This short video from Profoto shows how shooting with high-speed sync flashes in daylight can help bring back details in the sky. The advantage of high-speed sync is that you can shoot at much higher shutter speeds than the x-sync rating of your camera. Most systems allow you to go up to 1/8000s, which means you can bring ambient light down without needing a ton of light from your flash.
In this case, they used a single B2 head in a softbox to balance the flash and ambient light. While the Profoto kits can be very expensive, the same effect can be achieved using smaller and more affordable speedlights. If name brand speedlight kits are still too expensive, third-party speedlights are available with the high-speed sync feature for less than $100.
