UPDATE: 9 AM, 5/8: A large area of moderate to locally heavy rain is moving southeast from West Virginia into Southwest Virginia. That’s right, I said southeast — after two days of odd east to west/southeast to northwest motion on rain and storms we’ve returned to a “regular” direction of movement, because we’re now behind the low, now centered just north of us. This will add to rain totals and may exacerbate flooding or at least slow runoff in some areas still suffering it. Rain will obviously be more widespread in Southwest Virginia than earlier thought and likely with heavier amounts (more than a half inch), at least for some. The system is continuing to slowly unwind and drift northeast, though, and will probably be out of our hair by tomorrow. Check out local radar for the latest. END UPDATE
Cut-off upper lows die slowly. Each day, this one is becoming just a little less organized, and rainfall is becoming more sporadic and diurnal — or connected more and more to daytime heating rather than remaining organized through the night. That doesn’t mean it can’t rain at night — some showers will be ongoing at almost all hours — and it certainly doesn’t mean there won’t be some heavy rain, though it’s getting more and more localized. But just as Tuesday’s rainfall spinning around the upper low tended to be more patchy than Monday’s, Wednesday’s will likely be even a little more sporadic. The North American Model simulated radar for Wednesday afternoon at left shows a fair amount of showers, storms and rain bands blowing up with daytime heating (you can see the swirl of the upper low, expected to be centered over Virginia, sliding a bit northeast from its North Carolina position much of today.) The Weather Prediction Center projects most of the area to get a quarter to a half inch in the 24 hours through Wednesday evening – more likely, this will be an averaged-out amount rather than evenly brushed, with some spots getting more (a couple of inches would not be out of the question in a localized downour) and many getting less. The cut-off low had a cold enough center on Tuesday for some snow to reach the surface above 6,000 feet in the western North Carolina mountains, and for hail to develop in storms that typically wouldn’t be tall enough to support hail this time of year. Because of the presence of this cold air aloft, hail will be a possibility in some of the stronger storms on Wednesday.
By Thursday, the cut-off low will finally become not so cut off, pulled north and east away from us. That day could easily end up being sunny and quite warm (70s) with only minimal chances of showers and storms with some residual moisture and influence from the departing storm. A weekend cold front will bring the next organized chance of showers and thunderstorms Friday and Saturday — the kind that will move west to east, not this weird east to west we’ve been watching on radar the last couple of days. Early next week there may be a couple of frosty mornings — keep that in mind for outdoor vegetation.