Alert archive / Maryland / Flash Flood Warnings in 2020

Flash Flood Warning 33, NWS Philadelphia/Mount Holly

August 4, 20204 counties in Maryland

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 4, 2020, 7:50 AM EDT for 4 counties in Maryland. It was in force for 4 hr. 13 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: Aug 4, 2020, 7:50 AM EDT (11:50 UTC)
Expired: Aug 4, 2020, 11:45 AM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Caroline County, MD, Kent County, MD, Queen Anne's County, MD, Talbot County, MD

The radar

The Dover AFB radar (KDOX), 69 km from the middle of the area, began a volume at 11:48 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
Aug 4, 8:00 AM EDT	HEAVY RAIN 3.86	2 Ese Grasonville, MD	COCORAHS STATION MD-QA-6 QUEENSTOWN 2.6 S.
Aug 4, 8:00 AM EDT	HEAVY RAIN 3.9	1 Se Saint Michaels, MD	COCORAHS STATION MD-TB-4 ST. MICHAELS 0.7 SE.
Aug 4, 8:30 AM EDT	FLOOD	Chester, MD	STREET FLOODING IN CHESTER, MD.
Aug 4, 8:30 AM EDT	FLOOD	Chester, MD	STREET FLOODING IN CHESTER, MD.
Aug 4, 8:30 AM EDT	HEAVY RAIN 5.5	2 N Easton, MD	COCORAHS STATION MD-TB-20 EASTON 2.3 NNW.
Aug 4, 8:55 AM EDT	HEAVY RAIN 8.1	Trappe, MD	RAIN SINCE MIDNIGHT. STILL RAINING.
Aug 4, 9:00 AM EDT	FLASH FLOOD	3 Ssw Skipton, MD	FLOODING ON STATE HIGHWAY 662 BETWEEN SHARP ROAD AND PLEASANT VALLEY DRIVE. TIME BASED ON DISPATCH REPORTS AND SOCIAL MEDIA POSTS.
Aug 4, 9:37 AM EDT	FLASH FLOOD	1 S Trappe, MD	U.S. HIGHWAY 50 WESTBOUND CLOSED AT BARBER ROAD FROM FLASH FLOODING. TIME BASED ON DISPATCH REPORT.
Aug 4, 9:45 AM EDT	HEAVY RAIN 4.04	4 Nnw Copperville, MD	MESONET STATION 8943D 4 NNW COPPERVILLE.
Aug 4, 10:20 AM EDT	HEAVY RAIN 2.12	3 E Oxford, MD	MESONET STATION EW5058 OXFORD.
Aug 4, 10:43 AM EDT	FLASH FLOOD	1 Ne Chester, MD	FLOODING ON STATE HIGHWAY 18 BETWEEN PINEY CREEK ROAD AND MAIN STREET FORCED ROAD CLOSURES. TIME BASED ON DISPATCH REPORT.
Aug 4, 10:43 AM EDT	FLASH FLOOD	1 Ne Chester, MD	FLOODING ON STATE HIGHWAY 18 BETWEEN PINEY CREEK ROAD AND MAIN STREET FORCED ROAD CLOSURES. TIME BASED ON DISPATCH REPORT.
Aug 4, 10:45 AM EDT	HEAVY RAIN 7.24	3 S Grasonville, MD	MESONET STATION EW5728 GRASONVILLE.

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, 11.8 hours before the alert went out and 101 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: 89 J/kg
Mixed-layer CIN: -54 J/kg
Mixed-layer LCL: 889 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 65 m²/s²
0-3 km storm-relative helicity: 140 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

049 
WGUS51 KPHI 041150
FFWPHI
MDC011-029-035-041-041545-
/O.NEW.KPHI.FF.W.0033.200804T1150Z-200804T1545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
750 AM EDT Tue Aug 4 2020

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Talbot County in eastern Maryland...
  Southwestern Queen Anne's County in northeastern Maryland...
  Southwestern Caroline County in eastern Maryland...
  Southwestern Kent County in northeastern Maryland...

* Until 1145 AM EDT.

