A cold front intersected an extremely unstable airmass. The result was numerous strong to severe thunderstorms containing damaging wind gusts and some hail.
Every event with a place to put it. Tap one for its entry below.
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 LWX wrote it up.
A cold front intersected an extremely unstable airmass. The result was numerous strong to severe thunderstorms containing damaging wind gusts and some hail.
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 Baltimore/Washington wrote its last area forecast discussion before the first event at Aug 13, 9:03 AM EST, 4 hours 11 minutes earlier.
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1003 AM EDT Fri Aug 13 2021
.SYNOPSIS...
High pressure will remain offshore today as a cold front slowly
approaches from the northwest. The front will push through our
area on Saturday before eventually stalling across our southeast
Sunday through early next week. Eventually the front will
return back northward as a warm front toward the middle of next
week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Latest analysis shows Bermuda high pressure banked off the
Carolina coastline as an H5 trough continues to slowly dip
southward across the Great Lakes region as it gradually shifts
eastward through the weekend. As a result, an associated cold
front will approach from the northwest this afternoon. Dangerous
heat and humidity continues today with highs in the mid to upper
90s for most, along with dew points in the mid to upper 70s. As
a result, heat indices continue to range between 100-107
degrees. The combination of the high heat/humidity will lead to
quite the unstable atmosphere. Latest guidance continues to
depict high CAPE values between 2500-3000 J/Kg. DCAPE values
also range between 800-1200 J/Kg across the region with steep
low level lapse rates and decent mid level lapse rates around
7.5C/Km. Given the stronger forcing and the development of a
bay breeze off the Chesapeake, do expect there to be a
convergence boundary across central VA and north-central MD,
further accelerating storm development. Shear does remain rather
weak. However given these atmospheric parameters are similar to
that observed earlier in the week, thinking that today would be
no different. West to east storm development looks to occur
mainly after 2PM before reaching the metro areas by late
afternoon/early evening. Main hazards associated with any severe
storms will be damaging wind gusts.
Expect storms to die out this evening after heating ends and
the shortwave passes east, with late night turning out dry and
muggy again.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
...PREVIOUS DISCUSSION...
Cold front will slowly but surely move southeastward across the
region on Saturday. Guidance is most insistent on widespread
showers and thunderstorms, though some question remains on just
how much severe weather may occur given CAPE may be limited by
the clouds and precip arriving fairly early in the day. That
said, shear from the passing shortwave may be enough despite
potentially lower CAPE available, and with high PW's and
potential training, a flood risk is also present. The clouds and
rain, not to mention the passing front, should result in a
notably cooler day, with highs falling back closer to seasonal
norms.
Front should pass just south of the region by Sunday, with high
pressure trying to build in from the north. However, guidance is
consistent in the front stalling just to the south, and a moist
easterly flow may set up just north of it. Bottom line is that
while Sunday will be cooler and not as wet, it may still not be
a great day considering clouds and a few showers may linger,
especially in central VA. Highs should stay below normal for a
change.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
A frontal boundary remains stall to our south early next week
as high pressure situates itself to our north. This boundary
looks to diffuse by midweek as the remnants of Tropical
Depression Fred potentially makes its way into the region.
Resultant weather for much of the long term portion of the
forecast will be above normal rain chances with the
aforementioned boundary to our south, flow favoring an onshore
trajectory, and moisture from Fred nearing the region by
midweek. Additionally, we look to be wedged between an upper
level ridge to our southeast and a trough to our northwest,
helping funnel moisture northward across the region.
Ample cloud cover and increased rain chances will keep
temperatures in check compared to this week, with highs in the
low to middle 80s, and lows falling back into the 60s. Winds
turn more southerly by around midweek, allowing temperatures to
nudge upwards a bit, but with elevated rain chances continuing,
they'll likely remain just below climatology.
&&
.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
VFR conditions overall through Sunday night. Main concern will
be potential for thunderstorms this afternoon/evening and again
Saturday afternoon/evening. Some shower risk persists Sunday but
looks lower compared to the preceding days as the cold front
should press further south by then. Patchy late night/early
morning fog may also occur in locations which receive storms the
prior evening, particularly at MRB/CHO late tonight.
Periods of sub VFR conditions look increasingly likely early
next week with elevated shower and thunderstorm chances, focused
during the afternoon and evening hours. Winds will favor a
southeasterly trajectory at the terminals early next week as
high pressure resides to the north.
&&
.MARINE...
Winds will generally remain below SCA levels through Saturday.
