Alert archive / Virginia / Flash Flood Warnings in 2020
Flash Flood Warning 63, NWS Baltimore/Washington
NWS Baltimore/Washington issued this flash flood warning at Sep 10, 2020, 1:28 PM EDT for Arlington County, Fairfax County, City of Alexandria, Virginia; Montgomery County, Prince George's County, Maryland. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.
The area
The counties it named.
The facts
- Issued
- Sep 10, 2020, 1:28 PM EDT (17:28 UTC)
- Expired
- Sep 10, 2020, 4:14 PM EDT
- In force
- 3 hr
- Issued by
- NWS Baltimore/Washington
- Area
- Storm-based polygon
- Flood severity
- None
Counties Montgomery County, MD, Prince George's County, MD, Arlington County, VA, City of Alexandria, VA, Fairfax County, VA
The radar
The Sterling radar (KLWX), 35 km from the middle of the area, began a volume at 17:30 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Wallops Is Stn, VA (KWAL), launched 12:00Z, 5.5 hours before the alert went out and 183 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 1088 J/kg
- Mixed-layer CIN
- -15 J/kg
- Mixed-layer LCL
- 575 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 142 m²/s²
- 0-3 km storm-relative helicity
- 167 m²/s²
- Significant tornado parameter
- 0.5
- Supercell composite
- 3.9
What forecasters said that day
The local office's own words before this flash flood warning went out, 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 this flash flood warning went out at Sep 10, 9:40 AM EDT, 3 hours 48 minutes earlier.
Area forecast discussion, Sep 10, 9:40 AM EDT, 3 hours 48 minutes before
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</html>Hazardous weather outlook, Sep 10, 5:00 AM EDT, 8 hours 28 minutes before
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 500 AM EDT Thu Sep 10 2020 ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-111000- 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- 500 AM EDT Thu Sep 10 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...Today and Tonight A Flash Flood Watch remains in effect for the outlook area through 8 PM this evening. Heavy rainfall from showers and thunderstorms may lead to instances of flash flooding during this time. An isolated waterspout cannot be ruled out over the waters this morning. .DAYS TWO THROUGH SEVEN...Friday through Wednesday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Please send any reports of flooding to the National Weather Service. MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053- 055-501>506-111000- 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- 500 AM EDT Thu Sep 10 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...Today and Tonight A Flash Flood Watch remains in effect for eastern Montgomery and eastern Howard Counties through 8 PM this evening. Elsewhere east of the Blue Ridge and Catoctin Mountains, locally heavy rainfall may lead to isolated instances of flooding. .DAYS TWO THROUGH SEVEN...Friday through Wednesday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Please send any reports of flooding to the National Weather Service.
In the hours before
Local storm report, Sep 10, 7:30 AM EDT, 5 hours 58 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
730 AM EDT THU SEP 10 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0706 AM FLASH FLOOD 1 SE CLEMENTS 38.31N 76.71W
09/10/2020 ST. MARYS MD 911 CALL CENTER
BAYSIDE ROAD WAS CLOSED DUE TO HIGH WATER.
&&
EVENT NUMBER LWX2002434
BJLLocal storm report, Sep 10, 7:42 AM EDT, 5 hours 46 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
742 AM EDT THU SEP 10 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0628 AM FLASH FLOOD CHAPTICO 38.37N 76.78W
09/10/2020 ST. MARYS MD 911 CALL CENTER
BUDDS CREEK ROAD WAS CLOSED DUE TO HIGH WATER NEAR
CHAPTICO.
&&
EVENT NUMBER LWX2002435
BJLLocal storm report, Sep 10, 7:45 AM EDT, 5 hours 43 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
745 AM EDT THU SEP 10 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0715 AM FLASH FLOOD 1 SW CHAPTICO 38.35N 76.80W
09/10/2020 ST. MARYS MD 911 CALL CENTER
MADDOX ROAD WAS CLOSED DUE TO HIGH WATER NEAR CHAPTICO.
&&
EVENT NUMBER LWX2002436
BJLLocal storm report, Sep 10, 9:27 AM EDT, 4 hours 1 minute before
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</html>Local storm report, Sep 10, 11:22 AM EDT, 2 hours 6 minutes before
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</html>Local storm report, Sep 10, 1:21 PM EDT, 7 minutes before
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</html>The office that day
Everything else NWS Baltimore/Washington issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 10, 12:03 AM EDT | Areal Flood Warning | LWX | Fairfax | 3 hr |
| Sep 10, 2:09 AM EDT | Areal Flood Warning | LWX | Fairfax | 83 min |
| Sep 10, 4:05 AM EDT | Areal Flood Warning | LWX | Fauquier, Frederick, Warren | 4 hr |
| Sep 10, 7:40 AM EDT | Special Marine Warning | LWX | 37 min | |
| Sep 10, 12:54 PM EDT | Areal Flood Warning | LWX | Clarke, Frederick | 2 hr |
| Sep 10, 4:14 PM EDT | Areal Flood Warning | LWX | Arlington, Fairfax, City of Alexandria | 9 hr |
| Sep 10, 4:18 PM EDT | Special Marine Warning | LWX | 54 min | |
| Sep 10, 4:37 PM EDT | Special Marine Warning | LWX | 22 min | |
| Sep 10, 4:35 AM EDT | Flash Flood Warning | LWX | Saint Mary's | 4 hr |
| Sep 10, 6:33 AM EDT | Flash Flood Warning | LWX | Charles | 2 hr |
| Sep 10, 8:21 AM EDT | Areal Flood Warning | LWX | Charles, Saint Mary's | 7 hr |
| Sep 10, 8:35 AM EDT | Areal Flood Warning | LWX | Saint Mary's | 8 hr |
| Sep 10, 12:41 PM EDT | Flash Flood Warning | LWX | Montgomery | 4 hr |
| Sep 10, 2:01 PM EDT | Areal Flood Warning | LWX | Charles | 3 hr |
| Sep 10, 2:34 PM EDT | Flash Flood Warning | LWX | Prince George's | 2 hr |
| Sep 10, 3:47 PM EDT | Flash Flood Warning | LWX | Charles, Saint Mary's | 3 hr |
| Sep 10, 4:33 PM EDT | Areal Flood Warning | LWX | Calvert, Charles, Prince George's | 5 hr |
| Sep 10, 4:37 PM EDT | Areal Flood Warning | LWX | Prince George's | 4 hr |
| Sep 10, 6:37 PM EDT | Areal Flood Warning | LWX | Charles, Saint Mary's | 4 hr |
Nearby
Flash Flood Warnings in Virginia, 2020Flash Flood Warnings in Maryland, 2020Every flash flood warning in 2020
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.