How to Keep MBP Connected to Wi-Fi Without Internet?

Problem: MacBook Pro connects and disconnects from Wi-Fi during service provider outage. I use it as a server when I work from home. My ISP has reported an outage so WAN is out but LAN should work?

Desired Outcome: Keep MBP connected to Wi-Fi so I can continue to connect to it locally from my desktop device.

Hard to Google this without getting results of people being able to connect to wifi but not the internet at large.