CommunityCeiling Leak in 1st Floor Bathroom During Heavy Rain

Ceiling Leak in 1st Floor Bathroom During Heavy Rain

Today during a heavy rain I disovered that we had a leak.  We had a steady drip of water coming from the furrdown in the powder room.  It only lasted about 20 minutes, but it continued to rain heavily for another hour which I thought was unusual.  Not that I wanted more water in the house.  We'd love some advice on how to repair/diagnose.  Thank you!

The Money Pit Answer

Most leaks over bathrooms - even first floor bathrooms in two-story homes - are caused by one thing, and one thing only: Plumbing vent flashing. 
Pipes extending through your roof are flashed using rubber gaskets, with shingles laid overtop to create a watertight seal.  Constant sunlight exposure, though, can cause materials to deteriorate, allowing water to get in.  Once inside, the water follows that pipe through the home, to wherever it ends - which in this case, I'd wager, is your first-floor bathroom.  
Try repairing the plumbing vent flashing by sealing or replacing it and see whether the leaking stops.