Alert archive / Virginia / Mesoscale Discussions in 2007

Mesoscale Discussion 1830

August 21, 200735 counties in North Carolina; 7 counties in Tennessee; 46 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Aug 21, 2007, 1:42 PM EDT for 35 counties in North Carolina; 7 counties in Tennessee; 46 counties in Virginia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 21, 2007, 1:42 PM EDT (17:42 UTC)
Expired: Aug 21, 2007, 3:45 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 88 counties

Alamance County, NC, Alexander County, NC, Alleghany County, NC, Ashe County, NC, Avery County, NC, Buncombe County, NC, Burke County, NC, Cabarrus County, NC, Caldwell County, NC, Caswell County, NC, Catawba County, NC, Cleveland County, NC, Davidson County, NC, Davie County, NC, Forsyth County, NC, Gaston County, NC, Guilford County, NC, Haywood County, NC, Henderson County, NC, Iredell County, NC, Lincoln County, NC, Madison County, NC, McDowell County, NC, Mitchell County, NC, Person County, NC, Randolph County, NC, Rockingham County, NC, Rowan County, NC, Rutherford County, NC, Stokes County, NC, Surry County, NC, Watauga County, NC, Wilkes County, NC, Yadkin County, NC, Yancey County, NC, Carter County, TN, Cocke County, TN, Greene County, TN, Johnson County, TN, Sullivan County, TN, Unicoi County, TN, Washington County, TN, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Bedford County, VA, Bland County, VA, Botetourt County, VA, Buckingham County, VA, Campbell County, VA, Carroll County, VA, Charlotte County, VA, City of Bristol, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Danville, VA, City of Galax, VA, City of Lexington, VA, City of Lynchburg, VA, City of Martinsville, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, City of Waynesboro, VA, Craig County, VA, Cumberland County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Grayson County, VA, Halifax County, VA, Henry County, VA, Lunenburg County, VA, Mecklenburg County, VA, Montgomery County, VA, Nelson County, VA, Nottoway County, VA, Patrick County, VA, Pittsylvania County, VA, Prince Edward County, VA, Pulaski County, VA, Roanoke County, VA, Rockbridge County, VA, Russell County, VA, Smyth County, VA, Washington County, VA, Wythe County, VA

The radar

The Roanoke radar (KFCX), 26 km from the middle of the area, began a volume at 17:45 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Roanoke, VA (KRNK), launched 12:00Z, 5.7 hours before the alert went out and 73 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: 69 J/kg
Mixed-layer CIN: -132 J/kg
Mixed-layer LCL: 1286 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 112 m²/s²
0-3 km storm-relative helicity: 122 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 21, 2:12 PM EDT	Severe Thunderstorm Watch	SPC	Alamance, Alexander, Alleghany, Ashe, Avery, Buncombe and 21 more	5 hr
Aug 21, 3:51 PM EDT	Mesoscale Discussion	SPC	Alamance, Alexander, Beaufort, Bertie, Cabarrus, Caldwell and 50 more	114 min
Aug 21, 4:23 PM EDT	Severe Thunderstorm Watch	SPC	Bertie, Camden, Chatham, Chowan, Currituck, Durham and 18 more	7 hr
Aug 21, 4:56 PM EDT	Mesoscale Discussion	SPC	Anson, Bladen, Cabarrus, Cleveland, Cumberland, Duplin and 16 more	3 hr
Aug 21, 6:10 PM EDT	Severe Thunderstorm Watch	SPC	Anson, Beaufort, Carteret, Craven, Cumberland, Dare and 18 more	6 hr
Aug 21, 6:12 PM EDT	Mesoscale Discussion	SPC	Alamance, Anson, Beaufort, Bertie, Bladen, Brunswick and 49 more	2 hr

Nearby

Mesoscale Discussions in Virginia, 2007 Mesoscale Discussions in North Carolina, 2007 Mesoscale Discussions in Tennessee, 2007 Every mesoscale discussion in 2007

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.