Saturday night, the passage of a cold front may allow northerly
gusts of 20 knots, necessitating an SCA which may linger into
Sunday. Winds should diminish by Sunday night.
High pressure will reside to our north early next week as winds
trend out of the southeast. The gradient appears weak enough to
maintain sub SCA gusts over the marine district. Elevated
chances for afternoon and evening showers and thunderstorms may
present a gusty wind threat.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory until 7 PM EDT this evening for DCZ001.
MD...Heat Advisory until 7 PM EDT this evening for MDZ003>006-008-
011-013-014-016>018-501>508.
VA...Heat Advisory until 7 PM EDT this evening for VAZ026>031-
036>040-050>057-501-502-505-506.
WV...Heat Advisory until 7 PM EDT this evening for WVZ050>053-055-
502>504.
MARINE...None.
&&
SYNOPSIS...SOUZA/RCM
NEAR TERM...SOUZA/RCM
SHORT TERM...RCM
LONG TERM...BKF
AVIATION...BKF/RCM
MARINE...BKF/RCMHazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 122 PM EDT Fri Aug 13 2021 ANZ530>543-DCZ001-MDZ008-011-013-014-016>018-504-506-508- VAZ052>057-141730- Chesapeake Bay north of Pooles Island MD- Chesapeake Bay from Pooles Island to Sandy Point MD- Chesapeake Bay from Sandy Point to North Beach MD- Chesapeake Bay from North Beach to Drum Point MD- Chesapeake Bay from Drum Point MD to Smith Point VA- Tidal Potomac from Key Bridge to Indian Head MD- Tidal Potomac from Indian Head to Cobb Island MD- Tidal Potomac from Cobb Island MD to Smith Point VA- Patapsco River including Baltimore Harbor- Chester River to Queenstown MD-Eastern Bay- Choptank River to Cambridge MD and the Little Choptank River- Patuxent River to Broomes Island MD- Tangier Sound and the inland waters surrounding Bloodsworth Island-District of Columbia-Cecil-Southern Baltimore- Prince Georges-Anne Arundel-Charles-St. Marys-Calvert- Central and Southeast Montgomery-Central and Southeast Howard- Southeast Harford-Prince William/Manassas/Manassas Park-Fairfax- Arlington/Falls Church/Alexandria-Stafford-Spotsylvania- King George- 122 PM EDT Fri Aug 13 2021 This Hazardous Weather Outlook is for the Maryland portion of the Chesapeake Bay, Tidal Potomac River, and I-95 corridor through central Maryland, northern Virginia, and District of Columbia. .DAY ONE...This Afternoon and Tonight A Severe Thunderstorm Watch is in effect until 8 PM for the outlook area. Scattered severe thunderstorms with damaging wind gusts and isolated large hail are possible. Isolated instances of flash flooding are possible through early this evening. A Heat Advisory is in effect for the entire outlook area from 11 AM to 7 PM today. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Isolated severe storms along with isolated instances of flash flooding are possible during the afternoon and evening hours Saturday. Heavy rain and flooding possible from tropical moisture Monday into Tuesday and potentially continuing into Wednesday due to the remnants of Fred. .SPOTTER INFORMATION STATEMENT... Spotter activation may be necessary for Friday afternoon to evening. MDZ003>006-503-505-507-VAZ025>031-036>040-050-051-501-502-505>508- WVZ050>053-055-141730- Washington-Frederick MD-Carroll-Northern Baltimore- Northwest Montgomery-Northwest Howard-Northwest Harford-Augusta- Rockingham-Shenandoah-Frederick VA-Page-Warren-Clarke-Nelson- Albemarle-Greene-Madison-Rappahannock-Orange-Culpeper- Northern Fauquier-Southern Fauquier-Western Loudoun- Eastern Loudoun-Northern Virginia Blue Ridge- Central Virginia Blue Ridge-Hampshire-Morgan-Berkeley-Jefferson- Hardy- 122 PM EDT Fri Aug 13 2021 This Hazardous Weather Outlook is for portions of eastern West Virginia, northern and central Virginia, and central and western Maryland. .DAY ONE...This Afternoon and Tonight A Severe Thunderstorm Watch is in effect until 8 PM for the outlook area. Scattered severe thunderstorms with damaging wind gusts and isolated large hail are possible. Isolated instances of flash flooding are possible through early this evening. A Heat Advisory is in effect for most of the outlook area from 11 AM to 7 PM today. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Isolated severe storms along with isolated instances of flash flooding are possible during the afternoon and evening hours Saturday. Heavy rain and flooding possible from tropical moisture Monday into Tuesday and potentially continuing into Wednesday due to the remnants of Fred. .SPOTTER INFORMATION STATEMENT... Spotter activation may be necessary for Friday afternoon to evening. MDZ001-501-502-VAZ503-504-WVZ501>506-141730- Garrett-Extreme Western Allegany-Central and Eastern Allegany- Western Highland-Eastern Highland-Western Grant-Eastern Grant- Western Mineral-Eastern Mineral-Western Pendleton- Eastern Pendleton- 122 PM EDT Fri Aug 13 2021 This Hazardous Weather Outlook is for the Allegheny Front counties in western Maryland, eastern West Virginia, and Highland County Virginia. .DAY ONE...This Afternoon and Tonight Isolated severe storms along with isolated instances of flash flooding are possible during the afternoon and evening hours today. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Isolated severe storms along with isolated instances of flash flooding are possible during the afternoon and evening hours Saturday. Heavy rain and flooding possible from tropical moisture Monday into Tuesday and potentially continuing into Wednesday due to the remnants of Fred. .SPOTTER INFORMATION STATEMENT... Spotter activation may be necessary for Friday afternoon to evening.
