Create a breathtaking impressionistic landscape of majestic mountains during autumn. The scene should feature a winding river in the foreground, its surface reflecting the vibrant colors of the surrounding trees. The trees, adorned with fiery reds, oranges, and yellows, frame the river, creating a harmonious blend of nature's palette. Above, dramatic clouds swirl in the sky, casting shadows on the rugged mountain peaks that rise majestically in the background. The lighting is soft and diffused, typical of an autumn day, enhancing the warm tones and creating a serene yet dramatic atmosphere. The impressionistic style should be evident in the brush strokes, allowing the colors to blend seamlessly, evoking a sense of tranquility and awe in the viewer.