Alert archive / Maryland / Flash Flood Warnings in 2021

Flash Flood Warning 37, NWS Baltimore/Washington

August 14, 2021Calvert County, Charles County, Prince George's County, Maryland

NWS Baltimore/Washington issued this flash flood warning at Aug 14, 2021, 10:44 PM EDT for Calvert County, Charles County, Prince George's County, Maryland. It was in force for 3 hr. 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 14, 2021, 10:44 PM EDT (02:44 UTC)
Expired: Aug 15, 2021, 1:25 AM EDT
In force: 3 hr
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties Calvert County, MD, Charles County, MD, Prince George's County, MD

The radar

The Sterling radar (KLWX), 81 km from the middle of the area, began a volume at 02:43 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 14, 11:30 PM EDT	FLASH FLOOD	2 Wnw Dares Beach, MD	MPING: RIVER/CREEK OVERFLOWING; CROPLAND/YARD/BASEMENT FLOODING.

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, 2.7 hours before the alert went out and 73 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: 544 J/kg
Mixed-layer CIN: -2 J/kg
Mixed-layer LCL: 1447 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 3 m²/s²
0-3 km storm-relative helicity: 70 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

827 
WGUS51 KLWX 150244
FFWLWX
MDC009-017-033-150545-
/O.NEW.KLWX.FF.W.0037.210815T0244Z-210815T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
1044 PM EDT Sat Aug 14 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  Southeastern Prince Georges County in central Maryland...
  West Central Calvert County in southern Maryland...
  Charles County in southern Maryland...

* Until 145 AM EDT.

* At 1044 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...
  Waldorf...                         Prince Frederick...
  Breezy Point...                    Saint Charles...
  Huntingtown...                     Hughesville...
  Baden...                           Aquasco...
  Bryantown...                       Eagle Harbor...
  Barstow...                         Dares Beach...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3863 7667 3863 7651 3850 7649 3853 7667
      3854 7669 3854 7670 3853 7668 3855 7689
      3858 7691 3862 7689

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

$$

BKF

2 follow-up statements

289 
WGUS71 KLWX 150344
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
1144 PM EDT Sat Aug 14 2021

MDC009-017-033-150545-
/O.CON.KLWX.FF.W.0037.000000T0000Z-210815T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Calvert MD-Charles MD-Prince Georges MD-
1144 PM EDT Sat Aug 14 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 145 AM EDT SUNDAY FOR 
SOUTHEASTERN PRINCE GEORGES, WEST CENTRAL CALVERT AND CHARLES 
COUNTIES...

At 1144 PM EDT, Doppler radar and automated rain gauges indicated 
thunderstorms producing heavy rain across the warned area. Between 3 
and 5 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 and automated gauges.

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

Some locations that will experience flash flooding include...
  Waldorf...                         Prince Frederick...
Breezy Point...                    Saint Charles...
Huntingtown...                     Hughesville...
Baden...                           Aquasco...
Bryantown...                       Eagle Harbor...
Barstow...                         Dares Beach...

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 3863 7667 3863 7651 3850 7649 3853 7667
      3854 7669 3854 7670 3853 7668 3855 7689
      3858 7691 3862 7689

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

$$

BKF

353 
WGUS71 KLWX 150525
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
125 AM EDT Sun Aug 15 2021

MDC009-017-033-150535-
/O.CAN.KLWX.FF.W.0037.000000T0000Z-210815T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Calvert MD-Charles MD-Prince Georges MD-
125 AM EDT Sun Aug 15 2021

...FLASH FLOOD WARNING FOR SOUTHEASTERN PRINCE GEORGES, WEST CENTRAL 
CALVERT AND CHARLES COUNTIES HAS BEEN REPLACED WITH A FLOOD 
WARNING...

LAT...LON 3863 7667 3863 7651 3850 7649 3853 7667
      3854 7669 3854 7670 3853 7668 3855 7689
      3858 7691 3862 7689

$$

BKF

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 14, 10:28 PM EDT	Severe Thunderstorm Warning	LWX	Calvert, Charles, Prince George's	47 min
Aug 14, 11:54 PM EDT	Areal Flood Warning	LWX	Calvert, Charles, Saint Mary's	4 hr
Aug 15, 12:13 AM EDT	Flash Flood Warning Considerable damage threat	LWX	Prince George's	3 hr
Aug 15, 12:42 AM EDT	Flash Flood Warning Considerable damage threat	LWX	Montgomery, Prince George's	2 hr
Aug 15, 1:25 AM EDT	Areal Flood Warning	LWX	Calvert, Charles, Prince George's	2 hr
Aug 15, 5:47 PM EDT	Flash Flood Watch	LWX	Charles	18 hr

Nearby

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