Alert archive / Virginia / Flash Flood Warnings in 2021
Flash Flood Warning 49, NWS Baltimore/Washington
NWS Baltimore/Washington issued this flash flood warning at Aug 20, 2021, 7:52 AM EDT for Fairfax County, Virginia. It was in force for 2 hr. 7 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
- Aug 20, 2021, 7:52 AM EDT (11:52 UTC)
- Expired
- Aug 20, 2021, 10:05 AM EDT
- In force
- 2 hr
- Issued by
- NWS Baltimore/Washington
- Area
- Storm-based polygon
- Damage threat
- Considerable
- Flood severity
- None
County Fairfax County, VA
The radar
The Sterling radar (KLWX), 21 km from the middle of the area, began a volume at 11:52 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
| Time | Report | Where | Remark |
|---|---|---|---|
| Aug 20, 8:00 AM EDT | FLASH FLOOD | Stratmeade Springs, VA | ACCOTINK CREEK ROSE RAPIDLY OUT OF ITS BANKS. |
| Aug 20, 8:37 AM EDT | FLASH FLOOD | 1 S Merrifield, VA | US-50 ARLINGTON BOULEVARD CLOSED AT LONG BRANCH NEAR VA-699 PROSPERITY AVENUE. WATER FLOWING OUT OF CREEK ACROSS ENTIRE ROADWAY. |
| Aug 20, 8:37 AM EDT | FLASH FLOOD | 2 Se Wolf Trap, VA | WATER RESCUE AT THE INTERSECTION OF VA-677 OLD COURTHOUSE ROAD AND BESLEY ROAD. |
| Aug 20, 9:10 AM EDT | FLOOD | 2 S Merrifield, VA | 3700 BLOCK OF PROSPERITY AVENUE CLOSED DUE TO HIGH WATER. |
| Aug 20, 9:10 AM EDT | FLOOD | 2 Wnw Annandale, VA | WOODBURN ROAD AT SPICEWOOD DRIVE CLOSED DUE TO HIGH WATER. |
| Aug 20, 9:10 AM EDT | FLOOD | Oakton, VA | HUNTER MILL ROAD CLOSED DUE TO HIGH WATER. |
| Aug 20, 9:10 AM EDT | FLASH FLOOD | 2 Sw Wolf Trap, VA | LAWYERS RUN ROAD CLOSED DUE TO DIFFICULT RUN FLOWING ACROSS THE ROAD. |
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, 11.9 hours before the alert went out and 13 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
- 652 J/kg
- Mixed-layer CIN
- -5 J/kg
- Mixed-layer LCL
- 1240 m above ground
- 0-6 km bulk shear
- 25 kt
- 0-1 km storm-relative helicity
- 14 m²/s²
- 0-3 km storm-relative helicity
- 36 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.4
The text
As transmitted.
291
WGUS51 KLWX 201152
FFWLWX
VAC059-201545-
/O.NEW.KLWX.FF.W.0049.210820T1152Z-210820T1545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
752 AM EDT Fri Aug 20 2021
The National Weather Service in Sterling Virginia has issued a
* Flash Flood Warning for...
North Central Fairfax County in northern Virginia...
* Until 1145 AM EDT.
* At 752 AM EDT, Doppler radar indicated heavy rain across the
warned area. Between 1 and 3 inches of rain have fallen. The
expected rainfall rate is 1 to 2 inches in 1 hour. Additional
rainfall amounts of 1 to 2 inches are possible in the warned area.
Flash flooding is already occurring.
HAZARD...Life threatening flash flooding. Heavy rain 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...
Annandale... Fairfax...
Vienna... Mantua...
Pimmit Hills... Oakton...
Tysons Corner... Wolf Trap...
Merrifield... I66 and I495 Interchange...
Dunn Loring... Belleview...
This includes the following Flood Prone Roads:
Woodburn Road at Accotink Creek...
