A discernable pattern means that there is a clear and noticeable arrangement or sequence of something. It implies that the elements or behaviors can be recognized and understood because they are repeated or have a predictable order. Full definition
And scattered around them are actors who've been in one or more of the many other MCU films, arranged with no discernable pattern whatsoever. (inverse.com)
There is no discernable pattern for when the alarm goes off - it has happened in... (mechanics.stackexchange.com)
(b) You should schedule follow - up tests on dates of your own choosing, but you must ensure that the tests are unannounced with no discernable pattern as to their timing, and that the employee is given no advance notice. (transportation.gov)