Alert archive / Virginia / Flash Flood Warnings in 2021

Flash Flood Warning 32, NWS Blacksburg, VA

August 19, 2021City of Roanoke, Virginia

NWS Blacksburg, VA issued this flash flood warning at Aug 19, 2021, 8:38 PM EDT for City of Roanoke, Virginia. It was in force for 112 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: Aug 19, 2021, 8:38 PM EDT (00:38 UTC)
Expired: Aug 19, 2021, 10:30 PM EDT
In force: 112 min
Issued by: NWS Blacksburg, VA
Area: Storm-based polygon
Flood severity: None

County City of Roanoke, VA

The radar

The Roanoke radar (KFCX), 40 km from the middle of the area, began a volume at 00:40 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 19, 9:00 PM EDT	HEAVY RAIN 2.32	2 Nw Vinton, VA	A PERSONAL WEATHER STATION RECORDED 2.32 INCHES OF RAINFALL FROM A THUNDERSTORM DURING A 90-MINUTE PERIOD. RAINFALL RATES WERE OBSERVED AT 2.1 INCHES PER HOUR DURING THIS STORM.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Roanoke, VA (KRNK), launched 00:00Z, 0.6 hours before the alert went out and 42 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: 231 J/kg
Mixed-layer CIN: -9 J/kg
Mixed-layer LCL: 703 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 33 m²/s²
0-3 km storm-relative helicity: 40 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

As transmitted.

000 
WGUS51 KRNK 200038
FFWRNK
VAC770-200230-
/O.NEW.KRNK.FF.W.0032.210820T0038Z-210820T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Blacksburg VA
838 PM EDT Thu Aug 19 2021

The National Weather Service in Blacksburg has issued a

* Flash Flood Warning for...
  The City of Roanoke in west central Virginia...

* Until 1030 PM EDT.

* At 838 PM EDT, emergency management reported thunderstorms 
  producing heavy rain across the warned area. Tinker Creek was 
  reported to be rising quickly by the emergency manager. Multiple 
  roads are also closed within the city. Between 1 and 2.5 inches of 
  rain have fallen. Flash flooding is already occurring.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Emergency management reported.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Roanoke...                         Salem...
  Vinton...                          Hollins...
  Cave Spring...

This includes the following streams and drainages...
  Gum Spring Branch, Roanoke River, Mason Creek, Murray Run, Carvin 
  Creek and Back Creek.

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.

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

&&

LAT...LON 3727 8001 3729 8002 3731 8002 3734 7997
      3732 7995 3733 7995 3732 7993 3733 7992
      3732 7992 3729 7988 3728 7988 3728 7991
      3726 7990 3724 7990 3721 7995 3724 7998
      3725 8000 3724 8003 3725 8004

FLASH FLOOD...OBSERVED

$$

BMG

2 follow-up statements

745 
WGUS71 KRNK 200115
FFSRNK

Flash Flood Statement
National Weather Service Blacksburg VA
915 PM EDT Thu Aug 19 2021

VAC770-200230-
/O.CON.KRNK.FF.W.0032.000000T0000Z-210820T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
City of Roanoke VA-
915 PM EDT Thu Aug 19 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1030 PM EDT THIS 
EVENING FOR THE CITY OF ROANOKE...

At 915 PM EDT, emergency management reported thunderstorms producing 
heavy rain across the warned area. Multiple road closures continue 
within the city. Between 1.5 and 2.5 inches of rain have fallen. 
Flash flooding is already occurring.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Emergency management reported.

IMPACT...Flash flooding of small creeks and streams, urban areas,
         highways, streets and underpasses as well as other poor
         drainage and low-lying areas.

Some locations that will experience flash flooding include...
  Roanoke...                         Salem...
Vinton...                          Hollins...
Cave Spring...

This includes the following streams and drainages...
  Gum Spring Branch, Tinker Creek, Mason Creek, Murray Run, Carvin 
  Creek and Back Creek.

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.

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

&&

LAT...LON 3727 8001 3729 8002 3731 8002 3734 7997
      3732 7995 3733 7995 3732 7993 3733 7992
      3732 7992 3729 7988 3728 7988 3728 7991
      3726 7990 3724 7990 3721 7995 3724 7998
      3725 8000 3724 8003 3725 8004

FLASH FLOOD...OBSERVED

$$

BMG

456 
WGUS71 KRNK 200225
FFSRNK

Flash Flood Statement
National Weather Service Blacksburg VA
1025 PM EDT Thu Aug 19 2021

VAC770-200235-
/O.EXP.KRNK.FF.W.0032.000000T0000Z-210820T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
City of Roanoke VA-
1025 PM EDT Thu Aug 19 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 1030 PM EDT THIS EVENING FOR 
THE CITY OF ROANOKE...

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.

LAT...LON 3727 8001 3729 8002 3731 8002 3734 7997
      3732 7995 3733 7995 3732 7993 3733 7992
      3732 7992 3729 7988 3728 7988 3728 7991
      3726 7990 3724 7990 3721 7995 3724 7998
      3725 8000 3724 8003 3725 8004

$$

AS

The office that day

Everything else NWS Blacksburg, VA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 20, 1:43 PM EDT	Special Weather Statement	RNK	Botetourt, Rockbridge, City of Buena Vista, City of Lexington	47 min
Aug 20, 1:48 PM EDT	Special Weather Statement	RNK	Bath	27 min
Aug 20, 2:29 PM EDT	Special Weather Statement	RNK	Botetourt	31 min
Aug 20, 2:35 PM EDT	Special Weather Statement	RNK	Alleghany	25 min
Aug 20, 2:51 PM EDT	Special Weather Statement	RNK	Bedford	39 min
Aug 20, 3:01 PM EDT	Special Weather Statement	RNK	Alleghany	44 min
Aug 20, 3:43 PM EDT	Special Weather Statement	RNK	Roanoke	32 min
Aug 20, 5:39 PM EDT	Special Weather Statement	RNK	Halifax	21 min
Aug 20, 6:20 PM EDT	Special Weather Statement	RNK	Patrick	25 min

Nearby

Flash Flood Warnings in Virginia, 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.