If you can go to work, you should. If you can't go to work safely, you shouldn't. Most stores I know of do not bother with coaching a due to weather since a lot of people will be calling out. Even with documented issues, you shouldn't make a habit of calling out.
Medical issues are something that the company can work with you to reasonably accommodate for, but that does not mean that the company has to bend over backwards to do whatever they can for you. That would not be reasonable. If you need to miss work every now and again for documented medical issues, then they should be willing to work with you on your schedule. If your medical issues keep you from coming to work as scheduled on a regular basis, then you are not being reasonable by expecting them to work with you on it.
I know nothing of your situation, so take what I say with a grain of salt, but medical issues are not necessarily a protection for poor performance or poor attendance. I recently went through the process of terminating a TM due to a combination of both. Each time we had a conversation about their performance or attendance, the TM would remind me that they are on different medications or are talking to their therapist about things. They had talked to HR out their issues as well. We worked with them for nearly a year with the same issues. It finally came to the point where it didn't matter anymore. Everyone has issues outside of work be they mental, emotional, physical, medical, whatever. Companies should be reasonably accommodating. But when your issues/condition negatively impact your ability to fulfill the demands of your job, even with reasonable accommodations, then either party has every right to terminate employment.
Let me just add, that poor performance due to a medical issue can usually be reasonably accommodated fairly easy. Poor attendance due to a medical issue is a bit harder to reasonably accommodate. If you need medical leave, you are protected under FMLA. If you need certain days off for treatment, that can be done. If you call out fairly often with no rhyme or reason due to a medical issue, then that can not really be reasonably accommodated. Sporadic attendance negatively impacts the business in a manner that is not within the realm of reasonable.