Alert archive / Virginia / Mesoscale Discussions in 2004

Mesoscale Discussion 2060

August 20, 20044 states

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2004, 4:03 PM EDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Aug 20, 2004, 4:03 PM EDT (20:03 UTC)
Expired
Aug 20, 2004, 6:30 PM EDT
In force
2 hr
Issued by
the Storm Prediction Center
All 80 counties

Allegany County, MD, Baltimore County, MD, Carroll County, MD, City of Baltimore, MD, Frederick County, MD, Garrett County, MD, Howard County, MD, Montgomery County, MD, Washington County, MD, Adams County, PA, Bedford County, PA, Berks County, PA, Cumberland County, PA, Franklin County, PA, Fulton County, PA, Lancaster County, PA, Lebanon County, PA, Somerset County, PA, York County, PA, Albemarle County, VA, Arlington County, VA, Augusta County, VA, Bath County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Harrisonburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, Highland County, VA, Loudoun County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Stafford County, VA, Warren County, VA, Barbour County, WV, Berkeley County, WV, Braxton County, WV, Calhoun County, WV, Clay County, WV, Doddridge County, WV, Gilmer County, WV, Grant County, WV, Greenbrier County, WV, Hampshire County, WV, Hardy County, WV, Harrison County, WV, Jefferson County, WV, Lewis County, WV, Marion County, WV, Mineral County, WV, Monongalia County, WV, Morgan County, WV, Nicholas County, WV, Pendleton County, WV, Pocahontas County, WV, Preston County, WV, Randolph County, WV, Ritchie County, WV, Taylor County, WV, Tucker County, WV, Upshur County, WV, Webster County, WV

The radar

The Sterling radar (KLWX), 117 km from the middle of the area, began a volume at 20:06 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.1 hours before the alert went out and 125 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, Washington/Dulle, VA at 12:00Z on 2004-08-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 410 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 12:00Z on 2004-08-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 2 square meters per square second.193958Sfc1 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
410 J/kg
Mixed-layer CIN
-118 J/kg
Mixed-layer LCL
1428 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
2 m²/s²
0-3 km storm-relative helicity
24 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.2

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.

IssuedProductOfficeCountiesLasted
Aug 19, 8:28 PM EDTMesoscale DiscussionSPCAnne Arundel, Baltimore, Carroll, Cecil, Frederick, Harford and 5 more92 min
Aug 20, 4:25 PM EDTSevere Thunderstorm WatchSPCGarrett5 hr
Aug 20, 7:15 PM EDTMesoscale DiscussionSPCAllegany, Garrett90 min
Aug 20, 11:56 AM EDTMesoscale DiscussionSPCBradford, Centre, Clinton, Columbia, Lackawanna, Luzerne and 10 more2 hr
Aug 20, 2:05 PM EDTSevere Thunderstorm WatchSPCBlair, Bradford, Cambria, Cameron, Carbon, Centre and 27 more5 hr
Aug 20, 3:41 PM EDTMesoscale DiscussionSPCBlair, Bradford, Cambria, Cameron, Carbon, Centre and 27 more2 hr
Aug 20, 6:10 PM EDTSevere Thunderstorm WatchSPCBradford, Cameron, Carbon, Centre, Clinton, Columbia and 21 more5 hr

Nearby

Mesoscale Discussions in Virginia, 2004Mesoscale Discussions in West Virginia, 2004Mesoscale Discussions in Pennsylvania, 2004Every mesoscale discussion in 2004

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.