11:30 p.m. Update: All Miami Valley Counties are cleared from the Severe Thunderstorm Watch. The severe weather threat is over. Just a few showers continue tonight.
10:30 p.m. Update: Clark, Greene, Clinton, Warren, and Butler County are still in the Severe Thunderstorm Watch. All other counties are clear of severe weather tonight.
10:00 p.m. Update: A line of thunderstorms will continue to track east into Champaign, Clark, Greene, Warren, and Clinton Counties. Wind gusts will likely be less than 45 mph. Storms are expected to stay sub-severe. Mercer, Auglaize, Darke, and Preble County are clear of the severe weather threat.
9:15 p.m. Update: All warnings have expired for the time being. The National Weather Service has issued a statement regarding Champaign, Logan, Shelby, Miami, Montgomery, Preble County. 50 mph wind gust are possible as the line of thunderstorms continues to move east across the region.
As expected there is less shear and instability on the eastern side of the Miami Valley. The storms aren’t able to survive at severe strength in this environment.
8:54 p.m. Update: Tree damage is being reported in southern Mercer County. Emergency Manager Mike Robbins reported a tree down across Watkins Rd. between Post Rd. and Tobe Rd.
Robbins is also reporting trees down on 112 St. at Route 119 in Fort Recovery.
Over the next three hours tree damage will be possible across the Miami Valley. If you have to drive, use extreme caution, otherwise stay home until the line of storms passes.
8:42 p.m. Update: New Severe Thunderstorm Warning for Auglaize and Shelby County until 9:15 p.m. More warnings will be issued as the line of storms continues to track to the east about 35 mph.
8:37 p.m. Update: Severe Thunderstorm Warning issued for northern Darke County until 9:15 p.m. This storm will track into southern Shelby County and northern Miami County north of State Route 36. The main risk will be 60 mph wind gusts. The storm is moving east at 35 mph.
8:28 p.m. Update: Severe Thunderstorm Warning issued for all of Mercer County until 8:45 p.m. The main hazard is 60 mph wind gusts. The strong part of the storm will move into Auglaize and northern Shelby county. It is moving east at 65 mph.
8:15 p.m. Update: A Severe Thunderstorm Watch was issued for the Miami Valley until 1a.m.
8:07 p.m. Update: Severe Thunderstorm Warning issued for Mercer County until 8:45 p.m. 60 mph wind gusts are possible.
The long-lasting line of storms will track across the Miami Valley over the next three hours. The system will weaken as the line of storms tracks ESE. Wind gusts will be 60 mph or less. The strongest part of the storm will track across the northern half of the Miami Valley.
8:00 p.m. Update: The Derecho is weakening. The strongest part of the storm is where there is a bow racing out ahead. This area is moving through Fort Wayne Indiana and will track into Paulding and Van Wert County just north of Mercer County. Radar is indicating 70-80 mph wind gusts.
There is a split happening in the line of storms. The strong forcing associated with the mesoscale convective system to our north is keeping the storms alive into northern Ohio. Forcing to the south will push the storms moving through Indianapolis south of the Miami Valley. This will lead to weaker storms moving across southwest Ohio.
5:30 p.m. Update: A Severe Thunderstorm Watch was issued for Indiana Counties along and north of I-70. Right now the watch is expected to expire by midnight. The Miami Valley will likely be added to the watch.
A line of storms called a Derecho is tracking east into Indiana. The line is considered a Derecho when the path of wind damage is more than 250 miles. Wind gusts are at least 58 mph with several gusts 75 mph or greater.
So far this squall line has produced a swath of damage almost 500 miles across Iowa and Illinois.
Severe Thunderstorm Warnings have been issued for northern Indiana. These warnings reach from South Bend to Union Indiana until 6:30 p.m. 70 mph wind gusts are possible.
Wind shear and convective available potential energy are both weaker across Ohio than Western Indiana. This will cause the line of storms to weaken as it approaches the Miami Valley. We are still expecting some wind damage, but the reports should not be quite as widespread as across Iowa and Illinois.
Wind damage is likely west of I-75 where there will be more instability fueling the squall line.
Original Forecast: An upgrade to a slight risk of severe weather by the Storm Prediction Center means the Miami Valley will see scattered severe thunderstorms this evening.
Areas west of I-75 have a greater chance of seeing severe thunderstorms with damaging wind gusts. The rest of the Miami Valley is under a marginal risk of severe weather.
The main threat will be wind gusts 58-65 mph. Additionally, there will be a period of heavy rainfall followed by stratiform rain that could result in some localized flooding.
The hail and tornado threat will stay just to the NW of the Miami Valley in northeast Indiana, northern Illinois, southern Wisconsin, and western Iowa.
A line of thunderstorms will move through the Miami Valley between 7 and 11 p.m. Monday evening.