Sunday's Rare Celestial Event: Will Forecast Hamper Your View of Supermoon, Full Moon and Lunar Eclipse? [includes a map of rain and clouds superimposed over the United States].
I do wish they'd just dispense with this supermoon business, as the perfectly decent scientific term is perigee. The sad thing is I had to link to the Supermoon article at Wikipedia, as Perigee redirects to Apogee, which is the term for the furthest the moon is in its orbit from planet Earth. Oh, well. Here's hoping we get to see it clearly tomorrow!