Severe weather, heavy rain likely Monday
As an expansive, powerful upper level low will shift eastward from the Great Lakes toward parts of the Ohio Valley late this weekend into early next week. Immediately, the southerly flow ahead of it — and the nature of the upper level low shifting so far south this time of year — caught forecasters eye for severe weather potential in the Northeast US. The combination of warm, southerly flow ahead of the approaching upper level low will at least support the potential for heavy rain, while the severe weather setup has become more complicated.
Sunday evening, the first “threat” for thunderstorms will develop over Pennsylvania and Western New York state, where lift for thunderstorm development and instability will support severe storm potential. These storms will move eastward toward parts of our area later tonight, but are expected to weaken over time as they lose support for organization. On Monday, however, things will change — as southerly flow strengthens in our area, shear aloft increases, and lift develops during the afternoon to aid in the development of thunderstorms. Figure 1 shows the approaching upper level system.
Figure 1 – NAM model showing the upper level system shifting toward the area on Monday.