From the NWS:
Saturday night through Monday... The first of two eastern Pacific systems will move into the northern Plains Sunday and upper Midwest Monday as the high amplitude ridge portion of the block gets broken down. Prefer the slightly further west combination of the 00z ECMWF and ensemble means due to the typical poorer handling of blocking patterns of the GFS. It looks like an associated surface system will gradually lift northeast over the Great Lakes and Ohio Valley next week. However, another southern system will complicate things further, namely the evolution of a complex surface pattern. In general, it looks like a warm front and dry slot may be be spreading across from the southwest on eclipse day. This should give some hope that enough clouds will scour by Monday afternoon for viewing of the eclipse. Better chances for convection will follow toward midweek as the second system gets involved. Meanwhile, southerly flow ahead of the surface will ramp up and allow for temperatures to quickly climb back to well above normal with upper 60s and lower 70s possible Monday.