UPDATE 11:20 AM, 9/24: There were several lows in the 30s and some scattered frost west of Roanoke this morning, with low 40s common in the Roanoke Valley and points south and east. Tuesday morning may be almost, but not quite, as warm, before a quick warmup takes some spots into the low 80s by Wednesday afternoon. I plan a new blog post this evening.END UPDATE
UPDATE 4:05 PM, 9/23: Frost advisory issued for Monday morning west of Roanoke, including the entire New River Valley. Scattered frost may develop, particularly in sheltered valleys, where temperatures in the 30s are expected. Widespread upper 30s to mid 40s are expected for morning lows on Monday morning across Southwest Virginia. END UPDATE
We’re finally getting to the core of the colder air that has been pouring over us from Canada behind a series of cold fronts the last couple of weeks. The front will pass through Southwest Virginia on this Saturday evening — it only triggered a narrow, broken line of showers and storms to the south and east of most of the region during the afternoon, affecting the Martinsville area for a time. Sunday morning will be cool with lots of 40s and low to mid 50s, but it’s Monday morning when we are likely to get clear and calm enough for some genuinely cold readings, with mid to upper 30s expected at many sites west of Roanoke (and some in cooler valleys elsewhere), and low to mid 40s just about everywhere else. Scattered frost will be possible, especially in the colder, sheltered valleys west of Interstate 77 (perhaps a sub-freezing low inside the “crater” at Burkes Garden?) extending into West Virginia. While Monday’s lows could be 10-12 degrees below normal, they’re not close to record-challenging — Roanoke’s 34 and Blacksburg’s 22, both from 1983, will likely stand as Sept. 24 record lows. Tuesday morning may be similarly chilly, perhaps a couple degrees warmer, as we begin a gradual warmup. Highs may not top 70, possibly even in Roanoke on Sunday, and will only gradually push into the 70s through the early part of the coming week. It appears that this particular bucket of cold air from the tundra will just about be poured out, so subsequent cold fronts over the next 7-10 days are not likely to bring as much chill. Extreme summerlike warmth is also not expected, though there are some signs of warmer high pressure building eastward over the next week or two. Overall, it appears that a long period of pleasant temperatures and mostly dry days — for better and worse — will continue across Southwest Virginia into the foreseeable future.