This low, which will have some minor impulses and features rotating through and around it, will cause a little fluctuation in shape and orientation over the next three days. However, those differences will basically be insignificant for us, although there will be some trackable differences farther north up into New England and eastern Canada.
At the surface, we will have some version of broad low pressure from Nova Scotia to Newfoundland. Well to the west in Ontario, Canada, high pressure is nosing southward through the middle part of the United States. The resulting flow between these weather systems is the chilly to cold northwest flow across a large part of the eastern half of United States, and this set up will change very little over the next couple of days.
With the upper level trough and cyclonic flow, places like Buffalo to Pittsburgh and the mountains of western Md. and West Virginia can expect plenty of clouds and generally light flurries at times Saturday through Sunday. Areas from southeastern New York to eastern Pennsylvania and the Baltimore/D.C. area can also expect more clouds than sun with at least several hours of solid overcast skies. With the breeze being a little more active from PHL to BWI and thus more of an a down-sloping effect, there are apt to be more holes in the clouds for these areas, especially in the morning, before the instability generated by the whole upper level trough causes any sunshine to self-destruct during the midday and afternoon. In Allentown and New York City, we think any sun will be less appreciable, and there will be enough moisture and instability and also a little upper level disturbance rotating through the trough that may help to squeeze out an isolated sprinkle or flurry later Saturday. It’s nothing significant though and we just play this as a “mention” and not a “post.” There will be some spotty returns on radar, but again, much of it will not reach the ground and will not be significant. The farther north and west you go and into the mountains, the more like it will be to see some flakes.
We expect a chilly breeze and temperatures Sunday for Baltimore.
Overall, for Monday, sun will be a little more appreciable than Saturday and Sunday, but there are still apt to be intervals of clouds the farther north and east you go as the upper level trough will be slow to move away and a slice of high pressure approaches from the west.