There are several areas worth watching for severe thunderstorms this Monday across the nation. Regions to watch include the interior Northeast, the Upper Midwest, and the northern and central Plains. A cold front associated with a low pressure tracking eastward across Canada will allow for strong to severe thunderstorms to fire up across parts of the Northeast. Back to the west, multiple weak areas of low pressure will develop on the leeward side of the Rocky Mountains. This process is known as “Lee Cyclongeneis,” and it’s these lower pressures that will be the main driving factor for the scattered storms that develop across the nation’s midsection.
In the Northeast, the radar is quiet this morning, other than the few spotty showers moving across the Ohio River Valley. It’s not until the afternoon and evening when the storms will really develop. A line of scattered showers and thunderstorms will begin to develop in the early-afternoon, spanning from the eastern Ohio River Valley down to the Appalachian Mountains. By the evening these storms will organize into a more widespread line. At around sunset, this line will likely be located from northern Vermont down through central Pennsylvania and as far south as West Virginia. Some of these storms will contain damaging winds in excess of 58 mph, but due to the modest levels of wind shear, most of these storms should remain sub-severe.
Overnight Monday, due to the loss in daytime heating, the line of storms will weaken and become more scattered. A few scattered storms will sneak into northern portions of New England, while showers with embedded thunder dwindle across parts of New York, Pennsylvania, and West Virginia.
Now over the Plains and Upper Midwest, it will be a quiet day overall. Thanks to the cold front passage over the weekend, the northern Plains and Upper Midwest will be cooler while to the south remains hot. It’s not until the late-afternoon when activity dramatically perks up. Several clusters of storms will develop across the western Plains along a dry line emerging from the Rocky Mountains. An MCS (Mesoscale Convective System) may even develop overnight over Nebraska, which would promote large hail and damaging winds.
Storms will also form beginning in the evening across parts of the northern Plains and Minnesota as the low-level jet increases. As these storms initialize, some may turn into a supercell thunderstorm. Based on the turn in wind direction by height, there will be the chance for a tornado or two to form, but that chance is very low. Instead, damaging winds and large hail will be the main threats posed by these storms overnight.
Storms will also form across eastern Montana, evolving from scattered storms in the late-afternoon into a more widespread area of rain and thunderstorms overnight. These will have to be watched Tuesday morning as it may track into the western region of the Dakotas. Scattered storms are also expected to linger across northern Minnesota and into the Upper Peninsula of Michigan during the first half of the day Tuesday. That likely MCS over Nebraska will weaken by sunrise, but rain and gusty winds will still be possible in eastern Nebraska into western Iowa and northwestern Missouri for the first few hours of Tuesday.
Heavy rain will also be associated with some of these storms. Localized flash flooding will be possible as over two inches of rain comes down in some towns.