Most teams measure forecast accuracy once, at the end of the quarter, when it matters least. Measure it early and often instead.
Save the commit every Monday. At quarter end, compare each snapshot to the closed number and plot the error over time.
Error at week four tells you how much to trust the forecast for planning. Error at week eight tells you whether there is still time to act.
If early error is high, look at categories first, then stage weights. Change one thing per quarter so you can see what helped.