rfProbeThresholdWarningLimit — Multiple manufacturers; see the original MIB MIB copies (LibreNMS/Observium Community)
Warning limit for the RF control (-20.0 ... 0.0). For reflected probes: Warning limit for the reflection control. This limit is added to the fault limit to generate the real warning limit; e.g. the fault limit is -17.0dB and the warning limit is -3.0dB, so the warning is active on a reflected power higher than -20.0 dB.