Alert archive / Maryland / Flash Flood Warnings in 2021

Flash Flood Warning 23, NWS Baltimore/Washington

July 8, 2021Saint Mary's County, Maryland

NWS Baltimore/Washington issued this flash flood warning at Jul 8, 2021, 11:13 PM EDT for Saint Mary's County, Maryland. It was in force for 76 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
Jul 8, 2021, 11:13 PM EDT (03:13 UTC)
Expired
Jul 9, 2021, 12:29 AM EDT
In force
76 min
Issued by
NWS Baltimore/Washington
Area
Storm-based polygon
Damage threat
Considerable
Flood severity
None

County Saint Mary's County, MD

The radar

The Dover AFB radar (KDOX), 113 km from the middle of the area, began a volume at 03:15 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

Wallops Is Stn, VA (KWAL), launched 00:00Z, 3.2 hours before the alert went out and 95 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, Wallops Is Stn, VA at 00:00Z on 2021-07-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 440 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Wallops Is Stn, VA at 00:00Z on 2021-07-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 151 square meters per square second.19395878Sfc1 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
440 J/kg
Mixed-layer CIN
-10 J/kg
Mixed-layer LCL
675 m above ground
0-6 km bulk shear
42 kt
0-1 km storm-relative helicity
151 m²/s²
0-3 km storm-relative helicity
336 m²/s²
Significant tornado parameter
0.3
Supercell composite
3.3

Open this sounding in Storm Lab

The text

As transmitted.

865 
WGUS51 KLWX 090313
FFWLWX
MDC037-090615-
/O.NEW.KLWX.FF.W.0023.210709T0313Z-210709T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
1113 PM EDT Thu Jul 8 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  Southeastern St. Marys County in southern Maryland...

* Until 215 AM EDT.

* At 1113 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 within 1 hour. 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...
  Lexington Park...                  Piney Point...
  Tall Timbers...                    Saint Marys City...
  Saint Marys River...               Saint Inigoes Creek...
  Saint George Island...             Saint Inigoes...
  Park Hall...                       Drayden...
  Dameron...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3816 7654 3818 7651 3818 7652 3819 7651
      3821 7649 3823 7647 3825 7644 3825 7643
      3825 7638 3823 7638 3824 7637 3823 7636
      3817 7632 3815 7634 3811 7640 3810 7644
      3810 7643 3809 7644 3812 7653

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR

$$

BJL
1 follow-up statement
108 
WGUS71 KLWX 090429
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
1229 AM EDT Fri Jul 9 2021

MDC037-090439-
/O.CAN.KLWX.FF.W.0023.000000T0000Z-210709T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
St. Marys MD-
1229 AM EDT Fri Jul 9 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHEASTERN ST. MARYS 
COUNTY...

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

LAT...LON 3816 7654 3818 7651 3818 7652 3819 7651
      3821 7649 3823 7647 3825 7644 3825 7643
      3825 7638 3823 7638 3824 7637 3823 7636
      3817 7632 3815 7634 3811 7640 3810 7644
      3810 7643 3809 7644 3812 7653

$$

BJL

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 8, 10:31 PM EDTTornado WarningLWXSaint Mary's29 min
Jul 8, 11:13 PM EDTTornado WarningLWXCalvert, Saint Mary's17 min
Jul 9, 12:40 AM EDTCoastal Flood WarningLWXSaint Mary's2 hr
Jul 9, 12:47 AM EDTCoastal Flood AdvisoryLWXCharles2 hr
Jul 9, 4:56 PM EDTSevere Thunderstorm WarningLWXAnne Arundel, Prince George's49 min
Jul 9, 5:02 PM EDTAreal Flood WarningLWXPrince George's3 hr
Jul 9, 5:30 PM EDTSevere Thunderstorm WarningLWXCalvert, Charles, Prince George's45 min
Jul 9, 5:54 PM EDTSevere Thunderstorm WarningLWXCalvert51 min
Jul 9, 6:03 PM EDTSevere Thunderstorm WarningLWXCecil, Harford57 min
Jul 9, 6:17 PM EDTSevere Thunderstorm WarningLWXCharles, Prince George's31 min
Jul 9, 6:19 PM EDTSevere Thunderstorm WarningLWXCalvert, Charles, Prince George's, Saint Mary's41 min
Jul 9, 6:43 PM EDTSevere Thunderstorm WarningLWXCalvert32 min
Jul 9, 6:55 PM EDTSevere Thunderstorm WarningLWXCarroll, Frederick50 min
Jul 9, 7:05 PM EDTAreal Flood WarningLWXCalvert, Charles, Prince George's3 hr

Nearby

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