UPDATE 6 AM, 8/19: Periods of rain today and Monday; cooler high temperatures this week may push 2012 summer out of 10 hottest list
UPDATE 6 AM, 8/19: Some heavy rain showers have developed this Sunday morning in the Roanoke and New River valleys and nearby areas as a wave of low pressure along the front has swept thick moisture atop a somewhat cooler air mass sliding in from the north and northeast. Additional showers are possible through the day across Southwest and Southside Virginia as the wave moves by. High temperatures will be considerably lower in areas that get significant rain. END UPDATE
There will undoubtedly be plenty of folks who remember 2012 as one of the hottest summers because of that torrid June 28-July 9 stretch, when Roanoke topped 100 four times and every day but two among those 12 90-plus days also topped 95. But the climate records for this summer, based on averages over three months, are not going to corroborate those memories. The list of the 10 hottest summers based on average temperatures for Roanoke is topped by the last two summers and 2007, impressive and indeed anomalous that 3 of the hottest summers should occur within the most recent 5-year span. Beyond that are a scattering of years from 1934 to 1987, with three years in the 1950s on the list. (NOTE: 1930 does not appear at all because of some missing dates. Considering it had 21 100-plus days, by far the most, it would most likely be somewhere near the top if records were complete). If summer 2012 ended Saturday, its 76.7 average would put it in a 4-way tie for 5th on the list. But if the National Weather Service projected temperatures for the next week are accurate (they won’t be exactly, of course, but could be close), the summer average will fall off to 76.2 and drop out of the top 10, needing a steep last-week rebound to regain a top 10 spot. 2012 will likely finish among the top fifth of summers for average warmth, but it will not be a record breaker, because of cool to normal temperatures the first 3 weeks of June and again in much of August. Heat in 2012 has been a sprint; it was a marathon in the past 2 summers.
In a few months, news that a recently passed cold front is developing a wave of low pressure (Sunday evening projected weather map linked) that will throw moisture back over will be greeted with intense interest from snow lovers . In August, it’s kind of blah. It may provide some showers to folks needing rain, especially Sunday night and early Monday, but it appears the heaviest rain will generally stay south and east of Southwest Virginia. The extra humidity and clouds are going to stymie what could have been a couple of really good nights of radiational cooling, too — instead of widespread 50s and maybe a few 40s, lows will hang pretty close to normal, upper 50s to mid 60s, for Sunday and Monday mornings. But highs, which sunshine boosted to near normal levels today in the upper 70s to mid 80s across the region, may drop back a few or even several degrees in the 70s (some upper 60s possible on Monday if it gets really socked in by rain and clouds ). The temperature regime this week will remain pretty stable, with upper 50s/low 60s common for lows and upper 70s/low 80s common for highs through most of the week, maybe a few degrees cooler Tuesday or Wednesday morning if a reinforcing shot of Canadian air can find a calm, clear night.
A long way out, we may need to keep an eye on the tropical disturbance in the eastern Atlantic or possibly the one just now coming off Africa, as forecast models are rather consistent in bringing a tropical cyclone into the western Atlantic near Aug. 30. It’s much too early to nail down specifics on path or strength this far out, but it tis the season for this sort of thing, and the pattern may become favorable during that window.