-A few storms may move into western Ohio after 11:00PM, with the main severe threat occurring between 2:00AM and 11:00AM
-Anyone in Ohio could see severe weather, but the best chances will be in central and southern Ohio, where a fairly widespread threat may evolve Wednesday morning
-Widespread damaging wind gusts are the main risk, but a few tornadoes that spin up with a squall line are certainly possible
The forecast surface map for the middle of the night tonight shows a complex weather system affecting the region, with an intensifying low pressure tracking into the Great Lakes. A warm front is expected to lift north of Ohio this evening, with a cold front approaching from the west by Wednesday morning.
An unseasonably humid and unstable airmass will likely build in immediately ahead of the cold front tonight, with a very strong jet stream over the region leading to very strong wind shear across the region and strong winds in the low levels of the atmosphere. The combination of wind shear (change of wind speed and direction with height), instability (thunderstorm fuel), and lift from the cold front are expected to cause widespread thunderstorms to develop to our west this evening that track towards Ohio overnight into Wednesday morning.
There are two potential threats that we will watch for tonight:
-Threat 1 is the potential for scattered thunderstorms to develop ahead of the cold front across the Ohio Valley by late this evening and spread into Ohio (especially central and southern Ohio) after 11PM this evening. These storms will be on the leading edge of the more unstable air once they reach Ohio, so they may not be extremely strong. With that said, enough wind shear and just enough instability may exist for any scattered storms or perhaps a cluster of storms that moves in ahead of the front overnight to produce some hail up to the size of quarters, locally damaging winds, and perhaps a brief tornado.
-Threat 2 is the potential for a squall line to develop along the cold front to our west and surge east towards Ohio by early Wednesday morning, crossing from northwest to southeast between 3:00AM and noon. More substantial instability and stronger wind shear are expected to be in place ahead of the squall line, especially over the southern half or so of Ohio, and this may allow for the squall line to produce widespread damaging straight line winds and also a few spin-up tornadoes.
The threat with the squall line is still somewhat uncertain, especially in the northern third of Ohio, as it will be a race to get significant instability in place ahead of the storms early Wednesday morning. With very strong wind shear in place regardless, any somewhat organized storms could produce severe winds (around 60MPH) with little instability, which is why the entire state will need to watch the expected squall line early Wednesday…but the potential for a more widespread/high end event with perhaps a few tornadoes will depend on how much instability can build ahead of the storms.
The amount of instability that builds in ahead of the morning squall line will depend on both 1) how many storms move through ahead of the front, as those may block the instability from moving north and 2) how quickly the squall line moves east into Ohio; a slower squall line means more time for instability to build.
Because the instability will be coming in from the south, and because the squall line will take the longest to reach southern and especially southeastern Ohio, that is the area I feel most confident in a potentially widespread damaging wind event occurring in with the squall line. Farther north a severe weather risk certainly exists, and it may be rather widespread if enough instability builds in, but the prospects of a widespread event are much more uncertain in the northern half of Ohio.
If we get enough instability in place, our models are printing out some very impressive solutions with a potentially severe squall line affecting much of Ohio Wednesday morning. Because of the timing (near the morning rush) and out-of-season nature of this potentially widespread event, be sure to tell your family and friends to pay close attention to the weather later tonight into Wednesday morning, as severe weather with widespread damaging winds and a few tornadoes are possible across Ohio. Here is our assessment of the various hazards associated with this event; again, damaging winds, potentially widespread, are the main threat, but a few tornadoes and perhaps a little bit of hail can not be ruled out:
Be safe tonight into tomorrow, and prepare for some snow flurries by the end of the week, with potential accumulations in northern Ohio.
Meteorologist Jim Sullivan