The coming weekend (Sep 12-13) will be another challenge for the weather forecast world. A deep upper low is forecast by three different medium range (3-5 day) models to carve itself out of the jet stream (see map).
It is then expected to move southward into the central Plains. The makes a cold frontal passage quite likely by Saturday. Storms will probably form ahead of the front Friday or Friday night; the position of the upper low may keep the rain chance going behind the front into Sunday as well. The steering current may “leave” this low behind, wobbling about for several days to our north. If that happens, showery weather could hang around even longer.
As we saw with the scattered storms this past weekend, the timing will no doubt change as the picture becomes clearer. Overall, I expect an unsettled and cooler weekend ahead.