Alert archive / Maryland / Flash Flood Warnings in 2021

Flash Flood Warning 68, NWS Baltimore/Washington

September 8, 2021Frederick County, Maryland

NWS Baltimore/Washington issued this flash flood warning at Sep 8, 2021, 11:02 PM EDT for Frederick County, Maryland. It was in force for 78 min. 2 reports 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 8, 2021, 11:02 PM EDT (03:02 UTC)
Expired: Sep 9, 2021, 12:20 AM EDT
In force: 78 min
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Frederick County, MD

The radar

The Sterling radar (KLWX), 49 km from the middle of the area, began a volume at 03:04 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 8, 11:03 PM EDT	FLASH FLOOD	1 Ssw Frederick, MD	SEVERAL ROADS BLOCKED BY RISING WATER. CARROLL PARKWAY COVERED BY 4 FEET OF WATER.
Sep 9, 12:00 AM EDT	FLOOD	Frederick, MD	WEST PATRICK RD CLOSED AT NORTH BENTZ ST DUE TO HIGH WATER

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, 3.0 hours before the alert went out and 52 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: 1652 J/kg
Mixed-layer CIN: -18 J/kg
Mixed-layer LCL: 1146 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 115 m²/s²
0-3 km storm-relative helicity: 136 m²/s²
Significant tornado parameter: 1.0
Supercell composite: 7.0

Open this sounding in Storm Lab

The text

As transmitted.

881 
WGUS51 KLWX 090302
FFWLWX
MDC021-090615-
/O.NEW.KLWX.FF.W.0068.210909T0302Z-210909T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
1102 PM EDT Wed Sep 8 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  South Central Frederick County in north central Maryland...

* Until 215 AM EDT.

* At 1102 PM EDT, emergency management reported thunderstorms 
  producing heavy rain across the warned area. Between 1 and 3 
  inches of rain have fallen. Flash flooding is already occurring. 
  Carroll Parkway and West Patrick Street were closed due to several 
  feet of water in the roadway.

  HAZARD...Life threatening flash flooding. Thunderstorms
           producing flash flooding.

  SOURCE...Emergency management reported.

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

* Some locations that will experience flash flooding include...
  Frederick...                       Harry Grove Stadium...
  Ballenger Creek...                 Walkersville...
  Braddock Heights...                Linganore-Bartonsville...
  Discovery-Spring Garden...         Clover Hill...
  Adamstown...                       Buckeystown...
  Bloomfield...                      Ijamsville...
  Mount Pleasant...                  Clifton...
  Park Mills...

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 3946 7748 3948 7744 3951 7740 3948 7727
      3938 7729 3931 7736 3929 7744 3936 7750

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

$$

DHOF

2 follow-up statements

266 
WGUS71 KLWX 090312
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
1112 PM EDT Wed Sep 8 2021

MDC021-090615-
/O.CON.KLWX.FF.W.0068.000000T0000Z-210909T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Frederick MD-
1112 PM EDT Wed Sep 8 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 215 AM EDT THURSDAY 
FOR SOUTH CENTRAL FREDERICK COUNTY IN NORTH CENTRAL MARYLAND...

At 1112 PM EDT, emergency management reported thunderstorms 
producing heavy rain across the warned area. Between 1 and 3 inches 
of rain have fallen. Flash flooding is already occurring.

HAZARD...Life threatening flash flooding. Thunderstorms producing
         flash flooding.

SOURCE...Emergency management reported.

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

Some locations that will experience flash flooding include...
  Frederick...                       Harry Grove Stadium...
Ballenger Creek...                 Walkersville...
Braddock Heights...                Linganore-Bartonsville...
Discovery-Spring Garden...         Clover Hill...
Adamstown...                       Buckeystown...
Bloomfield...                      Ijamsville...
Mount Pleasant...                  Clifton...
Park Mills...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Basement flooding can occur quickly and create a life-threatening 
situation. If you are in a basement, or a residence below street 
level, move to a higher floor immediately.

Be especially cautious at night when it is harder to recognize the 
dangers of flooding. Turn around, don't drown when encountering 
flooded roadways.

&&

LAT...LON 3946 7748 3948 7744 3951 7740 3948 7727
      3938 7729 3931 7736 3929 7744 3936 7750

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

$$

DHOF

419 
WGUS71 KLWX 090420
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
1220 AM EDT Thu Sep 9 2021

MDC021-090430-
/O.CAN.KLWX.FF.W.0068.000000T0000Z-210909T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Frederick MD-
1220 AM EDT Thu Sep 9 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTH CENTRAL FREDERICK 
COUNTY IN NORTH CENTRAL MARYLAND...

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

A Flash Flood Watch remains in effect until 200 AM EDT for portions 
of central Maryland, north central Maryland, northeast Maryland and 
northern Maryland.

LAT...LON 3946 7748 3948 7744 3951 7740 3948 7727
      3938 7729 3931 7736 3929 7744 3936 7750

$$

LFR

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 8, 9:11 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Washington	64 min
Sep 8, 9:21 PM EDT	Severe Thunderstorm Warning	LWX	Carroll, Frederick	54 min
Sep 8, 10:18 PM EDT	Areal Flood Warning	LWX	Carroll, Frederick	3 hr
Sep 8, 11:05 PM EDT	Areal Flood Warning	LWX	Carroll, Frederick	5 hr
Sep 8, 11:57 PM EDT	Areal Flood Warning	LWX	Carroll, Frederick, Howard	4 hr
Sep 9, 12:17 AM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Cecil, Harford	43 min
Sep 9, 3:29 AM EDT	Coastal Flood Advisory	LWX	Anne Arundel	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.