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, 1:24 PM EST, 24 minutes earlier.
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
224 PM 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 satellite and radar imagery continues to show scattered
showers and thunderstorms beginning to develop across the
eastern edge of West Virginia. Storms will continue to propagate
eastward through the remainder of the afternoon through early
this evening. A Severe Thunderstorm Watch has been issued for
areas along and east of the Blue Ridge through 8PM this evening.
Bermuda high pressure remains 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. Guidance continues to depict high CAPE
values between 2000-2500 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, expecting today would be no different, especially
given the current development of storms. 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/...
Cold front will slowly continue to sink southeastward Saturday.
Guidance continues to indicate the slow moving nature of the
front as most of the 12Z guidance indicates some partial
sunshine during the morning hours. While temperatures will be
cooler than what we've seen as of late, low 90s are still
anticipated across our southeast areas with mid to upper 80s
elsewhere and even cooler across the higher terrain as cooler
air begins to advect in from the northwest.
Depending on the amount of sunshine we receive during the
morning hours, with dew points still in the 70s across much of
the area, will add to the overall instability, resulting in
another round of widespread showers and thunderstorms for the
afternoon and evening. However there appears to be a lesser
threat of severe thunderstorms and more so looks favorable for
flood risk. Given the high instability, slow moving nature of
the front, high PWATS and shortwave energy traversing along the
boundary, gives concern for training storms that would cause
instances of flooding. Greatest threat looks to remain across
our central and southern portions of the CWA. As a result, WPC
has this area poised for a slight risk for excessive rainfall.
The front should then be more displaced just south of the region
as strong high pressure builds over the Great Lakes. However,
the front will be wedged as it runs into the strong Bermuda High
off the Carolinas. Thus, could see additional showers and
storms across our southernmost areas throughout the day Sunday.
However confidence remains low on the exact impacts at this
time. Overall temperatures will be much cooler Sunday with highs
in the low 80s for most, coupled with lower humidity.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Come Monday, an upper level ridge will be building across the
southeast US while a trough resides near the Great Lakes. A front
will remain stalled between these two upper level features near the
Virginia/Carolina border and slowly lift northward towards the local
area. This front will be the focus for showers and thunderstorms as
tropical moisture is advected northward from the Gulf of Mexico and
interacts with the frontal boundary resulting in likely rain chances
through midweek.
Tropical Depression Fred (see hurricanes.gov for the latest official
forecast) could also impact the region next week. While the track of
Fred remains uncertain, should Fred track towards the local area,
the additional tropical moisture combined with the stalled frontal
boundary could be hydrologically problematic. However, since most
locations west of the Blue Ridge are in the abnormally dry or
moderate drought category (see drought.gov for details), this rain
could be beneficial if it falls over the course of several days and
not in a short period of time. There is a fair amount of uncertainty
between global deterministic guidance with the ECMWF bringing more
moisture from Fred north to the local area while the GFS has Fred
dissipating over the interior southeast US.
Temperatures to start next week will be notably cooler than this
past week due to more cloud cover and an easterly flow off the
Atlantic. Temperatures will moderate towards midweek as the flow
becomes more southerly, though rain and cloud cover will still keep
temperatures in the mid 80s for most.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
VFR conditions continue 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.
Showers and thunderstorms could result in periods of daily sub VFR
conditions during the afternoon and evening hours through midweek.
are becoming more likely Monday and Tuesday due to the increased
risk for showers and thunderstorms. There could also be brief
reductions in vsbys due to low clouds/fog each morning.
Easterly/southeasterly winds will become more southerly by
midweek.
&&
.MARINE...
Winds will generally remain below SCA levels through Saturday.
Saturday night. However the passage of a cold front may allow
northerly gusts of 20 knots across portions of the waters late
Saturday night into early Sunday morning. However confidence on
this remains low at this time. Thus will continue to monitor
trends. Gusty showers and potentially severe thunderstorms are
expected to develop across the waters late this afternoon
through early this evening, prompting the issuance of SMWs.
