Do you think there's an audience for that level of analysis?
Meta,
It depends on who your audience is.
Your OP simply asked how to forecast for a bottom. I tried to give you some clues to look for but also reminded you of the clues that would indicate the opposite.
I assumed you yourself were the audience for this not so scientific forecasting.
For data strong enough to use in a typical mortgage appraisal, you will not know until you have hindsight.
But what you put on your typical mortgage appraisal is not a forecast, it is based on actual data.
For example, the charts you posted did not indicate to me that the market is no longer in decline. But say you reach a point where it does look that way. But you also know that the listing data is contaminated by the temporing factors I mentioned. You would not mark anything other than 'declining' on your appraisal. How you present your justification analysis is a seperate issue.
Just because your client will accept a report for the sole reason that a chart that seems to justify stable or increasing check boxes is not a valid reason for doing it. You, as the appraiser, have to justify it to yourself.
It is not a matter of "What can I get past the UW." It is a matter of "Have I performed competently?"
When I convince myself that my market has turned around, I don't want to have to be in the position of having to switch back and forth between trend boxes on every other report or every other month.
A validation of a trend is based on a length of time.