A hot and humid airmass along with a slow moving boundary led to some showers and thunderstorms. Weak winds aloft caused storms to move slowly, and this led to some instances of flooding and flash flooding.
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 hot and humid airmass along with a slow moving boundary led to some showers and thunderstorms. Weak winds aloft caused storms to move slowly, and this led to some instances of flooding and flash flooding.
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 Jul 23, 8:03 PM EST, 2 minutes earlier.
Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 903 PM EDT Thu Jul 23 2020 .SYNOPSIS... A cold front will drop south across our region late Friday. High pressure will then dominate over the weekend before a warm front advances back northward across the region on Monday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Main shortwave trough remains near the upper Ohio Valley, while a weaker perturbation may be near the local area. Earlier, a broken line of convection slowly moved east from the mountains while other storms developed over southeast Virginia. The outflows from these areas of convection are currently colliding across the Washington DC metro. Mesoanalysis shows 2000+ J/kg of MUCAPE, precipitable water greater than 2 inches, deep warm cloud layers, and weak flow (augmented by variable winds from the outflows). Since it became evident this would occur across the metro area, where flash flood guidance is 1-1.5 inches across most of the area, though those values could easily be exceeded, leading to at least localized flash flooding. Therefore hoisted a small short-fused Flash Flood Watch. The only uncertainty is what happens to the storms after they develop and where they move (or collapse). However, radar/satellite trends over the past 30 minutes are seeming to verify there will at least be a short term flooding threat. There could still be a brief severe threat with any stronger updrafts with locally damaging winds. Elsewhere, convection is generally trending downward. However, many models show a persisting threat of showers (and perhaps a few thunderstorms) lasting into the night. Since a lot of the area has seen showers or storms this evening, and instability is expected to generally decrease, don't think convection will be strong... although HRRR simulated reflectivity has been showing the potential for stronger cells. Patchy fog may form where it has rained and if there is sufficient clearing. Overnight lows will range from the mid 60s to mid 70s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... A cold front will push across the region on Friday. Until then, additional showers and thunderstorms will develop late Friday morning and Friday afternoon. Severe threat is substantially lower as well, but non-zero, particularly over southern MD. Marginal risk out from SPC for this area, with damaging winds the primary threat. Showers and thunderstorms should move to our south Friday evening. High pressure will build in Friday night. High temperatures on Friday will be in the upper 80s/low 90s, and perhaps slightly less humid as well. As a result, don't see any need for any heat headlines on Friday at this point. Dry weather is expected for most of the area. Lows will be slightly cooler than Thursday nights lows, with readings in the mid 60s to low 70s. High pressure will be building in from the west Saturday. However, there may be a bit of surface troughing remaining, and some guidance shows some isolated convection developing, mainly along the terrain. Temperatures will generally be seasonable, with highs in the low 90s. Humidity will be slightly lower too in the wake of the cold front, so again not expecting heat headlines on Saturday. Dry conditions continue into Saturday night with lows in the same range as Friday night. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Drier conditions should prevail during the later part of the weekend on Sunday with a strong upper level ridge building in from the Great Plains and Midwest. Hot and humid conditions will return in the early part of next week bringing in a consecutive round of chances for showers and storms through Wednesday with any type of shortwave energy that finds its way into our CWA. Most model guidance favors a fairly dry Monday leading to a wet pattern starting up Tuesday afternoon and evening with a cold front linked to an upper level trough north of the Canadian border. This will progress into early Wednesday with the afternoon and evening hours drying out with high pressure starting to build back in. Hot and humid conditions will build back in on Sunday allowing for temperatures to reach the low to mid 90s with heat index values potentially reaching triple digits through Tuesday with a very warm air mass overhead. Heat advisories will be possible Sunday through Tuesday. Cold front passage Tuesday night into Wednesday will bring the temperatures down to seasonal averages with lower humidity added in, trends are working more in favor for this later in the week but still early in the forecast. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... Heavy thunderstorms near KDCA this evening. A little bit uncertain as to what transpires moving forward with counteracting forces between an approaching disturbance and areas which have already been "worked over" by thunderstorms. Have kept some mention of precip in the TAFs through 04-06Z, though there could certainly be some showers and maybe an isolated storm the second half of the night. Kept a mention of MVFR BR at MRB and CHO, though relatively overcast skies most of the night may prevent much fog from forming. Guidance hints some MVFR ceilings may develop Friday morning for a few hours near MRB/IAD/BWI/MTN. Scattered storms will be possible again Friday as a front drops through, though coverage and intensity should be less. Patchy fog is possible again Friday night. Saturday should be a drier day overall, though there could still be an isolated shower or storm. No significant impacts expected for terminals Sunday through Monday. Isolated sub-VFR conditions possible early Tuesday with any storms that initialize in the