One cold front is pushing through this evening, but a secondary cold front arriving Saturday will be the leading edge of some colder Canadian air. By Monday morning, lows will be below freezing in most of Southwest Virginia. A few showers can’t be ruled out with the secondary front’s arrival late Saturday, but it appears the weekend will be mostly dry with seasonable temperatures, breezy at times.
September temperatures averaged very near normal in Southwest Virginia and October has been about a degree and a half above normal. It appears the third month of meteorological autumn, November, is likely to tilt on the warm side, and maybe considerably so. The weather pattern setting up features teleconnections that are opposite of those that would be expected for colder weather. The Arctic Oscillation is in a strong positive phase, meaning low-pressure spinning near the North Pole isn’t letting much Arctic air very far south. The North Atlantic Oscillation is in a less extreme positive phase, which means there isn’t high pressure blocking over the Greenland to trap cold air masses over eastern North America. And the Pacific-North America pattern, which edged into a positive phase that drove Arctic air southward sharply for a brief spell a week ago, is now in a negative phase,which means that low pressure troughing over the western U.S. is leading to strong westerlies flowing over the U.S., inhibiting Arctic air masses from slipping southward and keeping milder systems moving at a brisk pace. Long-range forecast guidance suggests that high pressure will park over or near the Southeast U.S. much of the next two weeks, keeping warmer than normal temperatures most days over a large chunk of the southern, central and eastern U.S. The Climate Prediction Center shows the orange and red colors, which means a tilt of odds toward warmer than normal temperatures, on both its 6-10-day and 8-14-day forecasts issued Friday. What this all means is that we will continue to have periods of gradual warming, maybe a couple of sharply warm days here and there, followed by quick moving cold fronts of mainly Pacific origin that knock temperatures back briefly before the warming begins again. The next front looks to arrive on Friday, similar to this week’s timing.