An isolated severe thunderstorm was able to develop during the afternoon of July 12th as convergence across the higher terrain of Grayson County was able to overcome the stability of a relatively dry and stable atmosphere.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS RNK wrote it up.
An isolated severe thunderstorm was able to develop during the afternoon of July 12th as convergence across the higher terrain of Grayson County was able to overcome the stability of a relatively dry and stable atmosphere.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Blacksburg, VA wrote its last area forecast discussion before the first event at Jul 12, 12:47 PM EST, 2 hours 33 minutes earlier.
Area Forecast Discussion National Weather Service Blacksburg VA 147 PM EDT Wed Jul 12 2017 .SYNOPSIS... A large Bermuda high will remain in control of our weather through the latter portion of the week as it pumps hot and humid air into the region, with an increasing chance for showers and thunderstorms. A cold front will then move slowly through the region Friday and Saturday with a good chance of thunderstorms, followed by improving conditions on Sunday. As another front approaches from the northwest, unsettled weather with a chance for showers and thunderstorms will return to the Appalachians and central mid Atlantic region for the first part of next week. && .NEAR TERM /THROUGH THURSDAY/... As of 245 PM EDT Wednesday... No significant change in the synoptic pattern as a Bermuda high off the coast remains in control of our weather and zonal flow aloft keeps the active track of convective complexes well off to our north. Expect any isolated cells that manage to develop from the southern Blue Ridge into the mountains of NC to dissipate early this evening with dry conditions overnight. Expect any late night fog formation to be primarily along the river valleys west of the Blue Ridge. Expect an increase in chances for showers/thunderstorms tomorrow as a weak influx of short wave energy approaches from the south and increasing moisture generates a bit more instability. Temperatures tonight will remain quite warm with low/mid 70s east of the Blue Ridge and low/mid 60s to the west. The heat stays on for Thursday with low/mid 90s east to mid 80s/around 90 west. Heat index values will once again top 100 east of the Ridge so stay hydrated and take frequent breaks when outdoors. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 245 PM EDT Wednesday... A cold front will gradually approach and then cross the area during this portion of the forecast. Moisture will continue to pool in advance of the front Thursday night through Friday. This and increased dynamics aloft with the approach of the front should allow for generous coverage of showers and storms by the afternoon on Friday, especially across the mountains. The front is expected to crosses the region Friday night into early Saturday morning. Its proximity to the area on Saturday will help maintain isolated to scattered showers and storms across primarily the southern half the area during the day Saturday. The latest Day 3 Convective Outlook from the Storm Prediction Center place a Marginal risk of severe weather over the forecast area Friday and Friday night. The greatest severe weather threat is isolated damaging winds. High temperatures will continue average about five degrees above normal during this portion of the forecast with low temperatures close to ten degrees above normal. Readings will be slightly cooler on Saturday as compared to Friday. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 245 PM EDT Wednesday... During this period of the forecast an upper ridge will remain parked across Rockies and Plains States, keeping a general northwest flow pattern across our region. Within this flow regime, a series of upper level troughs will cross our area, each with the potential for accompanying daily showers and storms. By Wednesday, uncertainty grows in regards to whether or not the upper ridge makes enough progress eastward and squelch convection over our region, or we remain in the troughy regime. Our forecast will lean toward the "not" side. Temperatures during this portion of the forecast will still average above normal, but be a couple of degrees cooler on average than the days leading into the weekend. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 245 PM EDT Wednesday... Bermuda high off the coast will remain in control of our weather through the TAF period, but the pattern of diurnal convection will be trending upward as added warmth in the boundary layer and orographic affects in the mountain start to overcome the convective cap. Coverage through this evening will be sparse and confined to the southern Blue Ridge into the mountains of North Carolina and expect no impact to TAF sites. Convection by tomorrow afternoon convection will increase in coverage but will not attempt to discern particulars toward the end of the period and will simply include VCTS for sites along/west of the Blue Ridge late in the period. Expect cigs/vsbys to generally be VFR with some late night fog/stratus possible mainly at KLWB and KBCB, though the trend over the past few nights has been for minimal coverage outside of the immediate river valleys west of the Blue Ridge. Winds will generally be light through the period. Aviation Extended Discussion... Thursday there is a slightly better probability of thunderstorms in the afternoon and evening. Late night/early morning fog/low clouds are again expected Thursday night. Scattered to numerous MVFR showers and thunderstorms are possible for Friday and Saturday with the passage of a cold front. Sunday will be drier with overall VFR conditions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...DS LONG TERM...DS AVIATION...MBS/DS
Hazardous Weather Outlook National Weather Service Blacksburg VA 428 AM EDT Wed Jul 12 2017 NCZ001>006-018>020-VAZ007-009>020-022>024-032>035-043>047-058-059- WVZ042>044-507-508-131100- Ashe-Alleghany NC-Surry-Stokes-Rockingham-Caswell-Watauga-Wilkes- Yadkin-Tazewell-Smyth-Bland-Giles-Wythe-Pulaski-Montgomery-Grayson- Carroll-Floyd-Craig-Alleghany VA-Bath-Roanoke-Botetourt-Rockbridge- Patrick-Franklin-Bedford-Amherst-Henry-Pittsylvania-Campbell- Appomattox-Buckingham-Halifax-Charlotte-Mercer-Summers-Monroe- Eastern Greenbrier-Western Greenbrier- 428 AM EDT Wed Jul 12 2017 This Hazardous Weather Outlook is for north central North Carolina, northwest North Carolina, central Virginia, south central Virginia, southwest Virginia, west central Virginia and southeast West Virginia. .DAY ONE...Today and tonight. Hazardous weather is not expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Scattered to numerous thunderstorms are expected Friday afternoon and evening. A few of these could become strong to severe, with damaging wind gusts the main threat. For the remainder of the period, the probability of widespread hazardous weather is low at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. RAB
Special Weather Statement National Weather Service Blacksburg VA 236 PM EDT Wed Jul 12 2017 NCZ001>003-018-019-VAZ015>017-032-033-122100- Ashe-Alleghany NC-Surry-Watauga-Wilkes-Grayson-Carroll-Floyd- Patrick-Franklin- Including the cities of West Jefferson, Sparta, Dobson, Boone, Wilkesboro, Independence, Whitetop, Troutdale, Volney, Galax, Floyd, Stuart, and Rocky Mount 236 PM EDT Wed Jul 12 2017 ...SLOW MOVING THUNDERSTORMS THIS AFTERNOON... Slow moving thunderstorms will form along the eastern slopes of the southwest Virginia and northwest North Carolina Blue Ridge through the afternoon. These storms are capable of producing heavy rainfall of an inch or so and gusty winds up to 40 mph as they collapse. The lifetime of these thunderstorms are around 30 minutes. Outflow boundaries from decaying storms may generate more storms into this evening for counties bordering the Blue Ridge. RCS
The Roanoke radar (KFCX), 78 km away, was scanning. The volume nearest the first event began at 20:17 UTC.
1 thunderstorm wind, 1 hail. Local standard time, as filed.
Thunderstorm winds caused a six-inch diameter limb to fall in a homeowner’s backyard.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Virginia in 2017Every state in 2017This day in weather historyWarnings in Virginia, July 2017
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 700744, 700745.