The next few days are going to be quite unsettled. Rounds of heavy rainfall could produce flooding in the mountains first, then down into the remainder of the forecast area. This is not directly related to #Isaias either. A cold front will arrive into the mountains Sunday Afternoon. This front is forecast to stall along the Blue Ridge and only slowly make its way East through the area by Tuesday Morning as it chases Isaias off to the Northeast.
Now, this will not be an all day washout by any of the three days. Thunderstorms will develop along the mountains first Sunday Afternoon. Those individual cells will track Northeast across the mountains. We will like se a training type scenario develop in a few areas of the mountains, where thunderstorms run over the same areas time and time again because the frontal boundary is forecast to stall. It could take until well up into the evening for thunderstorms to reach the eastern slopes as the front drifts slowly East.
Flow will become Southeasterly Sunday Night into Monday Morning. Moisture arriving ahead of Isaias will lead to tropical downpours as upslope showers and storms develop. These downpours will develop over the Upstate of SC and the Piedmont of NC Sunday Night and track Northwest into the foothills predawn Monday Morning. As these torrential downpours move northwest they will be enhanced when they interact with the stalled front. Topographic lift will also enhance rain rates along and near the eastern slopes.
While Monday will be quite wet with periods of rain there could be a few areas of brief sun too. So it will not rain the entire time. When it does rain it will be torrential and there could be a few stronger storms as well. By Tuesday Morning the front will sweep East ushering drier air into the region and thus ending the rain. A few more storms could develop on Tuesday Afternoon again though.
Winds will be gusty at 5-15mph but not related to the tropical cyclone. Winds will increase due to the pressure gradient between the tropical cyclone and high pressure.
Rainfall totals across the mountains, the easterly slopes, and the western foothills should be generally between 2 - 3 inches. Across the southern and eastern foothills rainfall totals should end up between 1 - 2 inches. Of course there will be locally higher amounts, especially along the Blue Ridge and where thunderstorms train over the same areas time and time again.