Alert archive / Virginia / Flash Flood Warnings in 2021

Flash Flood Warning 63, NWS Baltimore/Washington

September 1, 2021Fairfax County, Prince William County, City of Manassas Park, Virginia

NWS Baltimore/Washington issued this flash flood warning at Sep 1, 2021, 3:01 AM EDT for Fairfax County, Prince William County, City of Manassas Park, Virginia. It was in force for 2 hr. 2 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued
Sep 1, 2021, 3:01 AM EDT (07:01 UTC)
Expired
Sep 1, 2021, 5:08 AM EDT
In force
2 hr
Issued by
NWS Baltimore/Washington
Area
Storm-based polygon
Damage threat
Considerable
Flood severity
None

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

The radar

The Sterling radar (KLWX), 14 km from the middle of the area, began a volume at 07:00 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.

What was reported inside it

TimeReportWhereRemark
Sep 1, 4:26 AM EDTFLASH FLOOD1 Sw Wolf Trap, VAFLOODING AND STORM DEBRIS BLOCKED VA-674 HUNTER MILL ROAD BOTH WAYS AT DIFFICULT RUN RIVER BETWEEN CEDAR POND DRIVE AND VA-677 HUNTER STATION ROAD.
Sep 1, 4:48 AM EDTFLOODReston, VATWO CARS STRANDED IN HIGH WATER NEAR METRO CENTER DR.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 7.0 hours before the alert went out and 8 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 2021-09-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 723 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 2021-09-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 96 square meters per square second.193958Sfc1 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
723 J/kg
Mixed-layer CIN
-24 J/kg
Mixed-layer LCL
969 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
96 m²/s²
0-3 km storm-relative helicity
171 m²/s²
Significant tornado parameter
0.3
Supercell composite
2.7

Open this sounding in Storm Lab

The text

As transmitted.

502 
WGUS51 KLWX 010701
FFWLWX
VAC059-153-685-011000-
/O.NEW.KLWX.FF.W.0063.210901T0701Z-210901T1000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
301 AM EDT Wed Sep 1 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  Northwestern Fairfax County in northern Virginia...
  Prince William County in northern Virginia...
  The Northeastern City of Manassas Park in northern Virginia...

* Until 600 AM EDT.

* At 301 AM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 3 inches of rain 
  have fallen. The expected rainfall rate is 1.75 to 3 inches in 1 
  hour. Additional rainfall amounts of 0.5 to 1.5 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...
  Centreville...                     Reston...
  South Riding...                    Herndon...
  Fairfax...                         Oakton...
  Chantilly...                       Wolf Trap...
  Manassas Park...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3891 7748 3892 7744 3898 7736 3896 7731
      3893 7726 3887 7733 3886 7733 3886 7734
      3877 7742 3877 7745 3880 7747 3883 7754

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL...1.75-3 INCHES IN 1 HOUR

$$

JMG
1 follow-up statement
384 
WGUS71 KLWX 010908
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
508 AM EDT Wed Sep 1 2021

VAC059-153-685-010918-
/O.CAN.KLWX.FF.W.0063.000000T0000Z-210901T1000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Fairfax VA-Prince William VA-City of Manassas Park VA-
508 AM EDT Wed Sep 1 2021

...FLASH FLOOD WARNING IS CANCELLED FOR NORTHWESTERN FAIRFAX AND 
PRINCE WILLIAM COUNTIES AND THE NORTHEASTERN CITY OF MANASSAS PARK...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 800 AM EDT Thursday for 
portions of DC, Maryland and Virginia.

