At the countdown status briefing on 26 August NASA shuttle weather officer Kathy Winters said that on 27 August the launch team will still be dealing with afternoon storms, with the chance of "no go" for weather now at 60%. The US space agency's test director Jeff Spaulding reported that teams were also still assessing any potential effects from a lightning strike at the pad on Friday 25 August.

Atlantis STS-115w445

 Above: Atlantis is at launch pad 39B

Similar weather conditions prior to the 1 July attempted launch of Shuttle Discovey for mission STS-121 saw that lift off scrubbed for another three days, eventually launching on 4 July.  Despite the deteriorating weather Spaulding said the countdown was proceeding as scheduled. This evening at launch pad 39B the rotating service structure is scheduled to move away from the shuttle at about 2300GMT and Atlantis will stand ready for liftoff.
The 11 day mission will see the assembly of the Port3/Port4 truss to install new solar panels for the International Space Station (ISS). The mission, STS-115, will see the ISS assembly sequence restarted after the 2003 Columbia disaster that saw flights halted for two years. The launch window for Atlantis is 27 August to 7 September.