Alert archive / Maryland / Flash Flood Warnings in 2021

Flash Flood Warning 75, NWS Baltimore/Washington

September 23, 2021Frederick County, Washington County, Maryland

NWS Baltimore/Washington issued this flash flood warning at Sep 23, 2021, 2:34 AM EDT for Frederick County, Washington 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: Sep 23, 2021, 2:34 AM EDT (06:34 UTC)
Expired: Sep 23, 2021, 5:30 AM EDT
In force: 3 hr
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties Frederick County, MD, Washington County, MD

The radar

The Sterling radar (KLWX), 50 km from the middle of the area, began a volume at 06:38 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
Sep 23, 4:30 AM EDT	FLOOD	Brunswick, MD	ROAD CLOSURES DUE TO FLOODING STARTING TO BE REPORTED IN THE BRUNSWICK, JEFFERSON, AND KNOXVILLE AREAS

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, 6.6 hours before the alert went out and 54 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: 100 J/kg
Mixed-layer CIN: -17 J/kg
Mixed-layer LCL: 652 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 161 m²/s²
0-3 km storm-relative helicity: 199 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

180 
WGUS51 KLWX 230634
FFWLWX
MDC021-043-230930-
/O.NEW.KLWX.FF.W.0075.210923T0634Z-210923T0930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
234 AM EDT Thu Sep 23 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  Western Frederick County in north central Maryland...
  Eastern Washington County in north central Maryland...

* Until 530 AM EDT.

* At 234 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 1 to 2 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...
  Robinwood...                       Brunswick...
  Boonsboro...                       Smithsburg...
  Braddock Heights...                Mount Aetna...
  Mount Lena...                      San Mar...
  Wolfsville...                      Point Of Rocks...
  Jefferson...                       Myersville...
  Cavetown...                        Leitersburg...
  Fort Ritchie...                    Rosemont...
  Chewsville...                      Ringgold...
  Burkittsville...                   Pleasant Walk...

This includes the following Flood Prone Roads:
Stottlemeyer Road near Middle Creek...
Brethren Church Road near Catoctin Creek...
Shank Road near Catoctin Creek...
Station Road near Catoctin Creek...
Hollow Road near Hollow Road Creek...
Bennies Hill Road near Cone Branch...
Sigler Road near Catoctin Creek Tributary...
Brockton Court at Brockton Drive...


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 3972 7766 3972 7748 3958 7749 3939 7750
      3927 7753 3927 7755 3928 7755 3929 7756
      3930 7756 3931 7757 3930 7759 3931 7765

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

$$

ADS

2 follow-up statements

465 
WGUS71 KLWX 230832
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
432 AM EDT Thu Sep 23 2021

MDC021-043-230930-
/O.CON.KLWX.FF.W.0075.000000T0000Z-210923T0930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Frederick MD-Washington MD-
432 AM EDT Thu Sep 23 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 530 AM EDT EARLY THIS 
MORNING FOR WESTERN FREDERICK AND EASTERN WASHINGTON COUNTIES IN 
NORTH CENTRAL MARYLAND...

At 432 AM EDT, local law enforcement reported road closures due to 
flooding in the Brunswick, Knoxville, and Jefferson areas. Between 2 
and 3 inches of rain have fallen. Additional rainfall amounts up to 
0.5 inches are possible in the warned area. Flash flooding is 
already occurring.

HAZARD...Life threatening flash flooding. Heavy rain producing
         flash flooding.

SOURCE...Law enforcement reported.

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

Some locations that will experience flash flooding include...
Robinwood...                       Brunswick...
Boonsboro...                       Smithsburg...
Braddock Heights...                Mount Aetna...
Mount Lena...                      San Mar...
Wolfsville...                      Point Of Rocks...
Jefferson...                       Myersville...
Cavetown...                        Leitersburg...
Fort Ritchie...                    Rosemont...
Chewsville...                      Ringgold...
Burkittsville...                   Pleasant Walk...

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 3972 7766 3972 7748 3958 7749 3939 7750
      3927 7753 3927 7755 3928 7755 3929 7756
      3930 7756 3931 7757 3930 7759 3931 7765

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

ADS

316 
WGUS71 KLWX 230925
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
525 AM EDT Thu Sep 23 2021

MDC021-043-230935-
/O.EXP.KLWX.FF.W.0075.000000T0000Z-210923T0930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Frederick MD-Washington MD-
525 AM EDT Thu Sep 23 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 530 AM EDT EARLY THIS MORNING 
FOR WESTERN FREDERICK AND EASTERN WASHINGTON COUNTIES IN NORTH 
CENTRAL MARYLAND...

The heaviest rain has ended, so rapidly rising water is no longer a 
threat. However, moderate rain continues, and flooding is ongoing in 
Frederick County. A Flood Warning remains in effect.

A Flash Flood Watch remains in effect until 800 AM EDT for portions 
of north central Maryland, northern Virginia and panhandle West 
Virginia.

LAT...LON 3972 7766 3972 7748 3958 7749 3939 7750
      3927 7753 3927 7755 3928 7755 3929 7756
      3930 7756 3931 7757 3930 7759 3931 7765

$$

ADS

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 23, 12:25 AM EDT	Coastal Flood Advisory	LWX	Charles	8 hr
Sep 23, 2:02 AM EDT	Areal Flood Warning	LWX	Frederick, Washington	10 hr
Sep 23, 3:47 AM EDT	Areal Flood Warning	LWX	Montgomery	12 hr
Sep 23, 3:53 AM EDT	Areal Flood Warning	LWX	Carroll, Frederick	17 hr
Sep 23, 4:17 AM EDT	Flash Flood Warning Considerable damage threat	LWX	Frederick	3 hr
Sep 23, 4:41 AM EDT	Areal Flood Warning	LWX	Howard, Montgomery	9 hr
Sep 23, 5:35 AM EDT	Areal Flood Warning	LWX	Carroll, Frederick	6 hr
Sep 23, 7:08 AM EDT	River Flood Warning	LWX	Montgomery	16 hr
Sep 23, 7:56 AM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Harford	22 min
Sep 23, 8:04 AM EDT	Areal Flood Warning	LWX	Anne Arundel, Baltimore, Harford, Howard, Montgomery, Prince George's and 1 more	10 hr
Sep 23, 9:02 AM EDT	Areal Flood Warning	LWX	Cecil	9 hr
Sep 23, 9:27 AM EDT	Severe Thunderstorm Warning	LWX	Cecil, Harford	78 min
Sep 23, 12:11 PM EDT	Areal Flood Warning	LWX	Frederick	5 hr
Sep 23, 1:18 PM EDT	River Flood Warning	LWX	Frederick	25 hr
Sep 23, 2:15 PM EDT	Coastal Flood Advisory	LWX	Charles	6 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.