* At 747 AM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Up to two inches of rain have 
  fallen over the last hour. This is on top of the heavy rain that 
  fell overnight. In addition, higher tides will affect runoff. As a 
  result, flash flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar indicated.

  IMPACT...Flooding of small creeks and streams, urban areas, 
           highways, streets and underpasses as well as other 
           drainage and low lying areas.

* Some locations that could experience flooding include...
  Easton, Centerville, Talbot, Centreville, Trappe, St. Michaels,
  Tanyard, Grasonville, Starr, Stevensville, Skipton, Copperville,
  Chester, Matthews, Choptank, Wye Mills, Hambleton, Windyhill,
  Cordova and Carville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Protecting yourself from immediate threats to life and safety shall
take priority.  Whenever possible, as long as it does not cause
greater harm, all COVID-19 protective action guidance should be
followed.

A Flash Flood Warning means that flooding is imminent or occurring.
If you are in the warned area move to higher ground immediately.
Residents living along streams and creeks should take immediate
precautions to protect life and property.

&&

LAT...LON 3904 7631 3897 7622 3900 7617 3905 7621
      3905 7598 3868 7592 3857 7603 3876 7622
      3868 7634 3884 7627 3879 7619 3894 7621
      3897 7625 3890 7628 3894 7627 3891 7629
      3896 7631 3891 7634 3885 7636 3886 7637

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-3 INCHES IN 1 HOUR

$$

Kruzdlo

1 follow-up statement

644 
WGUS71 KPHI 041538
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1138 AM EDT Tue Aug 4 2020

MDC011-029-035-041-041545-
/O.EXP.KPHI.FF.W.0033.000000T0000Z-200804T1545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Talbot MD-Queen Anne's MD-Caroline MD-Kent MD-
1138 AM EDT Tue Aug 4 2020

...THE FLASH FLOOD WARNING FOR TALBOT...SOUTHWESTERN QUEEN ANNE'S...
SOUTHWESTERN CAROLINE AND SOUTHWESTERN KENT COUNTIES WILL EXPIRE AT
1145 AM EDT...

The heavy rain has ended. Water is receding. Please continue to heed 
any remaining road closures.

LAT...LON 3904 7631 3897 7622 3900 7617 3905 7621
      3905 7598 3868 7592 3857 7603 3876 7622
      3868 7634 3884 7627 3879 7619 3894 7621
      3897 7625 3890 7628 3894 7627 3891 7629
      3896 7631 3891 7634 3885 7636 3886 7637

$$

Kruzdlo

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 4, 1:33 AM EDT	Areal Flood Advisory	PHI	Caroline, Kent, Queen Anne's, Talbot	4 hr
Aug 4, 2:10 AM EDT	Flash Flood Warning	PHI	Caroline, Kent, Queen Anne's, Talbot	4 hr
Aug 4, 5:17 AM EDT	Areal Flood Advisory	PHI	Cecil, Kent	4 hr
Aug 4, 6:55 AM EDT	Tornado Warning	PHI	Kent, Queen Anne's	35 min
Aug 4, 7:22 AM EDT	Tornado Warning	PHI	Kent, Queen Anne's	23 min
Aug 4, 8:13 AM EDT	Tornado Warning	PHI	Kent, Queen Anne's, Talbot	26 min
Aug 4, 8:27 AM EDT	Tornado Warning	PHI	Caroline, Cecil, Kent, Queen Anne's	33 min
Aug 4, 8:50 AM EDT	Flash Flood Warning	PHI	Caroline, Cecil, Kent, Queen Anne's	4 hr
Aug 4, 8:56 AM EDT	Tornado Warning	PHI	Cecil	34 min
Aug 4, 9:23 AM EDT	Flash Flood Warning	PHI	Cecil	4 hr
Aug 4, 9:23 AM EDT	Tornado Warning Tornado observed	PHI	Cecil	22 min
Aug 4, 1:59 PM EDT	Areal Flood Warning	PHI	Cecil	9 hr

Nearby

Flash Flood Warnings in Maryland, 2020 Every flash flood warning in 2020

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.