We present the NwsAlarm, a Java-based utility that enables users to monitor performance levels of any resource being monitored by the Network Weather Service. The NwsAlarm is invoked by a user without special privileges with a simple click on a web page link. More importantly, the NwsAlarm allows any user of the NwsAlarm to register and set expected performance levels. When performance levels fall below these thresholds, the registered administrators are immediately notified via email. The NwsAlarm uses prediction of performance measurements to filter false alarm values. We exemplify the importance of and accuracy achieved by the NwsAlarm with real examples of performance degradation caused by routing table changes and loss of service on the Abilene, Internet-2 research network used for experimentation with evolving Grid software technology. On average, 92% fewer false alarms are raised by the NwsAlarm than if raw measurements are used.