If you are looking to run 100% locally with WeatherFlow Tempest you need to collect the UDP broadcast messages from the Tempest and then process them. There is a few downsides is that you lose some of the error processing that WeatherFlow does in the cloud such as Raincheck.
One other downside is you need a external app to collect the UDP since Hubitat doesn't do UDP collection. I am using WeeWx to collect the packets and then re-publishing them as MQTT which Hubitat does handle. Here is a link to my framework device that can be used to bring in MQTT Weatherflow data:
