The tanks are staged and ready to roll. Fencing and barriers are up. Protective metal plating has been laid out on Washington's streets. And more than 6,000 troops are poised to march near the National Mall to honor the Army’s 250th anniversary on Saturday, which happens to be President Donald Trump's 79th birthday. With preparations well in hand, one big unknown is the weather. Rain is in the forecast, so there is a chance the parade could be interrupted by thunderstorms. White House spokeswoman Anna Kelly said Thursday that rain or shine the parade will go on. But it could be delayed if there is lightning. MORE: https://www.wthr.com/article/news/nation-world/what-to-expect-army-parade-trumps-birthday/507-d7d6c49d-7906-43fb-825a-bb7603e90548