Western Digital Corp. slumped more than 12% in after-hours trading Wednesday following an earnings report that included a disappointing forecast for the hard-drive maker’s new fiscal year. Western Digital reported fiscal fourth-quarter earnings of $148 million, or 49 cents a share, on sales of $4.29 billion, up from $3.63 billion a year ago. After adjusting for stock-based compensation and other factors, the company reported earnings of $1.23 a share, up from 17 cents a share last year. Analysts on average expected adjusted earnings of $1.22 a share on sales of $4.36 billion. While Western Digital’s revenue was a bit light, the bigger miss was in the fiscal first-quarter forecast, which called for a year-over-year decline in sales with guidance for adjusted earnings of 45 cents to 65 cents a share on sales of $3.7 billion to $3.9 billion. Analysts on average were expecting adjusted earnings of $1.35 a share on sales of $4.36 billion. Western Digital shares have declined nearly 30% so far this year, and closed with a 0.7% decline at $44.47 Wednesday before plummeting to less than $40 in after-hours trading following the announcement. Market Pulse Stories are Rapid-fire, short news bursts on stocks and markets as they move. Visit MarketWatch.com for more information on this news.