Severe, Reoccuring Latency Spikes

I am reaching out for any information regarding a very frustrating and recurring issue that has persisted on my network for a few months now. My internet latency increases drastically during peak evening hours, primarily making multiplayer gaming unusable at these times. This wouldn't normally be a large issue, except for the fact that the problem follows an incredibly predictable pattern. It occurs every Thursday and Saturday evening, sometimes other days of the week sporadically, starting around 6:30-7:30 PM and lasting for several hours. 

I have tried everything I can think of. Since my modem was going on 7 years old, I thought that might've be the culprit. But after replacing the modem with a Ubiquiti UCI, the issue still persists. I've gone through the usual troubleshooting of restarting the router and modem and ensuring their firmware is up to date, to no avail. This issue affects all devices on my network, both wired and wireless.

I was able to do a trace route during one of the periods of increased latency to an AWS us-west-1 server, the same AWS Region hosting the game servers that I experience the increased latency on. The first hop from my device to my router remained normal at 7ms, but as soon as it takes its first hop out of my local network the latency instantly spikes to over 115 ms, and carries that all the way to the destination server.

Given that I have replaced the modem and the issue is consistently starting as soon as the data leaves my local network, I don't believe this is anything to do with my network setup. If it is a network congestion or the over utilization of a node in Xfinity's network, I don't know why it only started a few months ago.

I would appreciate it if anybody has seen a similar issue or has advice on how to get this resolved. Thank you.