An unstable atmosphere led to a couple thunderstorms becoming severe.
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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.
An unstable atmosphere led to a couple thunderstorms becoming severe.
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 1, 9:04 AM EST, 3 hours 56 minutes earlier.
Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1004 AM EDT Tue Aug 1 2017 .SYNOPSIS... High pressure will hold across the area today and then will move offshore Wednesday and Thursday. A cold front is expected to cross the area late Friday or early Saturday. High pressure will return on Sunday. && .NEAR TERM /THROUGH TONIGHT/... Only a few strands of mid and high level clouds under high pressure this morning. The main focus of the forecast today and tonight will be shortwave energy carving out a bit of a trough in 500 mb flow, which is currently entering the lower Ohio Valley. Initially, any convective development should be tied to the terrain. Coverage may be a bit better today owing to less mid level stability. Also wouldn't totally rule out an isolated shower forming on a bay breeze front given less capping than yesterday. Coverage over the highlands and into the Shenandoah Valley may increase during the late afternoon/early evening as the trough approaches. Deep layer shear is weak, so would still only expect disorganized pulse storms. Due to the timing of the shortwave trough, believe there may be a few showers/a thunderstorm that linger well into the evening. Models continue to dwindle coverage in the diurnal minimum east of the Blue Ridge, but wouldn't totally rule out a stray shower or two persisting overnight. At the very least, have broken cloud cover, which will yield mostly cloudy wording, and could somewhat mitigate the valley fog that occurred this morning. Lows will be in the mid to upper 60s with lower 70s in the urban areas. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Shortwave energy will still be migrating across the area on Wednesday, so there will be a continued risk for widely scattered showers and thunderstorms. Once again, have focused PoPs north/west of Baltimore and Washington where forcing will be greater, but there could be a shower or storm just about anywhere. Will try to keep mention of thunder in the mid-late afternoon hours, but GFS suggesting that there will be decent, uncapped instability prior to noon. There will still be some vorticity in the mean flow Thursday, but it should be less...and confined more to the highlands... as the trough axis retrogrades in response to another vigorous/amplified shortwave. Still have chance PoPs in the mountains, and slight chance Blue Ridge/foothills. Temperatures will be comparable, and seasonable, through the period. && .LONG TERM /FRIDAY THROUGH MONDAY/... A cold front will approach the Mid-Atlantic region Friday. Showers and thunderstorms are possible Friday afternoon into the evening as the front approaches the Appalachians. The cold front is expected to cross the Mid-Atlantic region late Friday into Saturday. This will likely suppress convection however details are uncertain at this time. The front will likely exit to the east by Saturday afternoon. NW winds and dry conditions will move into the region Saturday evening reducing the humidity. High pressure will move overhead Sunday. Slightly below normal temperatures are expected this weekend. High pressure will move off the coast Sunday night and return flow begins Monday. Unsettled weather conditions may kick off the work week. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... VFR conditions anticipated for the valid TAF period at this time. Expect widely scattered showers or a thunderstorm to develop with peak heating today. Coverage will be very sparse, so it is highly unlikely that any terminal will be affected. That very low risk will carry into the evening. MRB/CHO will best candidates as they will be closest to the better forcing. Further, those same sites stand the higher chance at fog development late tonight into Wednesday morning. The pattern will be similar Wednesday and Thursday. Early morning patchy fog will give way to widely scattered showers/thunderstorms. Skill in details low at this time. There is a low chance of flight restrictions Fri-Sat. && .MARINE... Light/variable winds will become onshore late today, and turn south tonight. Flow will generally stay at or below 10 kt through Wed morning, although there may be a hint of southerly channeling late tonight. South flow will then prevail through midweek. Winds may approach Small Craft Advisory thresholds each evening due to channeling. South winds expected on the waters Fri. A cold front will cross the waters Saturday. SCA conditions are possible for portions of the waters during this time. && .TIDES/COASTAL FLOODING... Water level departures have eased to around a half foot. No additional inundation anticipated at this time, though may have to monitor mid to late week as southerly flow resumes. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && SYNOPSIS...HTS NEAR TERM...ADS/HTS SHORT TERM...HTS LONG TERM...HSK AVIATION...ADS/HSK/HTS MARINE...HSK/HTS TIDES/COASTAL FLOODING...HTS/ADS
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 509 AM EDT Tue Aug 1 2017 ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-020915- 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- 509 AM EDT Tue Aug 1 2017 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...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Wednesday through Monday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053- 055-501>506-020915- 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- 509 AM EDT Tue Aug 1 2017 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...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Wednesday through Monday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Sterling radar (KLWX), 46 km away, was scanning. The volume nearest the first event began at 18:01 UTC.
2 thunderstorm wind. Local standard time, as filed.
A tree fell onto a vehicle near the intersection of Farmbrook Drive and Brace Court. Several other trees were down in the area.
Wires and a pole were down near the intersection of Piney Branch Road and Sligo Creek Parkway.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2017Every state in 2017This day in weather historyWarnings in Maryland, August 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: 716536, 716537.