The upgrade by B of A Securities to a Buy rating and the increase in price target to $78 from $62 is a strong positive signal for HF Sinclair's stock. Such analyst upgrades often lead to short-term price appreciation as they reflect improved confidence in the company's future performance and financial health. The significant jump in the price target suggests that B of A Securities sees substantial upside potential in the stock, likely based on fundamental analysis or sector trends. This can attract more investors to the stock, driving up its price in the short term.