April 2025 KY-OH-WV-VA Hailstorm

On April 14, 2025, a severe thunderstorm passed through Kentucky, Ohio, West Virginia and Virginia bringing localized hail and wind damage to the region's forest. From NOAA's radar and field reports of hail, we have a pretty good ideal where to look for potential impacts to forest, but those data show where impacts are possible, not where they actually occurred. Change-over-time analysis that uses satellite remote sensing provides a powerful way to locate and quantify impacts. However, a major challenge for mapping impacts in the eastern US during spring is that it is hard to define "normal", given that the deciduous forest is greening up. Spring hailstorms don't damage foliage that has not yet emerged from a tree's buds. Instead, repeated observations of hail impacts have shown that large hail damages fine branches and branch tips that includes those buds. Buds are set after the prior growing season, so once damaged, it can be hard for a tree's canopy to respond to that loss. From the ground and sky above, this effectively means a delay in green up compared to surrounding areas that had no hail damage.  These slides show that sequence of impact using HiForm change imagery and higher resolution daily Planet imagery.