UPDATE 5:25 PM: Warmest morning in Roanoke history leads to 103-degree high; severe storms on the way this evening
UPDATE 5:25 PM: Roanoke’s official high through 5 p.m. was 103 degrees — the hottest day in 29 years, since it was 104-105-104 on Aug. 20-22, 1983. It’s tied for the second hottest high in June, trailing only 104 from June 30, 1936, and is the first high of 100 or higher in June since 1959. Blacksburg reached a high of 95, which is the hottest ever recorded in the month of June since records began there in 1954. Combined with very warm lows of 84 at Roanoke and 78 at Blacksburg, this is the hottest day by average temperature that either site has ever seen — but it’s possible the low temperature end of that will be affected by an area of storms moving rapidly through the Ohio Valley. Whether or not that “bow echo” storm cluster (radar image at left) moves directly through, an outflow from it may cause cooler temperatures than this morning’s lows before midnight, which would thus supplant those lows for the date. You can track it on the Radar / Future Cast at right. END UPDATE
UPDATE 3:30 PM: Roanoke has officially hit the 100-degree mark as of 3 p.m. It is the first 100 in June at Roanoke since 1959. END UPDATE
UPDATE 9:50 AM: The National Weather Service in Blacksburg has confirmed a morning low of 84 in Roanoke, which if it stands til midnight, would be the warmest low in Roanoke’s weather history by 4 degrees. However … before we etch that in stone .. the threat of evening thunderstorms appears to be on the increase, and it would probably take thunderstorm downburst winds to get it cooler than 80 by midnight. It is possible that a storm cluster may develop in the Upper Midwest/Ohio Valley today and rocket southeast, near or perhaps through Southwest Virginia. The Storm Prediction Center has placed much of our region from Roanoke northward in a slight risk of severe weather for this possible. Damaging winds would be the primary threat if this storm cluster — perhaps a “bow echo” or derecho — develops. Before any of that would occur, it’ still likely to reach or exceed 100 at Roanoke. It’s already 90 at 9 a.m. END UPDATE
This morning’s low at Roanoke Regional Airport, based on the automatic observations available on the Web site linked here, was no cooler than 82 degrees (depending on when 82 occurred — it was low in 6 hours before 2 a.m., so it may have occurred before midnight, in which case, morning low may have even been warmer). The warmest low that has ever been recorded previously at Roanoke since 1912 is 80 on four different occasions in the 1930s and 40s. In more recent times, Roanoke had a low of 79 on Aug. 9, 2007, and 78 twice last summer. If this is confirmed as official, it will stick as an all-time record if it doesn’t get below 80 by midnight — which would probably only happen if there were downburst winds in an unexpected thunderstorm. Starting out so warm substantially increases the chances of reaching 100 degrees today, which has not happened in June at Roanoke since 1959. Widespread 92-104 high temperatures will occur today across most of Virginia aside from the highest ridgetops today. A massive dome of hot, dry air, originating in the Desert Southwest, not the Gulf of Mexico where we typically see hot and more humid air masses come from, is overspreading our region, and being forced downward by high pressure. West to northwest surface winds rotating around the hot high pressure system are blowing down the slopes of the Appalachians, further compressing and heating that air. It’s a scenario that has led to some of our hottest days historically.
Daily record highs for June 29 are 101 at Roanoke (1934) and 92 for Blacksburg (1954). Blacksburg’s record appears very likely to fall, as it’s already in the low 80s there this morning. Roanoke’s record also appears to have a better than even-odds chance of being tied or broken, now. While it has been at least 100 six times since 2000, Roanoke has only been above 100 twice since 1988 — highs of 101 and 102 on August days in 2007.
For those looking for relief — there are indications the hot high will be pulled westward and northward, allowing more of a northwest wind flow and some cold fronts, mid to late next week. But will be several very hot days between now and then.