Alert archive / Maryland / Flash Flood Warnings in 2021

Flash Flood Warning 66, NWS Baltimore/Washington

September 1, 2021Carroll County, Frederick County, Maryland

NWS Baltimore/Washington issued this flash flood warning at Sep 1, 2021, 3:25 PM EDT for Carroll County, Frederick County, Maryland. It was in force for 5 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 1, 2021, 3:25 PM EDT (19:25 UTC)
Expired: Sep 1, 2021, 8:16 PM EDT
In force: 5 hr
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties Carroll County, MD, Frederick County, MD

The radar

The Sterling radar (KLWX), 71 km from the middle of the area, began a volume at 19:29 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 1, 3:41 PM EDT	FLOOD	2 Nw Ballenger Creek, MD	A VEHICLE WAS STRANDED IN HIGH WATER ON JEFFERSON PIKE AT GREENFIELD DRIVE NEAR BUTTERFLY BRANCH.

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, 7.4 hours before the alert went out and 71 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: 558 J/kg
Mixed-layer CIN: -21 J/kg
Mixed-layer LCL: 575 m above ground
0-6 km bulk shear: 48 kt
0-1 km storm-relative helicity: 122 m²/s²
0-3 km storm-relative helicity: 223 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 2.6

Open this sounding in Storm Lab

The text

As transmitted.

218 
WGUS51 KLWX 011925
FFWLWX
MDC013-021-012230-
/O.NEW.KLWX.FF.W.0066.210901T1925Z-210901T2230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
325 PM EDT Wed Sep 1 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  Western Carroll County in north central Maryland...
  Southern Frederick County in north central Maryland...

* Until 630 PM EDT.

* At 325 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 4 inches of rain 
  have fallen. Additional rainfall amounts of 2 to 3 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...
  Frederick...                       Westminster...
  Harry Grove Stadium...             Ballenger Creek...
  Mount Airy...                      Taneytown...
  Brunswick...                       Braddock Heights...
  New Market...                      Linganore-Bartonsville...
  Green Valley...                    Adamstown...
  Jefferson...                       New Windsor...
  Buckeystown...                     Union Bridge...
  Libertytown...                     Monrovia...
  Unionville...                      Linwood...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3960 7720 3972 7716 3972 7707 3972 7706
      3972 7705 3972 7701 3972 7700 3972 7699
      3948 7705 3935 7719 3930 7737 3932 7761
      3942 7752 3940 7731

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

$$

BKF

2 follow-up statements

760 
WGUS51 KLWX 012209
FFWLWX
MDC013-021-020130-
/O.EXT.KLWX.FF.W.0066.000000T0000Z-210902T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
609 PM EDT Wed Sep 1 2021

The National Weather Service in Sterling Virginia has extended the

* Flash Flood Warning for...
  Western Carroll County in north central Maryland...
  Southern Frederick County in north central Maryland...

* Until 930 PM EDT.

* At 609 PM EDT, Between 3 and 5 inches of rain fell earlier. 
  Additional rainfall amounts of 0.5 to 1 inch are possible in the 
  warned area. Flash flooding is ongoing or expected to begin 
  shortly. Stream gauges at Big Pipe Creek in Bruceville and the 
  Monocacy River at Bridgeport are experiencing minor flooding with 
  water levels still rising. Flash flooding will continue to be a 
  threat this evening.

  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...
  Frederick...                       Westminster...
  Harry Grove Stadium...             Ballenger Creek...
  Mount Airy...                      Taneytown...
  Brunswick...                       Braddock Heights...
  New Market...                      Linganore-Bartonsville...
  Green Valley...                    Adamstown...
  Jefferson...                       New Windsor...
  Buckeystown...                     Union Bridge...
  Libertytown...                     Monrovia...
  Unionville...                      Linwood...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Stay away or be swept away. River banks and culverts can become 
unstable and unsafe.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3960 7720 3972 7716 3972 7707 3972 7706
      3972 7705 3972 7701 3972 7700 3972 7699
      3948 7705 3935 7719 3930 7737 3932 7761
      3942 7752 3940 7731

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL...0.5-1 INCH IN 1 HOUR

$$

LFR

578 
WGUS71 KLWX 020016
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
816 PM EDT Wed Sep 1 2021

MDC013-021-020026-
/O.CAN.KLWX.FF.W.0066.000000T0000Z-210902T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Carroll MD-Frederick MD-
816 PM EDT Wed Sep 1 2021

...FLASH FLOOD WARNING FOR WESTERN CARROLL AND SOUTHERN FREDERICK 
COUNTIES IN NORTH CENTRAL MARYLAND HAS BEEN REPLACED WITH A FLOOD 
WARNING...

