Low clouds have overspread the region as easterly winds bank moisture against our mountains. The result will be cloudy, foggy, drizzly weather to start Sunday, especially along the Blue Ridge and eastward. The question that hangs over Sunday is how long this “wedge” of cooler air will hold firm. In northern Virginia and vicinity, it held all day on Saturday — all three airports that serve Washington D.C. (Dulles, Reagan National and BWI) set record cool highs for July 21 in the upper 60s and lower 70s. With high pressure moving offshore to the northeast and a cold front washing out to the south, each allowing a more southerly wind by afternoon, it’s likely the wedge will break and the sun will burn through to lift our mercury into the 80s, as shown at left. But these cool-air damming situations sometimes have a way of hanging on a little longer than expected. If that happens, it might have a hard time making 80.
Whatever the outcome of Sunday’s temperature, the week ahead on the whole looks like more of what we’ve seen lately. We’ll be east of the main core of the heat dome, so triple-digit highs are not likely, but we’re cut off from cool, dry air from Canada, too. So expect lots of highs in the 80s to lower 90s, scattered afternoon showers and storms, and perhaps on a day or two a little bit more organized storminess with disturbances and/or fronts diving southeastward out of the Upper Midwest around the heat dome high. No general rains are expected, but a few slivers of dry Southwest Virginia soil will get a brief soaking most days this week.