I’m thankful that more members of this site are appreciating that thunderstorm forecasts are at best a probability forecast (i.e. 30%). In other words, it’s no guarantee that one given location, even in a high risk area, will see a thunderstorm.
Nevertheless, the areas most at risk and therefore most likely to experience some travel issues tomorrow (Monday) are outlined in this post. An area of low pressure is expected tomorrow (Monday), and will likely produce some surface based heating, yielding up to 1000j/KG of CAPE across the Midlands and Northern England.
Moderate levels of shear are expected, like today. This is likely to produce the risk of some more organized thunderstorm development into the afternoon. Some isolated hail, gusty winds and flash flooding is possible in some localized areas. These thunderstorms are not expected to be particularly severe or widespread, but where they do form some travel disruption is possible. Again, not everyone will see these, they will be quite isolated in nature but could develop some organization into the north Midlands later in the afternoon.
As the flow becomes increasingly weak across northern England later in the day, storms may slow down and produce higher rainfall totals here. Up to 25mm is possible locally leading to a risk of localized flooding.