Subie Loss of coolant issues

Son-in-Law's 2010 Subaru Forester with the 2.5 Turbo (EJ25 i think), is loosing coolant.  The car has about 110,000 miles.  I know Subaru and coolant issues equals head gaskets but I am hoping that maybe there could be something else wrong.  He says he is going through about 16 ounces of coolant (water at this point) every 50 miles or so.  Car is running fine with no check engine lights, but he says he gets a flashing red light, which i assume is temperature idiot light after the car has been running for a long while.  There is no coolant in the oil, nor are there any puddles or indication of water leaking anywhere.  He says he has not seen any steam out the exhaust.  He thought he might have seen a slight oil residue in the coolant overflow tank, but there is no brown baby-poo under radiator cap.  I really don't want to have to drop the motor out of this car, I am hoping against hope there is another fix.  Any chance a cracked intercooler??  Thanks in advance for the advice.

I hope it could be something else other than head gasket but remember stereotypes are still rooted in some truth.  It is generally the truth of a few then cast wrongly as a truth about many/all.  But, if I was a gambling man, 2.5t Subaru loosing coolant with no obvious leaks does sound like HG. 

Coolant pressure test or leak down test is likely in your future.   

I am going to try a coolant pressure test tonight and hope for the best.

I believe Subies can leak coolant to the exterior at the head gasket.  Check for signs of coolant leakage at the head gasket.

While I'd bet money it's the head gasket, I've known radiators to give up after that age and mileage. 

Try looking at the exhaust gas with a bright flashlight at night, it's much easier to see if small amounts of coolant are being burned off this way.

To the pressure test I would add one of those tests that look for combustion gases in the coolant. You can rent them at the autoparts store or buy on Amazon for $40. They look like this:

Subaru has had head gasket issues for many years across both turbo and NA motors.  We lost one in our '92 SVX in 2001.  As stated they fail internally and externally and then can overheat potentially making the damage worse.  Our SVX overheated multiple times due to lost coolant though on tear down I saw no warp on the head surface just a delaminated gasket.  Ours leaked internally and was caught with exhaust gas in coolant test.  

Check the water pump too. It could be dribbling out the weep hole while running, but not leaking when parked like most other leaks. The turbo EJ25's use a much better head gasket and failure is not more common on that engine than your average engine. Not bad to check, but when Subaru switches to electric cars, people will still say they have head gasket problems.