How do I address the situation where my objectives are unlikely going to be met due to reasons beyond my control?

The AJC also encourages you to have a timely and frank discussion with your supervisor (to be documented) regarding any and all instances that have essentially impaired or are likely to impair your ability to meet certain objectives, so that you may formally request a revision to your performance objectives in accordance with the principles set out in the Manager's and Supervisor's Guide.