The threat of unemployment is on the rise again in the San Francisco Bay area. After falling for three consecutive months, the number of layoff announcements affecting Bay-area counties shot back up in May. The California Employment Development Dept. received notifications for over 4,900 permanent layoffs through the Worker Adjustment and Retraining Notification system, known as WARN. This was the second-highest monthly total of notices received in the current downturn and was an increase of more than 100% from April.