Try unmanaging the device during your outage window. This should prevent alerts from triggering against that device.
For me, when upgrading the Solarwinds platform itself, I unmanage all devices I am monitoring for the entire outage window. Well before the outage, I notify all IT staff that Orion will be having an upgrade and all monitoring will be halted. My users don't receive false alerts and I can reboot as necessary without problems or pollers running in the background (nothing for them to do). There is the risk of no alert being sent during this time. However, with the systems I'm monitoring, we usually have to wait only 2 minutes for a user to call when something goes wrong (poorman's alerting ).