A disturbance (the remnant of convection from over the Ohio River Valley the day before) triggered a line of strong to severe thunderstorms that affected mainly northern Maryland and far northern Virginia during the early evening hours of Wednesday, September 2nd, 2020.
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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 LWX wrote it up.
A disturbance (the remnant of convection from over the Ohio River Valley the day before) triggered a line of strong to severe thunderstorms that affected mainly northern Maryland and far northern Virginia during the early evening hours of Wednesday, September 2nd, 2020.
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 Sep 2, 1:31 PM EST, 4 hours 18 minutes earlier.
Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 231 PM EDT Wed Sep 2 2020 .SYNOPSIS... Multiple fronts will affect our region through Friday bringing multiple chances for severe weather. High pressure returns this weekend along with mostly dry weather. && .NEAR TERM /THROUGH TONIGHT/... The front that has been stalled/wedged over our region has moved northward as a warm front this afternoon. Cloud cover has started to break up with the low level cloud deck slowly becoming scattered in nature. We still have an area of high clouds but majority of area is seeing decent sunshine. The increased heating coupled with dewpoint temps in the low to mid 70s will lead to CAPE values from 1500 to 2000 this afternoon and into this evening. A cold front will slowly approach from our west late this afternoon and into this evening. The main boundary will remain off to our west and northwest through the rest of the day. The best upper level forcing will be focused to our north with 250mb jet located over PA and the main shortwave energy near the Mason Dixon Line. A MCV currently over portions of WV and southern VA will move into our region over the next few hours. This system coupled with good low level shear and decent CAPE will lead to isolated to scattered strong to severe thunderstorms this afternoon and into this evening. The decent shear with fair mid level lapse rates will lead to the risk for isolated tornadoes. SPC has upgraded our region to a Slight risk for severe weather with a 5% chance for tornadoes. The risk for showers and thunderstorms should taper off after 4Z with dry conditions expected after 2am. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Dry weather is expected to continue through early Thursday with temps in the 70s. Another higher risk day is expected Thursday afternoon and into early evening. The front to our north will drop southward through the day Thursday. This boundary coupled with warm and moist air advected into our region due to a southerly flow along with strong shortwave will lead to an enhanced risk for severe weather. CAPE values will increase above 2000 as temperatures and moisture increase during the day Thursday. Shear will be better than today which will lead to an increased risk for a tornadoes Thursday. SPC has upgraded our region to an enhanced risk for severe weather with a 10 percent chance for tornadoes. Thursday could be a very dangerous environment with more widespread threat for severe weather and tornadoes. We will to need monitor the changing weather situation to determine the timing, coverage and risk for Severe WX tomorrow. Another front will drop through our region late Thursday and into Friday morning. The thunderstorm threat should be limited Friday morning due to the timing of the frontal passage which should limit CAPE values due to lack of diurnal heating. Dry conditions are expected Friday afternoon and into this weekend as high pressure builds over our region. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... The weekend is continuing to provide a calm, comfortable few days for the area with strong high pressure overhead. Zonal flow will dominate the area Saturday and Sunday with a strong upper level low draping over the Great Lakes and up above Montreal. Monday during the day should remain dry before any shortwave energy makes its way into the region late Monday into Tuesday. ECMWF keeps things away Monday night into Tuesday with an inverted trough off the coast of VA/DE. Other guidance (GFS,CMC) brings in some moisture for the time period. Marginal shear and buoyancy parameters will keep convection to a minimum for the extended period. PWAT values look to be lower into the early part of next week with conditions remaining fairly dry and less humid. Temperatures for the extended period will bring seasonable-to-below seasonable temperatures as we enter early next week. Highs will start out near 80F Saturday and decrease into the later part of the weekend after a weak frontal boundary passes Monday, leading to temperatures struggling to reach the 80s by early next week. Lows will be in the upper 50s to low 60s for the time period. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... Cloud cover continues to scattered out this afternoon with mainly VFR conditions. Period MVFR conditions will be possible but restrictions are expected to remain limited. The main threat for the terminals today and through Thursday will be strong to severe thunderstorms capable of damaging winds and isolated tornadoes. The main threat window today will be 19Z through 2Z. Tomorrow the severe threat earlier with the threat window from 16Z to 00Z. MVFR ceilings and visibilities will be possible Thursday morning and early Friday morning. Dry conditions expected to return Friday afternoon with VFR conditions. VFR conditions expected Saturday and Sunday with the presence of high pressure. && .MARINE... Strong to severe thunderstorms will be possible over our marine areas today and Thursday which may require special marine warnings. No Small Craft Advisories expected at this time for Friday. SCA criteria is not expected to be reached Saturday and Sunday. No marine hazards are expected for the weekend. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && SYNOPSIS...JMG NEAR TERM...JMG SHORT TERM...KJP LONG TERM...ADM AVIATION...JMG/ADM MARINE...JMG/ADM
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 1250 PM EDT Wed Sep 2 2020 ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-031700- 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-Southern Baltimore-Prince Georges- Anne Arundel-Charles-St. Marys-Calvert-Southeast Harford- Prince William/Manassas/Manassas Park-Fairfax- Arlington/Falls Church/Alexandria-Stafford-Spotsylvania- King George- 1250 PM EDT Wed Sep 2 2020 This Hazardous Weather Outlook is for the Maryland portion of the Chesapeake Bay, Tidal Potomac River, and adjacent counties in central Maryland and northern Virginia as well as the District of Columbia. .DAY ONE...This Afternoon and Tonight Isolated severe thunderstorms capable of producing damaging winds are possible late this afternoon and evening. An isolated tornado is possible. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Isolated to scattered severe thunderstorms with damaging wind gusts and isolated tornadoes are possible Thursday afternoon and evening. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed Today and Thursday afternoon. MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053- 055-501>506-031700- Washington-Frederick MD-Carroll-Northern Baltimore- Extreme Western Allegany-Central and Eastern Allegany- Northwest Montgomery-Central and Southeast Montgomery- Northwest Howard-Central and Southeast Howard-Northwest Harford- Augusta-Rockingham-Shenandoah-Frederick VA-Page-Warren-Clarke- Nelson-Albemarle-Greene-Madison-Rappahannock-Orange-Culpeper- Northern Fauquier-Southern Fauquier-Western Highland- Eastern Highland-Western Loudoun-Eastern Loudoun- Northern Virginia Blue Ridge-Central Virginia Blue Ridge- Hampshire-Morgan-Berkeley-Jefferson-Hardy-Western Grant- Eastern Grant-Western Mineral-Eastern Mineral-Western Pendleton- Eastern Pendleton- 1250 PM EDT Wed Sep 2 2020 This Hazardous Weather Outlook is for eastern West Virginia, northern and central Virginia, and central and western Maryland with the exception of Garrett County. .DAY ONE...This Afternoon and Tonight Isolated severe thunderstorms capable of producing damaging winds are possible late this afternoon and evening along and east of the Blue Ridge Mountains. An isolated tornado is possible. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Isolated to scattered severe thunderstorms with damaging wind gusts and isolated tornadoes are possible Thursday afternoon and evening. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed Today and Thursday afternoon.
The Sterling radar (KLWX), 39 km away, was scanning. The volume nearest the first event began at 22:48 UTC.
2 thunderstorm wind. Local standard time, as filed.
A tree was blown down in the 12300 block of VA-671 Harpers Ferry Road.
A tree was blown down near the intersection of VA-9 Charles Town Pike and VA-704 Hamilton Station Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Virginia in 2020Every state in 2020This day in weather historyWarnings in Virginia, September 2020
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: 908935, 908936.