The Sterling radar (KLWX), 156 km away, was scanning. The volume nearest the first event began at 18:11 UTC.
47 thunderstorm wind, 1 lightning, 1 hail. Local standard time, as filed.
Numerous trees and power lines were blown down in the Mount Solon area, especially along VA-731 Moscow Loop/Natural Chimney Road between VA-42 Scenic Highway and VA-747 Mossy Creek Road.
A wind gust of 55 knots (63 MPH) was measured by a mesonet near High View Manor. Trees blew down nearby in the 4100 block of VA-622 Cedar Creek Grade.
A wind gust of 53 knots (61 MPH) was measured by a mesonet near the intersection of VA-752 Muddy Creek Road and VA-726 Mount Clinton Pike where trees blew down. A large tree also blew down at a residence nearby in the 2100 block of VA-760 Custers Road. Numerous trees blew down on US-33 Rawley Pike between Harrisonburg and Hinton.
Large tree limbs blew down on VA-600 North Hayfield Road.
Wires blew down in the 9200 block of Valley View Road.
Numerous trees and wires blew down near and south of Stephens City. A tree blew down in the 500 block of Peace and Plenty Lane. Numerous large trees blew down on VA-735 Salem Church Road. A tree blew down near the intersection of VA-277 Fairfax Pike and Warrior Drive.
Wires blew down near the intersection of VA-609 Naked Creek Road and VA-758 Fox Mountain Road.
Wires blew down in the 15200 block of VA-657 Albano Road.
A tree blew down in the 1300 block of VA-616 Good Hope Church Road.
A tree blew down near the intersection of US-250 Rockfish Gap Turnpike and VA-151 Critzer Shop Road.
A large tree blew down near the intersection of US-250 Ivy Road/Rockfish Gap Turnpike and VA-240 Three Nothced Road.
Power lines blew down on Blue Ridge Avenue near East Prospect Street.
Lightning struck a transformer causing a fire near the intersection of US-340 Lord Fairfax Highway and Gun Barrel Road.
A large tree blew down near the intersection of VA-664 Ridge Road and Marsh Run Lane.
A tree blew down onto power lines near the intersection of US-29 Thomas Nelson Highway and VA-671 Stage Road. About half a dozen other trees blew down in the area.
Power lines blew down in the 100 block of VA-661 Fairground Road.
A tree blew down near the intersection of VA-604 Celt Road and William Monroe Trail. A tree blew down on VA-810 Dyke Road. A tree blew down in the 400 block of VA-743 Advance Mills Road.
A large tree blew down blocking the 800 block of VA-677 Old Ballard Road. A tree blew onto power lines in the 4200 block of Burton Road.
A tree blew down near the intersection of VA-231 North Blue Ridge Turnpike and Holden Lane. A tree blew down near the intersection of VA-641 Weaver Hollow Road and VA-609 West Hoover Road.
A tree was reported down in the 2100 block of VA-688 Leeds Manor Road.
A tree blew down near the intersection of VA-655 Blue Run Road and VA-20 Constitution Highway.
A tree blew down in the 1400 block of VA-616 Carpenters Mill Road. A tree blew down near the intersection of VA-607 Matthew Mill Road and Sterling Lamm Drive.
