A long-lived bow echo with a history of producing large hail and damaging winds along its track is cutting through western Wisconsin at the moment.
Significant warm air/moisture advection is occurring ahead of its southern flank in northern Michigan, which will sustain this MCS into the afternoon hours where it could likely produce severe weather near Sault Ste Marie and along the northern shore of Lake Huron. Large hailstones and wind gusts to over 110 km/h are possible.
However, it appears that the MCS will get increasingly displaced from its supply of boundary layer CAPE as it passes Lake Huron in the evening hours, and the HRRR has it disappearing by the time it reaches Pembroke, although that’s pretty close to a modelled tongue of 1000-2000 j/kg SBCAPE that extends from Sarnia to Montreal.
Regardless of the disappearance of the current MCS, the potential for additional storms in Ontario and Quebec overnight is present. I had my doubts due to widespread capping and H7 dryness but at the very least, we should have some outflow boundaries to fire up some non-severe storms.
Finally, the presence of these nighttime storms will have an impact on tomorrow’s event in southern Quebec. Although a cloud debris bust is not anticipated, residual moisture could result in very high dewpoints, CAPE, prevent Montreal from hitting 30 C tomorrow, as well as pushing the quasi-stationary boundary farther south.
The strongest storms tomorrow may be located between Quebec City and Saguenay, but that could change because the remnants of today’s storms could easily affect northern areas for much of tomorrow, where a cloud debris bust could easily occur.