Plot a time series, but alert only on the most recent datapoint

I’m trying to plot the last 30 days of a metric which is sampled daily, and send an alert if the most recent sample has crossed a goal line. I want the alert silenced as soon as another datapoint arrives which resolves the metric.

If I use a goal-line alert, the notification to our Slack integration includes a static image of the particular chart and goal line, which is good context for the team receiving those alerts.

In forums it appears I need to limit the question to one datapoint for purposes of the goal comparison. I don’t see how to do that without also limiting the visualization?