The worker-side habit this site exists for: US mass layoffs above state thresholds are filed publicly weeks before the all-hands. This week's sweep of state WARN databases found two filings from clinical research employers, both listing effective dates about six weeks out. Names and links in the trade daily; the short version is that both are concentrated in one functional area rather than across the board.
Everything here is from public filings. Discussion welcome; firsthand accounts belong to the people who have them.