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
&&
LAT...LON 3888 7732 3890 7733 3890 7732 3892 7732
3897 7726 3896 7723 3896 7721 3894 7720
3891 7719 3889 7720 3887 7720 3884 7721
3884 7727 3887 7726 3887 7729 3887 7730
3888 7731
FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR
$$
LFR2 follow-up statements
581
WGUS71 KLWX 201352
FFSLWX
Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
952 AM EDT Fri Aug 20 2021
VAC059-201545-
/O.CON.KLWX.FF.W.0049.000000T0000Z-210820T1545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Fairfax VA-
952 AM EDT Fri Aug 20 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1145 AM EDT THIS
MORNING FOR NORTH CENTRAL FAIRFAX COUNTY...
At 952 AM EDT, Doppler radar indicated heavy rain across the warned
area. Between 2 and 3 inches of rain have fallen. Additional
rainfall amounts up to 0.5 inches are possible in the warned area.
Multiple stream gauges have indicated rapid rises up to minor flood
stage along with multiple reports of flooding on Interstate 267 and
Route 50. Flash flooding is ongoing.
HAZARD...Life threatening flash flooding. Heavy rain producing
flash flooding.
SOURCE...Radar.
IMPACT...Life threatening flash flooding of creeks and streams,
urban areas, highways, streets and underpasses.
Some locations that will experience flash flooding include...
Annandale... Fairfax...
Vienna... Mantua...
Pimmit Hills... Oakton...
Tysons Corner... Wolf Trap...
Merrifield... I66 and I495 Interchange...
Dunn Loring... Belleview...
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
&&
LAT...LON 3888 7732 3890 7733 3890 7732 3892 7732
3897 7726 3896 7723 3896 7721 3894 7720
3891 7719 3889 7720 3887 7720 3884 7721
3884 7727 3887 7726 3887 7729 3887 7730
3888 7731
FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
$$
JMG690
WGUS71 KLWX 201405
FFSLWX
Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
1005 AM EDT Fri Aug 20 2021
VAC059-201415-
/O.CAN.KLWX.FF.W.0049.000000T0000Z-210820T1545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Fairfax VA-
1005 AM EDT Fri Aug 20 2021
...FLASH FLOOD WARNING IS CANCELLED FOR NORTH CENTRAL FAIRFAX
COUNTY...
The heavy rain has ended but light rain continues. Flooding is
ongoing but the threat for the rapid rise in water levels have
ended. Please continue to heed road closures.
An Areal Flood Warning remains in effect until 1:15pm this afternoon
A Flash Flood Watch remains in effect until 1200 PM EDT for portions
of DC, central Maryland and northern Virginia.
LAT...LON 3888 7732 3890 7733 3890 7732 3892 7732
3897 7726 3896 7723 3896 7721 3894 7720
3891 7719 3889 7720 3887 7720 3884 7721
3884 7727 3887 7726 3887 7729 3887 7730
3888 7731
$$
JMGThe office that day
Everything else NWS Baltimore/Washington issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 19, 9:14 PM EDT | Special Marine Warning | LWX | 91 min | |
| Aug 19, 10:38 PM EDT | Special Marine Warning | LWX | 67 min | |
| Aug 20, 4:43 AM EDT | Flash Flood Warning | LWX | Madison | 91 min |
| Aug 20, 5:35 AM EDT | Special Marine Warning | LWX | 27 min | |
| Aug 20, 6:14 AM EDT | Areal Flood Warning | LWX | Madison | 6 hr |
| Aug 20, 7:18 AM EDT | Areal Flood Warning | LWX | Fairfax, City of Fairfax | 9 hr |
| Aug 20, 7:24 AM EDT | Small Craft Advisory | LWX | 5 hr | |
| Aug 20, 7:35 AM EDT | Areal Flood Warning | LWX | Arlington, Fairfax, City of Alexandria, City of Falls Church | 9 hr |
| Aug 20, 7:55 AM EDT | Flash Flood Warning | LWX | Arlington | 2 hr |
| Aug 20, 8:16 AM EDT | Flash Flood Warning | LWX | Arlington, Fairfax, City of Alexandria, City of Falls Church | 111 min |
| Aug 20, 8:39 AM EDT | Areal Flood Warning | LWX | King George, Spotsylvania, Stafford, City of Fredericksburg | 5 hr |
| Aug 20, 10:02 AM EDT | Special Marine Warning | LWX | 88 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.