Haven’t seen this in a while in our area. We have been touching up seed jobs this week. Haven’t had to break up the soil in most lawns because the freezing and thawing cycles over the past few weeks have done it for us. Basically, ice crystals form below soil surface and grow towards the direction of heat loss, and it almost looks like grub damage or skunk damage when they dig for grubs. The only real negative is immature seedlings from the fall seeding can be uprooted and killed. I will post some pictures tomorrow of a few dead seedlings. The good news is heaving soils make a decent seed bed! Seed we plant now will usually germinate by early March, but then again in TN it could be snowing or 85 in March! We will wait until new seedlings emerge before applying first application of preemergent on reseeded spots.