Alert archive / Virginia / Mesoscale Discussions in 2018

Mesoscale Discussion 1468

September 17, 201824 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Sep 17, 2018, 10:28 AM EDT for 24 counties in Virginia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Sep 17, 2018, 10:28 AM EDT (14:28 UTC)
Expired: Sep 17, 2018, 12:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 24 counties

Amelia County, VA, Brunswick County, VA, Buckingham County, VA, Charlotte County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Hopewell, VA, City of Petersburg, VA, City of Richmond, VA, Cumberland County, VA, Dinwiddie County, VA, Fluvanna County, VA, Goochland County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Louisa County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nottoway County, VA, Powhatan County, VA, Prince Edward County, VA

The radar

The Norfolk radar (KAKQ), 91 km from the middle of the area, began a volume at 14:31 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

Roanoke, VA (KRNK), launched 12:00Z, 2.5 hours before the alert went out and 131 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: 30 J/kg
Mixed-layer CIN: -6 J/kg
Mixed-layer LCL: 682 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 164 m²/s²
0-3 km storm-relative helicity: 192 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.2

Open this sounding in Storm Lab

The text

As transmitted.

<!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
Sep 17, 3:25 PM EDT	Mesoscale Discussion	SPC	Amelia, Brunswick, Caroline, Chesterfield, Dinwiddie, Essex and 16 more	2 hr
Sep 17, 3:42 PM EDT	Tornado Watch	SPC	Amelia, Arlington, Caroline, Chesterfield, Cumberland, Essex and 22 more	4 hr
Sep 17, 7:09 PM EDT	Mesoscale Discussion	SPC	Amelia, Arlington, Caroline, Charles City, Chesterfield, Culpeper and 31 more	2 hr

Nearby

Mesoscale Discussions in Virginia, 2018 Every mesoscale discussion in 2018

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.