In a rather complicated weather scenario Saturday through Sunday, we will pick up some accumulating snow, mainly just off to the north of BWI. The first flakes will probably start as early as 5 or 6 p.m. at BWI as the broad weak low over the western Great Lakes Saturday morning remains a broad and ill-defined surface low that tracks somewhere near Lake Ontario. This weak low is supported by energy to the north embedded within an overall deepening trough across the Great Lakes. There will also be a vigorous bundle of energy coming through the upper level trough that tracks to near the coast of North Carolina Sunday morning and spawns low pressure over the Atlantic that will be strengthening and moving northward toward Nova Scotia late Sunday. This storm will not have a direct impact on our weather. The entire negatively tilted upper level trough will be swinging up across our area Sunday evening.
So Saturday, with the forcing (mainly from warm advection with the weak, broad low headed to the north, but also some forcing from overall deepening trough) we probably pick up at least several hours of snow north of BWI that brings an inch or so. Baltimore will be near the edge of the steadier snow versus just flurries and for now we think a covering of snow is the best way to go in city and areas just south. We’ll have to keep an eye on this. Farther south than that, it will be just a few flurries. The general upper level trough and lingering low level moisture can result in flurries in spots Sunday, but there may also be breaks of sun that help temperatures get up near 40.
As the entire negatively tilted upper level trough swings across the area late Sunday afternoon or early evening we will have a shot at a snow shower that could potentially bring some spots a slippery coating. With the trough axis swinging north and east we should be dry later Sunday night.