--- - |2+ Background Our understanding of suicidal ideation (SI) and its risk precursors is largely informed by studies spanning over wide time intervals (weeks, months, years). Little is known about SI as it occurs in daily lives of individuals at risk for suicide, the extent to which suicidal thoughts are dynamic over short periods of time, and the degree to which theoretically informed risk factors predict near‐term SI. Methods Thirty‐four adolescents hospitalized due to last‐month suicide attempt and/or last‐week SI (76% female; ages 13–17) responded to daily surveys sent to their cell phones for four consecutive weeks after discharge (n = 652 observations). Results There was notable variability in day‐to‐day SI, with half of ideation ratings changing at least one within‐person standard deviation from one day to the next. Results of mixed effects models revealed concurrent (same‐day), but not short‐term prospective (next‐day), associations between SI (frequency, duration, urge) and well‐established predictors (connectedness, burdensomeness, hopelessness). However, synergistic effects of low connectedness with either high burdensomeness or high hopelessness were reliably associated with more severe same‐ and next‐day suicidal ideation. Conclusions This study adds to emerging literature indicating that suicidal thoughts fluctuate considerably among individuals at risk for suicide, further extending it by focusing on adolescents in the critical posthospitalization period. Fostering high‐risk adolescents’ sense of connectedness to others may be an especially promising intervention target. Frequent assessment of SI and its predictors, independently and in combination, could help identify promising predictors of short‐term risk and meaningful intervention targets in high‐risk teens. - Journal of Child Psychology and Psychiatry, EarlyView.