NEXRAD is so bad, it rarely picks up the lighter amounts & sometimes picks up non existent amounts. It's always delayed by 5 minutes. The lion kingdom still has most of the parts required for 2.4Ghz radar. It would be short range & low power. NEXRAD goes at 2.8Ghz. Theoretically, common 2.4Ghz wifi can detect rain at a short range.
NEXRAD also scans 360 degrees when all you really need is the direction the rain is coming from.