Synoptic Overview - An upper ridge of high pressure was centered over eastern Georgia, the forecast area (southwestern Virginia) on the northern periphery. An upper low was drifting slowly northward into east Texas. Southerly flow between the 2 systems was advecting tropical air into the forecast area. The PWAT (00 UTCWED roab: RNK 1.86, GSO 2.37) was near 200% of normal. A quasi-stationary boundary in the lower troposphere (showed up as a trof on the 00 UTC 925, 850, and 700 mb analysis) was the focus for deep convection over the northwest piedmont of North Carolina and south side Virginia. Thunderstorms were oriented west-east near the NC/VA border and kept regenerating along this boundary.

Severe Weather Reports - The flash flood resulted in two fatalities. Peak rainfall was around 10 inches in about 4 hours time.  Runoff from this rainfall resulted in flash flooding along Stuart and Matrimony creeks in the extreme southern part of Henry County, Virginia, and the extreme northern part of Rockingham County, North Carolina (F).  It is believed Stuart creek which is normally a few feet wide, covered an area half the width of a football field and rose to a depth that was 6 feet above Meeks Road.  This is where the two fatalities occurred.  

Stuart Creek looking downstream:

The car in the picture is approximately where the other car was when it was swept off the road.

300 MB Upper Air Analysis at 00 UTC on Wednesday, June 16, 2004 (8 PM EDT, Tuesday, June 15)
Streamlines clearly define position of the upper ridge and upper low over the southeast CONUS.  The flash flood location was at the apex of the upper ridge.

500 MB Upper Air Analysis at 00 UTC on Wednesday, June 16, 2004 (8 PM EDT, Tuesday, June 15).
Note wind diffluence between the RNK and GSO raobs. (Data over the pacific northwest is corrupted.)
 

700 MB Heights (solid black lines) and Equivalent Potential Temperature (dashed yellow lines) from the 00 UTC Upper Air Analysis Wednesday, June 16, 2004 (8 PM EDT, Tuesday, June 15).
The 700 mb trof was oriented west-east along the NC/VA border (blue dashed line). Note ridging to the north of the trof which likely resulted in the trof remaining quasistationary. The boundary was also evindent at both 850 and 925 mb.

850 MB Heights (solid black lines) and Equivalent Potential Temperature (yellow dashed lines), from the 00 UTC Upper Air Analysis on Wednesday, June 16, 2004 (8 PM EDT, Tuesday, June 15).

925 MB Heights (solid black lines) and Equivalent Potential Temperature (yellow dashed lines), from the 00 UTC Upper Air Analysis on Wednesday, June 16, 2004 (8 PM EDT, Tuesday, June 15).

Surface Analysis

Surface Analysis at 06Z on Wednesday, June 16, 2004 (2 AM EDT).

 

Moisture Transport

06 UTC ETA Forecast Moisture Transport and Advection at 850 MB for Wednesday, June 16, 2004.
In spite of the heavy rainfall, moisture continued to be replentished over the area allowing for the heavy rain to continue for several hours.

07 UTC Surface Theta E Analysis for Wednesday, June 16, 2004.
The persistent transport of moisture results in pool of high Theta-E air along the Virginia - North Carolina border.

Analyzed rawinsonde data for Greensboro, NC  (GSO) and Blacksburg, VA (RNK) for 00Z Wednesday, June 16, 2004 (8 PM EDT, Tuesday, June 15).
The PWAT in the GSO and RNK soundings were 2.38 and 1.87, respectively.  This was 200 percent of normal. 

 

 

Integrated Precipitable Water Vapor (IPW) from the Blacksburg ground-based GPS station.  Plot is from June 14 through
June 18 2004.   For comparison, the annual normals are in the figure that follows.
The RNK GPS station reported a maximum IPW of 5.0 centimeters between 00 and 02 UTC on June 16th.  This is equivalent to a PWAT of 1.97 inches.

 

Satellite

IR Imagery from 0015Z to 0845Z, Wednesday, June 16, 2004.
Click thumbnail to start loop.
(File size: 3.7MB)

 

Water Vapor Imagery from 0015Z to 0845Z, Wednesday, June 16, 2004.
(File size: 2.0MB)

Radar Imagery

Radar Loops from 0000Z to 0830Z, Wednesday, June 16, 2004.
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(File size: 3MB).

Radar Cross Section During the height of the Storm. Note the higher reflectivity cores were concentrated in an environment that was warmer than 0 degrees Celcius.