A tree blew down on VA-842 Covesville Lane near US-29 Monacan Trail Road. A tree blew down in the 4800 block of VA-692 Plank Road.
Large tree limbs blew down on VA-621 South Blue Ridge Turnpike.
A tree blew down near the intersection of VA-609 West Hoover Road and VA-604 Arrington Mountain Road/Towles Road.
A tree blew down near the intersection of VA-646 Lovers Lane and Briar Patch Drive. A tree blew down in the 300 block of Bock Street. A tree blew down near the intersection of VA-643 Cox Mill Road and VA-648 Browntown Road.
Wind gusts of up to 64 knots (74 MPH) were measured by the AWOS at Warrenton Airport. Numerous large trees several feet in diameter were uprooted with other trees and large branches toppled and snapped in the area, including near the intersection of VA-610 Midland Road and Airport Road.
Large trees, branches, and wires were down near the Northern Virginia Community College - Loudoun Campus. Poles and traffic light stands were brought down near the intersection of VA-7 Harry Byrd Highway and Campus Drive.
Multiple trees blew down in the Great Falls area. Trees blew down on VA-603 Beach Mill Road near Patowmack Drive. A large tree blew down in the 9800 block of Arnon Chapel Road.
Trees blew down near the intersection of VA-600 Beverleys Mill Road and US-29/US-15 Lee Highway. A tree blew down in the 6600 block of VA-675 Kelly Road.
Trees blew down near the intersection of VA-28 Catlett Road and Smith Midland Lane. Trees blew down in the 5100 block of Germantown Road.
A tree blew down near the intersection of Kennedy Road and Vint Hill Parkway.
A tree blew down on Beverley Mill Drive near I-66.
Trees and wires blew down on MD-193 Georgetown Pike between VA-674 Springvale Road and VA-681 Walker Road.
Numerous trees blew down near the intersection of VA-616 Casanova Road and VA-643 Meetze Road.
Numerous trees blew down in the 8900 block of VA-667 Old Dumfries Road. Numerous trees blew down on VA-616 Casanova Road near Poplar Springs Manor.
A tree blew down on VA-609 Courthouse Road.
There were about a dozen calls for trees and wires down.
Numerous trees, branches and wires blew down in the Oakton, Reston, Vienna, and Wolf Trap areas. Trees blew down on VA-677 Hunter Station Road near Roundhouse Road. A large tree blew down near the intersection of Wendover Drive and Round Springs Drive. Trees blew down near the intersection of Wendover Drive and Bird Drive. A large tree blew down in the 2300 block of Trott Avenue. A large tree blew down near the intersection of Clarks Crossing Road and Elgin Drive. Trees blew down near the intersection of Clover Glen Drive and Barnwood Terrace.
Golf ball size hail was reported in Oakton.
Trees blew down near the intersection of Worcester Drive and Laurel Street.
Several trees blew down in the Widewater area.
Several trees blew down in the Merrifield, Idylwood, Annandale, Springfield and Lincolnia areas. Trees blew down on Brookside Drive near VA-236 Little River Turnpike. Trees blew down on Earlehurst Street near Leesville Boulevard. A large tree blew down near the intersection of Oak Street and Morgan Lane. Trees blew down on Heming Avenue. Trees blew down near the intersection of Beau Lane and Hideaway Road. Trees blew down near the intersection of Sandburg Street and Sandburg Court.
Several trees blew down in the Brooke area.
Several trees blew down in the White Oak area.
Trees blew down on VA-621 Marlborough Point Road near Potomac Overlook Lane.
Trees blew down near the intersection of VA-694 Lambs Creek Church Road and VA-608 Igo Road.
Trees blew down near the intersection of VA-607 Port Conway Road and VA-660 Canning Way.
Trees blew down near the intersection of VA-218 Caledon Road and Bluff Way. The 911 Call Center reported about two dozen calls for trees and wires down throughout the area. Several cars struck fallen trees in the roadway, but no injuries were reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Virginia in 2021Every state in 2021This day in weather historyWarnings in Virginia, August 2021
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: 966657, 966659, 966658, 966660, 966661, 966662, 966663, 966664, 966665, 966666, 966670, 966667, 966668, 966669, 966671, 966672, 966673, 966674, 966675, 966676, 966677, 966678, 966679, 966680, 966681, 966682, 966683, 966684, 966685, 966686, 966687, 966688, 966689, 966690, 966691, 966692, 966693, 966694, 966695, 966696, and more.