Discussion
Currently, broad ridging is centered to the west with troughing in the northeastern U.S. Drier air remains centered to the north and east with a 5,950m high in place. This will be the focus for isolated to scattered showers and storms already developing. Luckily, these areas are less saturated than places to the north, giving more opportunity for drying out from recent rain. By tomorrow, the 500mb high will shift off to the east, allowing better moisture to expand northward. This will also lead to an expansion of shower and thunderstorm coverage during the afternoon and early evening hours. With weak flow aloft, the storms will continue to depend on instability with MLCAPE values of 2,000 J/kg or great, meaning some stronger storms are certainly possible. The CAMs do differ on how much overall coverage there is, which would also impact the flooding threat as well. At a minimum, isolated flooding will also be possible.
By Saturday, a shortwave will swing down from the northern Great Plains into the Great Lakes with a surface low tracking along southern Canada. This will lead to some height rises and potentially higher lapse rates, supportive of more widespread convection, in addition to surface troughing. A few strong to marginally severe storms are possible capable of damaging winds, depending on the extent of surface heating and destabilization. Activity could also continue through the evening as the frontal boundary associated with the surface low progresses southward. This will keep elevated chances for convection on Sunday, potentially less intense if convection and clouds linger from Saturday.
By Monday, the front will have moved into the region, ushering in drier air. An upper high will also expand to our west, leading to height rises and an increase in temperatures. By Tuesday to Wednesday, another system will track along southern Canada, pulling the boundary back further north, allowing for moisture return. The evolution of the pattern remains uncertain, but more widespread convection could return.