lastly, Moisture. You can’t have storms without moisture, but the higher the levels, the better the threat for strong storms & tornadoes.
Shear values look robust. The indications of 3.0 to 5.0 tell us that if there are storms, there will be a high likelihood that there will be rotation in them. These numbers also suggest that we could have a better chance for tornadoes. From here, we look to instability.
Values of 1,000+ are more likely to increase and develop severe weather, and once again you see that the highest values are to the west of I-75, but really all of our numbers are sufficient. These numbers may be lower depending on how much rain we see during the morning hours, but there should be enough of a window of clearing that these numbers are likely.
Next up: Moisture. Dewpoints of 65°F and greater are usually the target for severe storm potential and we will have plenty of moisture available for storms. Values are more likely to be closer to 70°F, which is plenty high. The only question is when and if we will have that lift component. Boundaries from the early day rain could act as that, or already developed storms can help with that as well. We won’t know whether that develops until the afternoon itself and that is the make or break for the afternoon storm threat.
As always, make sure to stay weather alert wherever you are on Sunday. We will have coverage for you on-air when needed, but you can also stream coverage on your WCPO mobile app as well as on our streaming app on your Roku, Amazon Fire, and Apple TV devices. Keep checking in for the latest updates as we go through the day.