LAT...LON 3891 7748 3892 7744 3898 7736 3896 7731
      3893 7726 3887 7733 3886 7733 3886 7734
      3877 7742 3877 7745 3880 7747 3883 7754

$$

JMG

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 31, 9:44 PM EDTRiver Flood WatchLWXLoudoun25 hr
Aug 31, 9:44 PM EDTRiver Flood WatchLWXLoudoun48 hr
Aug 31, 9:44 PM EDTRiver Flood WatchLWXFairfax, City of Fairfax25 hr
Aug 31, 10:29 PM EDTTornado WarningLWXAlbemarle17 min
Aug 31, 10:39 PM EDTTornado WarningLWXAlbemarle, Nelson36 min
Aug 31, 10:58 PM EDTTornado WarningLWXAlbemarle, Nelson32 min
Aug 31, 11:13 PM EDTSevere Thunderstorm WarningLWXAlbemarle, Augusta, Nelson, City of Waynesboro47 min
Aug 31, 11:23 PM EDTTornado WarningLWXAlbemarle, City of Charlottesville37 min
Aug 31, 11:34 PM EDTAreal Flood WarningLWXAlbemarle, City of Charlottesville5 hr
Aug 31, 11:41 PM EDTFlash Flood Warning Considerable damage threatLWXAlbemarle, City of Charlottesville87 min
Aug 31, 11:49 PM EDTTornado WarningLWXAlbemarle, Augusta, Nelson, Rockingham, City of Waynesboro15 min
Aug 31, 11:56 PM EDTTornado WarningLWXAlbemarle34 min
Sep 1, 12:18 AM EDTSevere Thunderstorm WarningLWXCulpeper, Madison, Orange42 min
Sep 1, 12:25 AM EDTTornado WarningLWXCulpeper, Madison, Orange35 min
Sep 1, 12:53 AM EDTSevere Thunderstorm WarningLWXCulpeper, Fauquier, Orange52 min
Sep 1, 1:09 AM EDTSevere Thunderstorm WarningLWXCulpeper, Fauquier, Orange51 min
Sep 1, 1:42 AM EDTSevere Thunderstorm WarningLWXFauquier35 min
Sep 1, 2:25 AM EDTAreal Flood WarningLWXFairfax, Loudoun, Prince William, City of Manassas, City of Manassas Park11 hr
Sep 1, 2:34 AM EDTSevere Thunderstorm WarningLWXFairfax, City of Fairfax41 min
Sep 1, 2:52 AM EDTAreal Flood WarningLWXFairfax, City of Fairfax9 hr
Sep 1, 2:59 AM EDTSevere Thunderstorm WarningLWXArlington, Fairfax, City of Alexandria, City of Fairfax, City of Falls Church46 min
Sep 1, 3:08 AM EDTSpecial Marine WarningLWX67 min
Sep 1, 3:23 AM EDTAreal Flood WarningLWXArlington, Fairfax, City of Falls Church8 hr
Sep 1, 3:55 AM EDTSpecial Marine WarningLWX95 min
Sep 1, 4:34 AM EDTAreal Flood WarningLWXFairfax, Loudoun6 hr
Sep 1, 5:23 AM EDTSpecial Marine WarningLWX69 min
Sep 1, 11:42 AM EDTTornado WarningLWXCulpeper, Madison, Rappahannock12 min
Sep 1, 12:31 PM EDTAreal Flood WarningLWXPage, Rockingham, Shenandoah, Warren15 hr
Sep 1, 12:52 PM EDTSpecial Marine WarningLWX68 min
Sep 1, 12:55 PM EDTTornado WarningLWXKing George35 min
Sep 1, 1:23 PM EDTTornado WarningLWXKing George17 min
Sep 1, 1:30 PM EDTAreal Flood WarningLWXLoudoun27 hr
Sep 1, 2:05 PM EDTSpecial Marine WarningLWX55 min
Sep 1, 2:44 PM EDTSpecial Marine WarningLWX91 min
Sep 1, 2:48 PM EDTSpecial Marine WarningLWX87 min
Sep 1, 3:02 PM EDTSpecial Marine WarningLWX28 min
Sep 1, 3:28 PM EDTSmall Craft AdvisoryLWX44 hr
Sep 1, 3:36 PM EDTWind AdvisoryLWXGreene, Madison, Page, Rappahannock, Rockingham, Warren7 hr
Sep 1, 3:43 PM EDTSpecial Marine WarningLWX35 min
Sep 1, 4:52 PM EDTSpecial Marine WarningLWX23 min
Sep 1, 4:58 PM EDTSpecial Marine WarningLWX31 min

Nearby

Flash Flood Warnings in Virginia, 2021Every 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.