As of 7 p.m. Tuesday the forecast called for snow to start falling by dawn, continue until the afternoon and taper off by dusk.
According to the Chester County Office of Emergency Services "A warning is issued when a hazardous weather event is occurring, imminent, or has a very high probability of occurrence."
The National Weather Service forecast for the rest of the week calls for clearing and cold, until Saturday when there's more snow in the forecast.
- Tuesday Night: Mostly clear, with a low around 18. West wind 9 to 11 mph.
- Wednesday: Increasing clouds, with a high near 31. West wind 8 to 14 mph.
- Wednesday Night: Mostly cloudy, with a low around 17. West wind 6 to 8 mph.
- Thursday: Mostly sunny, with a high near 26.
- Thursday Night: Mostly clear, with a low around 11.
- Friday: Mostly sunny, with a high near 27.
- Friday Night: Mostly cloudy, with a low around 23.
- Saturday: Rain and snow. High near 39. Chance of precipitation is 80%.