area. && .MARINE... Light winds continue through Saturday, except near any thunderstorms. A threat of storms will linger through tonight and into Friday, though coverage may be a bit less by Friday afternoon than in recent days. Drier weather is more likely Saturday. Conditions are not expected to reach SCA criteria at this time Sunday and Monday with a weak disturbance bringing a few showers and storms to the area. Could see an isolated marine hazard be issued for any adjacent storms along the bay. && .CLIMATE... Aside from the one day last week that broke the streak of consecutive 90+ F days at Ronald Reagan Washington National Airport (KDCA), every day this month has had a high of at least 90 F. As of Thursday afternoon, that total (for July) was up to 22 days. The most 90+ F days ever in any month in the immediate Washington, DC, area is 25 days (set in July 2011). Looking at the pattern over the next 7 days, as well as probabilities for above normal temperatures from our colleagues at the Climate Prediction Center (CPC) out to 14 days, it seems it will be very difficult to NOT break that record. For the Baltimore, Maryland, and Dulles, Virginia long-term climate records, the record most 90+ F days in a month is 24 days (also set in July 2011). As of Wednesday afternoon, Baltimore site had hit 90 F 18 times so far this month, and the Dulles site had hit 90 F 16 days. Temperature records have been kept at what is now KDCA since 1941. The official temperature records for the immediate Washington, DC, area consist of data from KDCA starting in 1945, and observations taken in downtown Washington, DC, extend the region's period of record back to 1872. Temperature records for the Baltimore, Maryland, area have been kept at what is now Baltimore-Washington International Thurgood Marshall Airport (KBWI) since 1950. Additional temperature records observed in downtown Baltimore extend the period of record back to 1872. Temperature records for the Sterling-Dulles, Virginia, area have been kept at what is now Washington Dulles International Airport (KIAD) since 1960. All climate data are considered preliminary until reviewed by the National Centers for Environmental Information (NCEI). && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Flash Flood Watch until 2 AM EDT Friday for DCZ001. MD...Flash Flood Watch until 2 AM EDT Friday for MDZ013-504. VA...Flash Flood Watch until 2 AM EDT Friday for VAZ052>054. WV...None. MARINE...None. && SYNOPSIS...CJL NEAR TERM...ADS/KLW SHORT TERM...KLW LONG TERM...ADM AVIATION...ADS/KLW/ADM MARINE...KLW/ADM CLIMATE...LWX
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 815 PM EDT Thu Jul 23 2020 ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-250015- 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- 815 PM EDT Thu Jul 23 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...Tonight A Flash Flood Watch is in effect for the Washington DC Metropolitan Area until 2 AM. Scattered thunderstorms this afternoon could produce isolated damaging wind gusts and heavy rainfall, leading to isolated instances of flash flooding. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Heat indices near or above 105 degrees are possible on Monday and Tuesday. .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>506-250015- 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- 815 PM EDT Thu Jul 23 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...Tonight Scattered thunderstorms this afternoon could produce isolated damaging wind gusts and heavy rainfall, leading to isolated instances of flash flooding. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Heat indices near or above 100 degrees are possible on Monday and Tuesday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
533 PM EDT THU JUL 23 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0357 PM TSTM WND DMG 1 ENE TOWN CREEK 39.53N 78.52W
07/23/2020 ALLEGANY MD 911 CALL CENTER
TREE DAMAGE REPORTED NEAR OLD TOWN, INCLUDING ON MD-51
OLDTOWN ROAD SOUTHEAST NEAR CRABTREE LANE.
&&
EVENT NUMBER LWX2001666
DHPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
701 PM EDT THU JUL 23 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0624 PM TSTM WND DMG 3 E NORTH GARDEN 37.94N 78.59W
07/23/2020 ALBEMARLE VA 911 CALL CENTER
SEVERAL TREES BLOWN DOWN IN THE NORTH GARDEN AREA.
0638 PM TSTM WND DMG 1 ESE GLENDOWER 37.83N 78.53W
07/23/2020 ALBEMARLE VA 911 CALL CENTER
SEVERAL TREES DOWN NEAR SCOTTSVILLE.
0640 PM TSTM WND DMG 3 ENE OVERTON 37.97N 78.42W
07/23/2020 ALBEMARLE VA 911 CALL CENTER
SEVERAL TREES DOWN SOUTHEAST OF THE CITY OF
CHARLOTTESVILLE.
&&
EVENT NUMBER LWX2001667
EVENT NUMBER LWX2001668
EVENT NUMBER LWX2001669
DHPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
705 PM EDT THU JUL 23 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0704 PM MARINE TSTM WIND 2 SE COBB ISLAND 38.24N 76.83W
07/23/2020 M43 MPH ANZ537 MD BUOY
&&
EVENT NUMBER LWX2001670
DHPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
720 PM EDT THU JUL 23 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0719 PM MARINE TSTM WIND 2 SE COBB ISLAND 38.24N 76.83W
07/23/2020 M44 MPH ANZ537 MD BUOY
&&
EVENT NUMBER LWX2001671
DHPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
756 PM EDT THU JUL 23 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0750 PM MARINE TSTM WIND 2 E WOODBRIDGE 38.64N 77.22W
07/23/2020 M43 MPH ANZ536 VA BUOY
&&
EVENT NUMBER LWX2001672
BKFThe Sterling radar (KLWX), 41 km away, was scanning. The volume nearest the first event began at 01:05 UTC.
3 flood, 1 flash flood. Local standard time, as filed.
US Route 1 (Jefferson Davis Highway) was closed due to flooding at Gordon Boulevard and Marys Way.
Spotter reported knee high water pooling over sidewalks/curbs at intersection of Mount Vernon and East Maple Street. Road was impassable.
Several vehicles were submerged in high water on Cherry Hill Road near the CSX railroad tracks. Water rescues were required.
US Route 50 (Arlington Boulevard) ramp to Virginia Route 120 (Glebe Road) was closed due to flooding.
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, July 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: 912504, 912505, 912503, 912506.