Alert archive / Maryland / Flash Flood Warnings in 2021
Flash Flood Warning 52, NWS Baltimore/Washington
NWS Baltimore/Washington issued this flash flood warning at Aug 20, 2021, 8:21 AM EDT for Montgomery County, Prince George's County, Maryland. It was in force for 101 min. 1 report 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, 8:21 AM EDT (12:21 UTC)
- Expired
- Aug 20, 2021, 10:02 AM EDT
- In force
- 101 min
- Issued by
- NWS Baltimore/Washington
- Area
- Storm-based polygon
- Damage threat
- Considerable
- Flood severity
- None
The radar
The Sterling radar (KLWX), 42 km from the middle of the area, began a volume at 12:25 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, 9:15 AM EDT | FLOOD | 1 Sw Four Corners, MD | SLIGO CREEK PARKWAY CLOSED AT BRUNETT AVENUE DUE TO STANDING HIGH WATER IN 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 12:00Z, 0.4 hours before the alert went out and 35 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
- 106 J/kg
- Mixed-layer CIN
- -34 J/kg
- Mixed-layer LCL
- 644 m above ground
- 0-6 km bulk shear
- 8 kt
- 0-1 km storm-relative helicity
- -39 m²/s²
- 0-3 km storm-relative helicity
- 41 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
021
WGUS51 KLWX 201221
FFWLWX
DCC001-MDC031-033-201645-
/O.NEW.KLWX.FF.W.0052.210820T1221Z-210820T1645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
821 AM EDT Fri Aug 20 2021
The National Weather Service in Sterling Virginia has issued a
* Flash Flood Warning for...
Northeastern District of Columbia...
Southeastern Montgomery County in central Maryland...
Northwestern Prince Georges County in central Maryland...
* Until 1245 PM EDT.
* At 821 AM EDT, Doppler radar indicated heavy rain across the
warned area. Between 1.5 and 2.5 inches of rain have fallen.
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. 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...
College Park... Langley Park...
Beltsville... Fairland...
Hyattsville... White Oak...
Takoma Park... Adelphi...
Colesville... Kemp Mill...
North Kensington... Forest Glen...
Hillandale... Wheaton-Glenmont...
Silver Spring... Wheaton...
Chillum... Calverton...
Glenmont... Mount Rainier...
This includes the following streams and drainages...
Sligo Creek, Rock Creek and Anacostia River.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
Be aware of your surroundings and do not drive on flooded roads.
&&
LAT...LON 3901 7705 3907 7707 3907 7705 3906 7702
3906 7699 3904 7696 3901 7696 3896 7695
3893 7696 3893 7697 3895 7699 3897 7702
3899 7705
FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
$$
JMG1 follow-up statement
209
WGUS71 KLWX 201402
FFSLWX
Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
1002 AM EDT Fri Aug 20 2021
DCC001-MDC031-033-201412-
/O.CAN.KLWX.FF.W.0052.000000T0000Z-210820T1645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia DC-Montgomery MD-Prince Georges MD-
1002 AM EDT Fri Aug 20 2021
...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHEASTERN MONTGOMERY AND
NORTHWESTERN PRINCE GEORGES COUNTIES AND THE NORTHEASTERN DISTRICT
OF COLUMBIA...
The heavy rain has ended but light rain continues. Flooding is
ongoing but the threat for the rapid rise in water levels have
ended. Please continue to heed road closures.
An Areal Flood Warning remains in effect until 1:45pm this afternoon
A Flash Flood Watch remains in effect until 1200 PM EDT for portions
of DC, central Maryland and northern Virginia.
LAT...LON 3901 7705 3907 7707 3907 7705 3906 7702
3906 7699 3904 7696 3901 7696 3896 7695
3893 7696 3893 7697 3895 7699 3897 7702
3899 7705
$$
JMGThe office that day
Everything else NWS Baltimore/Washington issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 20, 4:52 AM EDT | Flash Flood Warning | LWX | Frederick | 102 min |
| Aug 20, 6:34 AM EDT | Areal Flood Warning | LWX | Frederick | 2 hr |
| Aug 20, 7:35 AM EDT | Areal Flood Warning | LWX | Montgomery, Prince George's | 9 hr |
| Aug 20, 7:55 AM EDT | Flash Flood Warning | LWX | Montgomery | 2 hr |
| Aug 20, 8:16 AM EDT | Flash Flood Warning | LWX | Montgomery | 111 min |
| Aug 20, 11:20 AM EDT | Areal Flood Warning | LWX | Anne Arundel, Calvert | 3 hr |
Nearby
Flash Flood Warnings in Maryland, 2021Flash Flood Warnings in District of Columbia, 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.