Similar conditions may arise Saturday afternoon/evening for
southern portions of the waters.
Winds are expected to remain below SCA criteria Monday into Tuesday
with a stalled front nearby and high pressure to the north.
Strong/gusty winds are possible in any showers and thunderstorms
over the waters mainly during the afternoon and evening hours.
&&
.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
NEAR TERM...SOUZA
SHORT TERM...SOUZA
LONG TERM...CPB
AVIATION...SOUZA/CPB
MARINE...SOUZA/CPBHazardous 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.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
246 PM EDT FRI AUG 13 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0207 PM TSTM WND DMG 1 NNE MOSCOW 38.33N 79.08W
08/13/2021 AUGUSTA VA EMERGENCY MNGR
NUMEROUS TREES AND POWERLINES DOWN IN THE MOUNT SOLON
AREA, ESPECIALLY ALONG MOSCOW LOOP TOWARDS HWY 42 FROM
MOSSY CREEK ROAD
&&
EVENT NUMBER LWX2105269
ADMThe Sterling radar (KLWX), 85 km away, was scanning. The volume nearest the first event began at 18:48 UTC.
39 thunderstorm wind, 2 lightning. Local standard time, as filed.
A wind gust of 39 knots (45 MPH) was measured by the ASOS at Hagerstown Regional Airport (KHGR). A tree was reported down on southbound I-81 at Showalter Road next to the airport.
A tree was reported down on southbound US-15 Catoctin Mountain Highway at Auburn Road.
There were several reports of wires blown down near Middletown.
Trees blew down on northbound US-40 Baltimore National Pike near Gambrills Park Road.
Wires blew down in the 7600 block of McKaig Road. A tree blew down onto wires on McKaig Road past Allview Drive.
Trees blew down on southbound MD-75 Walnut Street near Jones Road.
A tree was reported down in the 1500 block of Bowersox Road.
Trees blew down near the intersection of MD-190 River Road and Travilah Road.
A wind gust of 50 knots (58 MPH) was measured by a mesonet in Germantown.
Numerous trees blew down near Germantown and Boyds. Numerous trees blew down in the 17000 block of Germantown Road. Several large pine trees snapped and dozens of large tree limbs blew down near the Maryland Soccerplex; soccer goals and Porta Potties blew over. Trees blew down on MD-117 Clopper Road near Mateny Road. A large tree blew down on Central Park Circle at the South Germantown Recreational Park.
Numerous trees and wires blew down in the Damascus and Laytsonville area. Multiple trees blew down near the intersection of MD-94 Annapolis Rock Road and MD-108 Damascus Road. Multiple trees blew down near the intersection of MD-108 Laytonsville Road and MD-650 Damascus Road. A tree blew down near the intersection of MD-124 Woodfield Road and Sweepstakes Road. A tree blew down near the intersection of Hawkins Creamery Road and Woodfield School Road. Wires blew down in the 24800 block of MD-124 Woodfield Road. Wires blew down in the 25900 block of MD-27 Ridge Road. Trees and wires blew down on MD-124 near Greenel Road. Power lines blew down in the unit block of Clearwater Court. Power lines blew down in the 9500 block of Pleasant Plains Road.
Trees blew down on MD-94 Woodbine Road near Annapolis Rock Road.
Numerous trees blew down in the Woodbine area.
Numerous trees blew down in the Dayton and Glenwood area. Trees blew down near the intersection of McNeal Road and Union Chapel Road. Trees blew down near the intersection of Gared Road and Sharp Road.
Numerous trees blew down in the West Friendship area.
Wires were reported down near the intersection of MD-586 Veirs Mill Road and Newport Mill Road causing a fire.
Trees blew down near the intersection of US-40 Baltimore National Pike and MD-144 Frederick Road. A large tree blew down near the intersection of Ten Oaks Road and Green Bridge Road. Trees blew down on MD-99 Old Frederick Road near Taylor Farm Road.
