Strong radiational cooling — clear skies, calm winds — has produced a morning with widespread temperatures in the teens this morning across Southwest Virginia and even a few single-digit readings in outlying areas. Roanoke’s official low was 20, meaning the Star City has yet to have a low in the teens all winter. It was the seventh morning this month Blacksburg fell into the teens — that seems a bit odd in such a mild January running 2 degrees above normal at Blacksburg and 4 degrees above normal at Roanoke.
A weak disturbance passing tonight may kick up a few rain and snow showers, mostly in West Virginia’s Greenbrier Valley along the I-64 corridor into Virginia and northward. Don’t expect much. More rain will arrive Friday night into Saturday with a new cold front — of Pacific origin, not Arctic. A little sleet or ice would not be out of the question on the front of that in outlying areas mainly north and northwest of Roanoke, but even that is doubtful.
Speaking of doubt, we’ve talked about the possibility of a sharp warmup for several days next week, with widespread 60s and maybe a 70-degree reading or two possible. There are some new reasons to doubt whether or not a warmup of that caliber will occur. The first is the potential for high pressure to the northeast to wedge southward east of the Appalachians. We’re not talking a cold enough air mass for wintry precipitation, just cool enough to keep highs more in the 40s and 50s than 60s. The second is that this weekend’s front may stall just south of us, providing a path for occasional waves of low-pressure to throw rain and clouds on us. (Both the wedging high to the north and the stalling front can be seen on this projected Sunday weather map, courtesy of the Hydrometeorological Prediction Center.) The third is that a cold front at midweek may shunt any really strong warmup before it gets much of a chance to get going. As of now, Monday appears to be the warmest day, with some southerly or southwesterly flow ahead of one of the waves of low pressure, and 60s may yet be possible on that day. I was fully expecting a 70-degree reading or two by Tuesday, but that seems unlikely as of now. Winter storms that don’t materialize are often called “busts” by winter fans — perhaps this time a springlike warmup will be a “bust,” although temperatures will still likely be above normal most of the time in the next week to 10 days.
It’s a complicated push and pull between air masses that, in the short term, probably won’t please spring lovers a lot and almost certainly won’t please snow lovers. As the jet stream seems to be loosening near the North Pole to allow more cold air southward (the shift from a strongly positive Arctic Oscillation phase to more neutral or possibly negative), I think it’s likely February is headed to being the coldest of the three winter months relative to normal — but that in itself is not saying a lot, seeing how mild December and January have been. We’ll see if patterns over the northern Atlantic and northern Pacific will alter to allow more true Arctic air southward for longer periods of time, or if they’ll stand pat and leave us with middling temperatures for much of February like we’re likely to see the next several days.