The string of disturbances riding the jet stream will continue into this weekend. These storms, paired with moderate to high precipitable water values, will aid in the risk for flash flooding across parts of the Midwest through the Mid-Atlantic, a region that has stayed wet for most of this spring.
On Saturday, most of the activity will be focused across the Great Lakes region during the morning hours. Heavy thunderstorms have been impacting the Chicago area this morning, and these storm will slowly move off to the north and east into Lower Michigan. Showers and storms will also continue in parts of the Upper Midwest and Ohio River Valley. Into the afternoon hours, a few thunderstorms will develop across the Mid-Atlantic, especially over New Jersey and the DelMarVa. Back to the west, multiple lines of strong to severe thunderstorms are also forecast to form, one over the Ohio River Valley and a second near the Quad Cities. This second line has the highest risk for producing severe storms. Even a couple tornadoes may be produced by this potential Mesoscale Convective System, as well as damaging winds and large hail — a threat which will exist for all remaining areas. There will also be a severe weather threat in southwestern North Dakota and northeastern Wyoming. A few spotty thunderstorms are expected to develop in the afternoon, some of which may make for a damaging wind and large hail threat. Even further west, severe thunderstorms will be possible in western Montana during the afternoon and overnight hours as rounds of thunderstorms move through.
Overnight Saturday, a few storms will continue across the Mid-Atlantic while an area of scattered to widespread thunderstorm activity continues across the Ohio River Valley, especially to the north of the river. We are concerned about flash flooding, especially in the greater Quad Cities area due to the multiple rounds of heavy rainfall.
On Sunday, severe thunderstorms will be possible from the Northern Plains to the Ohio River Valley. The best risk for severe activity will be in the Dakotas, where damaging winds and large hail will be possible in some areas as well as a spotty tornado. This will come with a widespread line of thunderstorms that will move east across the region. Meanwhile, in the Midwest and Ohio River Valley, there is only a low risk for severe weather, as storm activity will be isolated in nature.
Overnight Sunday, these storms will push to the east, moving into Minnesota and Iowa. By this time, most of the storms will have weakened, but isolated parts of this line may still be strong enough to meet severe criteria. A reminder that a severe thunderstorm means that winds are of at least 58 mph or hail is of at least 1 inch in diameter.
By Monday morning, area of showers and thunderstorms will continue across the Northern Plains and Midwest, albeit in a weakened form. Flash flooding will remain a threat in some areas.