Several trees blew down in the Columbia area. A tree blew down on Launcelot Lane. Two trees blew down near the intersection of Broken Lane Parkway and Patuxent Woods Drive.
Trees blew down on northbound I-83 at mile marker 35.
A few hundred trees blew down throughout the City of Baltimore. A large tree and several branches were blown down near the intersection of Biltmore Avenue and Pinkey Road.
A lightning strike caused a fire that burned a shed and fence in the 1900 block of Reedie Drive.
A tree blew down on Hess Road near MD-146 Jarresttsville Pike.
Trees blew down on southbound MD-136 Harkins Road prior to Linkous Road. Trees blew down on MD-24 Rocks Road near Saint Mary's Road.
Several trees blew down in and around Fallston. Trees blew down near the intersection of MD-152 Fallston Road and Carrs Mill Road. A tree blew down on MD-152 Fallston Road near Rochelle Drive. A tree blew down near the intersection of Durham Road and Bellechase Road. A tree blew down in the 2800 block of Pleasantville Road.
Numerous trees blew down in and around Street and Pylesville. A tree blew down near the intersection of Coen Road and Rocks Road. A tree blew down onto wires causing a fire on southbound MD-543 Ady Road near Brinegar Road. A tree blew down near the intersection of Whiteford Road and Macton Road. A tree blew down blocking the roadway in the 1100 block of Harkins Road. A tree blew down in the 4900 block of Rocks Road. A tree blew down near the intersection of Saint Paul's Church Road and Telegraph Road.
Several trees and power lines blew down in and around Bel Air. Power lines blew down in the 300 block of Baltimore Pike. A tree blew down near the intersection of Jade Drive and Emerald Drive.
Trees blew down on southbound MD-197 near Race Track Road.
A lightning strike blew apart a fire place in the 1400 block of Baldwin Mill Road.
Trees blew down near the intersection of MD-193 Watkins Park Drive and Keverton Drive. Trees blew down on MD-193 Watkins Park Drive near Oak Grove Road.
A tree blew down at mile marker 1 on MD-23 East-West Highway.
A tree blew down in the 1400 block of Hollingsworth Road. A branch blew down onto wires causing a fire in the 3000 block of Clayton Road.
Wires blew down near the intersection of MD-424 Davidsonville Road and MD-214 Central Avenue.
Trees blew down on MD-4 Southern Maryland Boulevard near MD-408 Mount Zion Marlboro Road.
A tree blew down on southbound MD-222 Susquehanna River Road near US-1 Conowingo Road.
Trees blew down on MD-468 Muddy Creek Road near MD-255 Galesville Road.
Trees blew down near the intersection of MD-725 Main Street and MD-202 Largo Road.
Numerous trees and wires were blown down in the Morgantown and Newburg areas. Trees blew down on US-301 Crain Highway near Edge Hill Road.
Numerous trees and power lines were blown down in the Cobb Island area.
Several trees blew down along Yowaiski Mill Road in Mechanicsville. Trees blew down on MD-238 Maddox Road near Vixen Run Lane. Several trees blew down along MD-5 Point Lookout Road in Leonardtown.
Several trees blew down along Yowaiski Mill Road in Mechanicsville. Trees blew down on MD-238 Maddox Road near Vixen Run Lane. Several trees blew down along MD-5 Point Lookout Road in Leonardtown.
Several trees and wires blew down in the Prince Frederick area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2021Every state in 2021This day in weather historyWarnings in Maryland, 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: 966706, 966707, 966708, 966709, 966710, 966711, 966712, 966713, 966714, 966715, 966716, 966717, 966718, 966719, 966720, 966721, 966722, 966723, 966724, 966725, 966726, 966727, 966728, 966729, 966730, 966731, 966732, 966733, 966734, 966735, 966736, 966737, 966738, 966739, 966740, 966741, 966742, 966743, 966744, 966745, and more.