Alert archive / Maryland / Flash Flood Warnings in 2021

Flash Flood Warning 70, NWS Baltimore/Washington

September 15, 2021Frederick County, Washington County, Maryland

NWS Baltimore/Washington issued this flash flood warning at Sep 15, 2021, 7:22 PM EDT for Frederick County, Washington County, Maryland. It was in force for 64 min. 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 15, 2021, 7:22 PM EDT (23:22 UTC)
Expired: Sep 15, 2021, 8:26 PM EDT
In force: 64 min
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), 79 km from the middle of the area, began a volume at 23:25 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 15, 7:35 PM EDT	FLOOD	3 E Smithsburg, MD	EDGEMONT CREEK FLOWING ACROSS PLEASANT VALLEY ROAD.

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, 11.4 hours before the alert went out and 82 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: 13 J/kg
Mixed-layer CIN: -270 J/kg
Mixed-layer LCL: 1457 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 73 m²/s²
0-3 km storm-relative helicity: 106 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

459 
WGUS51 KLWX 152322
FFWLWX
MDC021-043-160230-
/O.NEW.KLWX.FF.W.0070.210915T2322Z-210916T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Baltimore MD/Washington DC
722 PM EDT Wed Sep 15 2021

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Warning for...
  North Central Frederick County in north central Maryland...
  Northeastern Washington County in north central Maryland...

* Until 1030 PM EDT.

* At 722 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 3 inches of rain 
  have fallen. The expected rainfall rate is 1 to 2 inches in 1 
  hour. 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...
  Smithsburg...                      Cavetown...
  Sabillasville...                   Fort Ritchie...
  Cascade...                         Highfield...

This includes the following streams and drainages...
  Owens Creek, Friends Creek, Antietam Creek, Little Antietam Creek, 
  Grove Creek and Beaver Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3965 7759 3965 7762 3967 7756 3969 7752
      3972 7748 3972 7747 3972 7745 3972 7741
      3966 7750

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

$$

RCM

1 follow-up statement

443 
WGUS71 KLWX 160026
FFSLWX

Flash Flood Statement
National Weather Service Baltimore MD/Washington DC
826 PM EDT Wed Sep 15 2021

MDC021-043-160036-
/O.CAN.KLWX.FF.W.0070.000000T0000Z-210916T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Frederick MD-Washington MD-
826 PM EDT Wed Sep 15 2021

...FLASH FLOOD WARNING IS CHANGED TO A FLOOD WARNING FOR NORTH 
CENTRAL FREDERICK AND NORTHEASTERN WASHINGTON COUNTIES IN NORTH 
CENTRAL MARYLAND...

The heavy rain has ended. Flash flooding is no longer expected to 
pose a threat. A flood warning has replaced this flash flood 
warning. Please continue to heed remaining road closures.

LAT...LON 3965 7759 3965 7762 3967 7756 3969 7752
      3972 7748 3972 7747 3972 7745 3972 7741
      3966 7750

$$

RCM

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 15, 2:54 PM EDT	Coastal Flood Advisory	LWX	Anne Arundel, Baltimore, Harford, City of Baltimore	13 hr
Sep 15, 3:45 PM EDT	Severe Thunderstorm Warning	LWX	Allegany	16 min
Sep 15, 5:15 PM EDT	Severe Thunderstorm Warning	LWX	Washington	30 min
Sep 15, 5:42 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Washington	48 min
Sep 15, 5:52 PM EDT	Areal Flood Warning	LWX	Washington	115 min
Sep 15, 5:52 PM EDT	Severe Thunderstorm Warning	LWX	Washington	38 min
Sep 15, 6:20 PM EDT	Flash Flood Warning Considerable damage threat	LWX	Washington	2 hr
Sep 15, 6:23 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Washington	52 min
Sep 15, 6:28 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Washington	34 min
Sep 15, 6:35 PM EDT	Areal Flood Warning	LWX	Frederick, Washington	113 min

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.