A ceiling is the lowest cloud layer either classified as broken (5/8 cloud coverage or more) or overcast (8/8 coverage). Broken @ 3,500 and 7,000 means Langley tower observed layers (bases) of this coverage at those altitudes. Just as Rhino pointed out, Thunderbird Control (#7, #11 and supporting staff at the comm cart) was talking to Langley Tower for this info.
Right before the Hi-Lo Hit they changed to a Low Show profile which is why the Five Card was never flown. Notice how the Hi-Lo Hit became the
Hi-Lo Hit with a Left Turnout, then you can hear each Thunderbird acknowledge;
"Low Show, Low Show 2, 3, 4, 5, 6".
#7 will talk to the Boss during the show and keep him advised of any safety concerns, weather as well as real-time feedback on hits and timing. He also records notes for the debrief, including grades on narration and timing with the music in addition to the flying itself which is obviously much more comprehensive.
The Thunderbirds practice three show profiles. The High-, Low-, and Flat Show (all based on the High Show) and each pilot knows exactly backwards and forwards where to pick up a profile when the weather dictates a change from the High Show. Also, should one Solo be missing, there's a 5-Ship show profile for the remaining Solo and typically if the Diamond is missing a pilot, the Solo on that wing will take the spot during the Delta with the other Solo completing a Stinger formation instead. Unlike the Blue Angels, however, the Thunderbirds do not move their Slot pilot out on the wing to fly a three ship Wedge. When the left or right wingman is missing, the position is emtpy... a.k.a. the "Dorrito" formation.
Hope that helps shed more light on the complexity of their show somewhat!
Im interested, what they were talking about and what kind of work is on background during a flightshow. 
