@tfriess
at 15 and tall and lengthy you probably need to work on balance, indo board and Yoga
stick to the basics for weights, squats, bench press and deadlifts, these three will do more for your "core" than the 1000's of dumb exercises created for this trending phrase. For the winter stay in a 3-5 set 6-8 rep range, strength is something to build on in winter, and your not going to get bulky in that rep range, other exercises in the 3 set/15-20 rep range can be added to make a solid 3 day a week workout...
Cardio, you probably don't need it too much for actual weight loss but running is the ticket, makes you tough, there is no better cardio workout...for you, do H.I.I.T. with your running, more representative for skiing applications...
AND EAT CLEAN...all the working out in the world isn't going to do squat if you do not fuel properly...
Can be more informative and detailed if you need in regards to workout and diet, just send me a PM if interested...