By Justin Drabick

PHILADELPHIA (CBS) — The weather pattern has remained cold over the past week — and a good set up for a late season winter storm.

A storm system across the northern Plains and another across Oklahoma Monday night will merge together for a large and strong storm across the mid-Atlantic on Wednesday and intensify as it moves off of the coast.

As of Monday evening, the main storm has not developed yet, so the exact track and timing of the storm is uncertain. That is what will determine what type and how much precipitation we will see. The bullseye of moisture looks to remain well to the southwest across West Virginia, Virginia, & western Maryland, making this the biggest storm of the winter for the mid-Atlantic.

As of now, expect rain to arrive at or before daybreak on Wednesday, possibly starting as snow west of Philly. The rain will eventually change over to snow from west to east. Temperatures will be above freezing throughout the day, so even though temperatures aloft will support snow, temperatures near the surface will be borderline for snow. Where it does snow, any accumulations should remain on grassy areas and non-paved surfaces. Given that it is March, the sun’s rays can still penetrate the clouds and warm paved surfaces a bit. After sunset, colder air will return, and that will be the best chance for snow accumulations of a few inches, with higher amounts west of Philly. A winter storm watch is in effect for Chester County, PA and Cecil County, MD.

Another component of the storm will be the wind. As the storm intensifies on Wednesday, strong east to northeast winds will develop. This onshore wind flow will start to pile up water along the coast on Wednesday into Thursday. A coastal flood watch is in effect for Delaware and New Jersey, with possible moderate coastal flooding from Wednesday afternoon through Thursday morning. Winds may gust to 50 mph along the coastline on Wednesday and Wednesday night.