It’s indisputably gotten warmer over the last 30 years, with the last 10-15 years really spiking. When a degree or two is important for precip type in winter storms, that matters. Everyone in the area has gotten a few ticks warmer, but the burbs had more cushion since they’re colder to begin with. Add in some extra help from the UHI for the areas inside the beltways and it just makes marginal events into white rain or plain rain.
Unfortunately, the burbs are following along behind on warming and will also probably see marginal events slip away in the coming decades.