UPDATE 12:30 AM, 3/20: I’ll let this ride another day. Highs in the 70s, maybe some low 80s. Scattered showers and storms possible. After hitting 78 to set a record high on Monday, Blacksburg’s record March 20 high of 75 from 1968 may also be overtaken (if early showers don’t happen to stop it). Roanoke’s record of 83 from 1945 and 1968 probably stands. END UPDATE
UPDATE 11:50 AM, 3/19: The area of showers and storms affecting much of the region this morning has mostly dissipated. With the sun popping out, widespread highs in the 70s appear likely. Afternoon heating combined with thick moisture and an upper-level impulse sliding southeast from the Ohio Valley may fire a few scattered storms during the afternoon and early evening. END UPDATE
UPDATE 8:45 AM, 3/19: We’re starting off on the damp to downright soggy side this morning. Not only have fog and low clouds settled in to much of Southwest Virginia, but an area of showers and storms with some heavy rain has been affecting much of the area north and east of Roanoke. That’s a flip from much of the past several days when the action was mostly south and west of Roanoke. Some of the cells developing on the back end of the system in West Virginia may drag through the Roanoke and New River valleys later this morning. Click here for latest National Weather Service-Blacksburg radar. Temperatures this morning are already near or somewhat below the normal high temperatures for mid-March in the 50s (57 at Roanoke, for example, with a normal high of 59 — and normal low of 38) so the “much warmer than normal” part is on track again despite the rain and fog END UPDATE
Wednesday’s toasty highs in the mid 70s to low 80s could have easily been the start of a long period of similar high temperatures. But the last four days, instead, have had interference from upper-level disturbances from the west, a backdoor cold front from the northeast and a weak flow of cooler, moist air off the Atlantic. The result has been hard-to-predict periods of clouds and showers and rather erratic daily high temperatures. Highs Thursday through Sunday were 58, 69, 72 and 64 at Blacksburg and 69, 73, 75 and 66 at Roanoke – all above normal, though none of them as extreme as they could have been. The leftover moisture from the past few days, some more disturbances moving in from the Ohio Valley and a persistent weak low hanging around the Outer Banks may trigger additional showers and storms the next few days. (Amounts up to a half-inch are projected the next 3 days in our area — also note on this map the 5-8 inches projected in parts of Texas, Oklahoma and Arkansas with a major, slow-moving storm system there that will likely also trigger plenty of severe storms and some tornadoes.) This will again make projecting daily highs and rainfall chances a bit difficult — clouds and showers at any location on a given day can shave several degrees of highs, but then again, warmer highs at a given location can create more instability for afternoon showers and storms to develop. We are still under the effects of the warm dome of high pressure that has dominated the central and eastern U.S., so any day this week will easily reach the 70s and possibly some low 80s IF there is sufficient sunshine. That should be the general expectation each day through at least Friday — highs mostly in the 70s, maybe some low 80s, with some showers and storms possible any of those days to shave some degrees off the daily temperatures. It’s a summerlike pattern that is likely to continue through this week, with at least some signs it may change to a bit of a cooler springlike pattern by the weekend or early next week following a significant cold front passage.