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

LAT...LON 3960 7720 3972 7716 3972 7707 3972 7706
      3972 7705 3972 7701 3972 7700 3972 7699
      3948 7705 3935 7719 3930 7737 3932 7761
      3942 7752 3940 7731

$$

JMG

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 31, 9:06 PM EDT	Coastal Flood Watch	LWX	Anne Arundel	22 hr
Aug 31, 9:36 PM EDT	River Flood Warning	LWX	Washington	68 hr
Aug 31, 9:44 PM EDT	River Flood Watch	LWX	Frederick	25 hr
Aug 31, 9:44 PM EDT	River Flood Watch	LWX	Montgomery	48 hr
Aug 31, 9:44 PM EDT	River Flood Watch	LWX	Washington	25 hr
Aug 31, 9:44 PM EDT	River Flood Watch	LWX	Montgomery	25 hr
Sep 1, 3:23 AM EDT	Areal Flood Warning	LWX	Montgomery	8 hr
Sep 1, 3:24 AM EDT	Severe Thunderstorm Warning	LWX	Montgomery, Prince George's	51 min
Sep 1, 3:50 AM EDT	Areal Flood Warning	LWX	Montgomery, Prince George's	6 hr
Sep 1, 4:00 AM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel, Prince George's	60 min
Sep 1, 4:10 AM EDT	Areal Flood Warning	LWX	Anne Arundel, Baltimore, Howard, City of Baltimore	6 hr
Sep 1, 4:34 AM EDT	Areal Flood Warning	LWX	Montgomery	6 hr
Sep 1, 4:39 AM EDT	Areal Flood Warning	LWX	Anne Arundel, Baltimore, Howard, City of Baltimore	5 hr
Sep 1, 4:50 AM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel, Baltimore, City of Baltimore	40 min
Sep 1, 5:41 AM EDT	Areal Flood Warning	LWX	Cecil, Harford	5 hr
Sep 1, 6:15 AM EDT	Areal Flood Warning	LWX	Cecil	5 hr
Sep 1, 8:39 AM EDT	Flash Flood Warning	LWX	Allegany, Garrett	5 hr
Sep 1, 10:14 AM EDT	Coastal Flood Advisory	LWX	Anne Arundel, Baltimore, Calvert, Cecil, Harford, Saint Mary's and 1 more	19 hr
Sep 1, 12:52 PM EDT	Areal Flood Warning	LWX	Allegany	22 hr
Sep 1, 1:11 PM EDT	Tornado Warning	LWX	Charles, Prince George's	34 min
Sep 1, 1:23 PM EDT	Tornado Warning	LWX	Charles	17 min
Sep 1, 1:30 PM EDT	Areal Flood Warning	LWX	Carroll, Frederick, Washington	27 hr
Sep 1, 1:31 PM EDT	Tornado Warning	LWX	Charles, Saint Mary's	29 min
Sep 1, 1:46 PM EDT	Areal Flood Warning	LWX	Allegany, Garrett	16 hr
Sep 1, 1:56 PM EDT	Tornado Warning	LWX	Anne Arundel, Prince George's	34 min
Sep 1, 2:12 PM EDT	Tornado Warning	LWX	Baltimore	33 min
Sep 1, 2:23 PM EDT	Tornado Warning	LWX	Baltimore	15 min
Sep 1, 2:26 PM EDT	Flash Flood Warning Considerable damage threat	LWX	Carroll, Frederick	6 hr
Sep 1, 2:26 PM EDT	Tornado Warning	LWX	Baltimore, Harford	14 min
Sep 1, 2:27 PM EDT	Tornado Warning Tornado observed	LWX	Anne Arundel	15 min
Sep 1, 2:48 PM EDT	Tornado Warning Tornado observed	LWX	Baltimore, Harford	27 min
Sep 1, 3:10 PM EDT	Tornado Warning	LWX	Baltimore	16 min
Sep 1, 3:17 PM EDT	Tornado Warning	LWX	Harford	28 min
Sep 1, 3:34 PM EDT	Flash Flood Warning Considerable damage threat	LWX	Cecil, Harford	3 hr
Sep 1, 3:36 PM EDT	Wind Advisory	LWX	Allegany, Carroll, Frederick, Washington	7 hr
Sep 1, 3:49 PM EDT	Tornado Warning	LWX	Cecil, Harford	26 min
Sep 1, 4:13 PM EDT	River Flood Watch	LWX	Cecil	7 hr
Sep 1, 4:13 PM EDT	River Flood Warning	LWX	Allegany	7 hr
Sep 1, 4:14 PM EDT	River Flood Warning	LWX	Allegany	9 hr
Sep 1, 4:37 PM EDT	Areal Flood Warning	LWX	Baltimore, Carroll, Harford	13 hr
Sep 1, 5:46 PM EDT	Tornado Warning	LWX	Cecil	29 min
Sep 1, 6:08 PM EDT	Areal Flood Warning	LWX	Cecil, Harford	17 hr
Sep 1, 6:12 PM EDT	Tornado Warning	LWX	Cecil	19 min
Sep 1, 7:03 PM EDT	Coastal Flood Warning	LWX	Anne Arundel	8 hr
Sep 1, 7:27 PM EDT	Areal Flood Warning	LWX	Allegany, Washington	15 hr
Sep 1, 7:59 PM EDT	Areal Flood Warning	LWX	Carroll, Frederick	2 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.