Congrats to KIAX for being the FTF!
After completing the Adventure Lab here, you will have the information needed to find the bonus cache. This is about 100 feet from the trail and can be safely obtained in all weather conditions, so if you find yourself doing something dangerous, you are. STOP and make sure you have the correct coordinates and you are following the hint.
Solve for N40 59.ABC W73 54.DEF