Alert archive / Virginia / Flash Flood Warnings in 2020

Flash Flood Warning 38, NWS Baltimore/Washington

August 12, 20204 counties in Virginia

NWS Baltimore/Washington issued this flash flood warning at Aug 12, 2020, 4:07 AM EDT for 4 counties in Virginia. It was in force for 118 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Aug 12, 2020, 4:07 AM EDT (08:07 UTC)
Expired
Aug 12, 2020, 6:05 AM EDT
In force
118 min
Issued by
NWS Baltimore/Washington
Area
Storm-based polygon
Damage threat
Considerable
Flood severity
None

Counties City of Manassas, VA, City of Manassas Park, VA, Fairfax County, VA, Prince William County, VA

The radar

The Sterling radar (KLWX), 24 km from the middle of the area, began a volume at 08:08 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

Washington/Dulle, VA (KIAD), launched 00:00Z, 8.1 hours before the alert went out and 20 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.

Skew-T log-pSkew-T log-p diagram, Washington/Dulle, VA at 00:00Z on 2020-08-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1124 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2020-08-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 24 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
1124 J/kg
Mixed-layer CIN
-15 J/kg
Mixed-layer LCL
1414 m above ground
0-6 km bulk shear
14 kt
0-1 km storm-relative helicity
24 m²/s²
0-3 km storm-relative helicity
88 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

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 Aug 11, 9:25 PM EDT, 6 hours 42 minutes earlier.

Area forecast discussion, Aug 11, 9:25 PM EDT, 6 hours 42 minutes before
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Hazardous weather outlook, Aug 11, 3:25 PM EDT, 12 hours 42 minutes before
Hazardous Weather Outlook
National Weather Service Baltimore MD/Washington DC
325 PM EDT Tue Aug 11 2020

ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-121000-
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-
325 PM EDT Tue Aug 11 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

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

A Flash Flood Watch is in effect from Wednesday afternoon through
Wednesday evening.

Showers and thunderstorms are likely Thursday through Saturday,
some of which will produce locally heavy rainfall. A few storms
could cause isolated instances of flash flooding.

.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>506-121000-
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-
325 PM EDT Tue Aug 11 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

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

A Flash Flood Watch is in effect from Wednesday afternoon through
Wednesday evening.

Showers and thunderstorms are likely Thursday through Saturday,
some of which will produce locally heavy rainfall. A few storms
could cause isolated instances of flash flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

The office that day

Everything else NWS Baltimore/Washington issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 11, 9:16 PM EDTSevere Thunderstorm WarningLWXAlbemarle, Greene, Rockingham30 min
Aug 12, 2:01 AM EDTAreal Flood WarningLWXGreene, Madison, Rockingham4 hr
Aug 12, 3:30 AM EDTAreal Flood WarningLWXNelson6 hr
Aug 12, 3:55 AM EDTAreal Flood WarningLWXFairfax, Prince William, City of Manassas, City of Manassas Park8 hr
Aug 12, 6:05 AM EDTAreal Flood WarningLWXFairfax, Prince William6 hr
Aug 12, 6:19 AM EDTAreal Flood WarningLWXFairfax8 hr
Aug 12, 7:21 AM EDTFlash Flood Warning Considerable damage threatLWXPrince William109 min
Aug 12, 2:08 PM EDTSpecial Marine WarningLWX22 min
Aug 12, 2:22 PM EDTSpecial Marine WarningLWX31 min
Aug 12, 5:10 PM EDTSpecial Marine WarningLWX60 min
Aug 12, 5:27 PM EDTSpecial Marine WarningLWX63 min
Aug 12, 5:39 PM EDTSpecial Marine WarningLWX32 min
Aug 12, 5:49 PM EDTSevere Thunderstorm WarningLWXHighland41 min
Aug 12, 6:26 PM EDTFlash Flood Warning Considerable damage threatLWXAlbemarle, Nelson4 hr
Aug 12, 6:37 PM EDTSpecial Marine WarningLWX83 min
Aug 12, 6:54 PM EDTFlash Flood Warning Considerable damage threatLWXFairfax, Loudoun2 hr
Aug 12, 7:08 PM EDTAreal Flood WarningLWXAlbemarle, Augusta, Rockingham, City of Waynesboro3 hr
Aug 12, 7:22 PM EDTSpecial Marine WarningLWX56 min
Aug 12, 7:53 PM EDTAreal Flood WarningLWXLoudoun2 hr
Aug 12, 1:30 PM EDTAreal Flood WarningLWXBaltimore, Howard57 min
Aug 12, 4:23 PM EDTFlash Flood Warning Considerable damage threatLWXHarford3 hr
Aug 12, 4:54 PM EDTSevere Thunderstorm WarningLWXAnne Arundel36 min
Aug 12, 5:05 PM EDTSevere Thunderstorm WarningLWXAnne Arundel, Baltimore, Howard40 min
Aug 12, 5:13 PM EDTFlash Flood Warning Considerable damage threatLWXAnne Arundel4 hr
Aug 12, 5:23 PM EDTSevere Thunderstorm WarningLWXBaltimore, Howard, City of Baltimore38 min
Aug 12, 5:35 PM EDTAreal Flood WarningLWXBaltimore, Howard, City of Baltimore7 hr
Aug 12, 5:42 PM EDTFlash Flood Warning Considerable damage threatLWXBaltimore, Howard, City of Baltimore3 hr
Aug 12, 5:49 PM EDTFlash Flood Warning Considerable damage threatLWXHoward, Montgomery, Prince George's3 hr
Aug 12, 6:10 PM EDTFlash Flood Warning Considerable damage threatLWXAnne Arundel, Baltimore, City of Baltimore3 hr
Aug 12, 6:50 PM EDTAreal Flood WarningLWXFrederick108 min

Nearby

Flash Flood Warnings in Virginia, 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.