Saturday was one of those days that worked out perfectly to maximize the warmth. The first batch of showers blew through quickly near sunrise, and the air dried out quickly amid southwest winds and sunshine. Roanoke hit 77 and Blacksburg topped out at 70. Lynchburg soared all the way to 80. Then, the next thin line of showers and storms didn’t arrive until very late in the afternoon. It was an amazing day for the St. Patrick’s Day festivities in downtown Roanoke … but judging by what is ahead, quite likely the warmest day we’ll see this month of March.
From Sunday into early Monday, a wedge of colder air will be working down the eastern side of the mountains — the pattern of it shows up pretty well in this map of projected lows for Monday morning. As you can see, the low is expected to be 34 at Roanoke, with darker blues just north and west. With moisture streaming in as multiple disturbances approach (and, ultimately, a stronger low moving through the Ohio Valley), there will be periods of rain Sunday and Sunday night As temperatures gradually push downward into the 30s overnight Sunday into early Monday, the threat of mixed precipitation — snow, sleet and some freezing rain — will increase from north to south and from higher elevations to lower elevations. As you know if you’ve followed previous wedge situations, pinpointing when temperatures reach a certain point at a given location, how low they get and how long they stay that way is often very imprecise. Suffice it to say for now, expect the possibility of some slushy patches late Sunday night and Monday morning, mainly north and west of Roanoke (including most of the New River Valley), and at elevations above 2,500 feet or so. The 1,200 to 2,500 foot elevations in and around the Roanoke Valley and southward down the Blue Ridge, may be on the bubble between cold rain and a wintry mix. Farther north, from Augusta and Highland counties northward, winter storm watches are out, with elevations above 1,500 feet in those areas expected to have the greatest chance of heavy snow and sleet. By later Monday, southwesterly winds from the low passing northwest of us are expected to scour out enough of the cold air to allow all precipitation to return to rain in Southwest Virginia. Being mid-March, the chances of a stubborn below-freezing wedge hanging on all day as sometimes happens are much less than they would have been a month or two ago, but areas that get snow/sleet accumulation close to I-64 may hang close to freezing much of the day.
Long-term, high pressure blocking in the high latitudes near Greenland and the North Pole is expected to force cold air southward into the central and eastern U.S. much of the next two weeks. Late in this coming week, there is a storm system moving off the Pacific that will cross the U.S. Forecast models, as typical, are varying on its track, from suppressed into the Gulf of Mexico to much farther north. There is a significant chance that at least some moisture from this storm will reach Southwest Virginia, and also a good chance that if it does, it will be cold enough for at least some of it to be snow, despite the calendar by then clearing reading “spring.”