Alert archive / Virginia / Flash Flood Watches in 2011

Flash Flood Watch 12, NWS Blacksburg, VA

September 23, 20118 counties in Virginia; Caswell County, Rockingham County, North Carolina

NWS Blacksburg, VA issued this flash flood watch at Sep 23, 2011, 9:36 AM EDT for 8 counties in Virginia; Caswell County, Rockingham County, North Carolina. It took effect at Sep 23, 2011, 10:00 AM EDT. It was in force for 5 hr.

The area

The counties it named.

The facts

Issued
Sep 23, 2011, 9:36 AM EDT (13:36 UTC)
In effect from
Sep 23, 2011, 10:00 AM EDT
Expired
Sep 23, 2011, 2:42 PM EDT
In force
5 hr
Issued by
NWS Blacksburg, VA
Flood severity
None

Counties Caswell County, NC, Rockingham County, NC, Appomattox County, VA, Buckingham County, VA, Campbell County, VA, Charlotte County, VA, City of Danville, VA, City of Lynchburg, VA, Halifax County, VA, Pittsylvania County, VA

The radar

The Roanoke radar (KFCX), 104 km from the middle of the area, began a volume at 13:36 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.

The nearest sounding before it

Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 1.6 hours before the alert went out and 120 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-pSkew-T log-p diagram, Greensboro/Hi Pt, NC at 12:00Z on 2011-09-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 120 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Greensboro/Hi Pt, NC at 12:00Z on 2011-09-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 41 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
120 J/kg
Mixed-layer CIN
-12 J/kg
Mixed-layer LCL
494 m above ground
0-6 km bulk shear
29 kt
0-1 km storm-relative helicity
41 m²/s²
0-3 km storm-relative helicity
86 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0

Open this sounding in Storm Lab

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 23, 5:18 AM EDTSpecial Weather StatementRNKCharlotte, Halifax, City of Danville57 min
Sep 23, 8:27 AM EDTSpecial Weather StatementRNKCharlotte, Halifax63 min

Nearby

Flash Flood Watches in Virginia, 2011Flash Flood Watches in North Carolina, 2011Every flash flood watch in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.