Just as Berkshire Hathaway Inc.’s investors may be worrying that the stock’s rally off its August lows has run out of steam, a bullish chart pattern appeared Tuesday to suggest that Chief Executive Warren Buffett is set for a warm Wall Street send-off.

For the first time in nearly three years, Berkshire Hathaway’s

BRK.B 50-day moving average (50-DMA) — a metric widely used as a short-term trend tracker — crossed above its 200-day moving average (200-DMA), which is seen as a dividing line between long-term uptrends and downtrends.