Alert archive / Virginia / Flash Flood Warnings in 2021

Flash Flood Warning 72, NWS Baltimore/Washington

September 16, 2021Fairfax County, City of Alexandria, Virginia

NWS Baltimore/Washington issued this flash flood warning at Sep 16, 2021, 5:31 PM EDT for Fairfax County, City of Alexandria, Virginia. It was in force for 67 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Sep 16, 2021, 5:31 PM EDT (21:31 UTC)
Expired: Sep 16, 2021, 6:38 PM EDT
In force: 67 min
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties City of Alexandria, VA, Fairfax County, VA

The radar

The Sterling radar (KLWX), 40 km from the middle of the area, began a volume at 21:33 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 12:00Z, 9.5 hours before the alert went out and 32 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 153 J/kg
Mixed-layer CIN: -184 J/kg
Mixed-layer LCL: 830 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: 43 m²/s²
0-3 km storm-relative helicity: 114 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

253 
WGUS51 KLWX 162131
FFWLWX
VAC059-510-170030-
/O.NEW.KLWX.FF.W.0072.210916T2131Z-210917T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
531 PM EDT Thu Sep 16 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  Southeastern Fairfax County in northern Virginia...
  The Southern City of Alexandria in northern Virginia...

* Until 830 PM EDT.

* At 531 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 3 inches of rain 
  have fallen. Additional rainfall amounts of 1 to 2 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Life threatening flash flooding. Thunderstorms
           producing flash flooding.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  Arlington...                       Alexandria...
  Groveton...                        Huntington...
  Hybla Valley...                    Jefferson Manor...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 3880 7713 3881 7712 3883 7710 3882 7704
      3881 7703 3879 7704 3877 7705 3876 7710
      3878 7712 3879 7713

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

MSS

1 follow-up statement

499 
WGUS71 KLWX 162238
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
638 PM EDT Thu Sep 16 2021

VAC059-510-162248-
/O.CAN.KLWX.FF.W.0072.000000T0000Z-210917T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Fairfax VA-City of Alexandria VA-
638 PM EDT Thu Sep 16 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHEASTERN FAIRFAX COUNTY 
AND THE SOUTHERN CITY OF ALEXANDRIA...

The heavy rain has ended. However a Flood Warning remains in effect. 
Please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 900 PM EDT for portions 
of DC, Maryland and northern Virginia.

LAT...LON 3880 7713 3881 7712 3883 7710 3882 7704
      3881 7703 3879 7704 3877 7705 3876 7710
      3878 7712 3879 7713

$$

MSS

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 15, 9:40 PM EDT	Special Marine Warning	LWX		95 min
Sep 16, 2:44 PM EDT	Flash Flood Watch	LWX	Arlington, Fairfax, Loudoun, City of Alexandria, City of Fairfax, City of Falls Church	6 hr
Sep 16, 3:21 PM EDT	Areal Flood Warning	LWX	Arlington, Fairfax, City of Alexandria, City of Fairfax, City of Falls Church	6 hr
Sep 16, 3:50 PM EDT	Flash Flood Warning Considerable damage threat	LWX	Arlington, Fairfax, City of Alexandria, City of Falls Church	3 hr
Sep 16, 4:31 PM EDT	Areal Flood Warning	LWX	Fairfax, Prince William, City of Manassas, City of Manassas Park	3 hr
Sep 16, 7:47 PM EDT	Small Craft Advisory	LWX		21 hr

Nearby

Flash Flood Warnings in Virginia, 2021 Every flash flood warning in 2021

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.