If you were wondering why you are not getting many Wireless Emergency Alerts for Flash Flood Warnings this year, earlier this year the NWS made a change to the activation criteria for FFWs, using a tiered system. The three tiers are Base, Considerable, and Catastrophic threat levels. Of the three, Base level FFWs no longer activate WEA.
Now, the NWS is proposing a tiered system for Severe Thunderstorm Warnings - Base, Considerable, and Destructive. Of the three, those in the Destructive tier will activate WEA. This can be useful for derechos, which are often more damaging than weak tornadoes.