A storm impacting the Ohio Valley today will move east into the Mid Atlantic tonight. Snow from this system is falling across southern Ohio at this time, and this precipitation will move eastward across southern Pennsylvania through tonight with a coating to possibly a few inches of snow possible, especially across the higher terrain.
That system will quickly move away from the area tomorrow. The flow will turn southwest ahead of our next weather maker – a clipper over the western Great Lakes. This southwesterly flow will transport milder air into the region. As the clipper moves closer to the area, showers will develop, most likely Thursday afternoon. With the milder air in place, most of this precipitation on Thursday will be in the form of rain.
A cold front will swing west to east across the area Thursday night, ushering in colder air and changing rain showers over to snow showers.
A secondary surge of colder air will arrive on Friday. The colder air will deepen with instability over the lakes increasing. Conditions will become favorable for lake effect snow to the southeast of the lakes. Some of this lake effect snow could be significant.
The cold northwesterly flow across the lakes will continue through Saturday and possibly into Sunday with favorable lake effect snow parameters persisting. High pressure will finally shut down the lake snows Saturday night or early Sunday across the western areas and later Sunday or Sunday night across the east.
Then, a complex and potentially major storm system is forecast to deepen across the Mississippi Valley on Monday and move into the Ohio Valley and eastern Great Lakes Monday night and Tuesday bringing a variety of weather to the region including the threat of rain, ice, and snow.