Weather overlay doesn't seem very accurate for today.

I agree with your assessment and we've initiated a discussion with the providers of this data.

Tim,

Yes. The phenomenon was caused by an offset in satellite measurements our data provider uses for estimation of cloud tops, which feeds into the algorithm used to estimate cloud ceilings. As with all meteorological modelling, it's complicated and such an offset will only happen under certain conditions. However they now have a plan to detect such conditions and correct for it, and are working on that.