We have not seen these purple colors on us much in the past few months. Those colors on the Hydrometeorological Prediction Center forecast map denoted 1.5 inch of rain or more expected to fall in the next 5 days. While a weak low passing north of us on Christmas Eve may supply some of that (maybe snow as close as Northern Virginia), the bulk of it is expected to arrive late Christmas and especially Wednesday with a much stronger low passing to our west. There is still some chance that the initial phase of the precipitation in Southwest Virginia on Wednesday will include some freezing rain, sleet or snow, as the first waves of moisture fall into some cold air trapped near the mountains. But the latest forecast data is suggesting less cold air, more of a western track to the system, and therefore more likely a primarily rain event for Southwest Virginia. There is still time for details to change, but this does appear to be trend forecast models are moving toward, and there does not appear to be enough blocking features to our north to force this storm system farther south and east. Considering the long-term drought this region and much of the Mid-Atlantic and Southeast are suffering, Wednesday’s projected rain will be beneficial. A low track just west of the Appalachians is often a wet path for us, as it draws Gulf of Mexico moisture northward on the east side of the counterclockwise rotating low, and also pulls in some Atlantic moisture on east and southeast winds ahead of the low. What’s more, southeast winds as the low goes by to the west can squeeze more rain out, lifting dense moisture up the gradually rising slope of the western Piedmont and the much sharper rise of the Appalachians. Some details of the storm’s evolution — mainly, whether it will spawn a new low on the East Coast, or maintain an inland track toward the Great Lakes, often called a “lakes cutter” — are still unclear, but once it goes by, we will get another blast of Arctic air on northwest winds not too much different than what we just experienced. By late Wednesday or Thursday, expect some more upslope-generated snow showers in the mountains west of Roanoke with perhaps some flurries flying farther east.
Be aware if your travel plans take you west or north for Christmas, as heavy snow could affect parts or all of many states, such as Ohio, Indiana, Pennsylvania, West Virgina, Kentucky, Tennessee, Missouri and Arkansas. Severe weather with possible tornadoes may occur in parts of Alabama, Georgia, Florida and South Carolina. It’s a vigorous winter storm system with a cold and warm side. We’re likely going to be in between the extremes.
We’re in that season when there may be a new storm to watch around every corner. The next could happen around New Year’s Eve, with yet another 3-4 days later. It appears we are entering a pattern where there is cold air hanging around near or just north of us, and a more southerly course for the jet stream that would bring energetic systems across the southern half of the nation, putting almost every storm into some question as to precipitation type. Storm track and placement of features to the north that could drive cold air southward will be the key with each storm. Welcome to winter.