Alert archive / Virginia / Mesoscale Discussions in 2018

Mesoscale Discussion 496

May 22, 2018Calvert County, Saint Mary's County, Maryland; 19 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at May 22, 2018, 7:24 PM EDT for Calvert County, Saint Mary's County, Maryland; 19 counties in Virginia. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: May 22, 2018, 7:24 PM EDT (23:24 UTC)
Expired: May 22, 2018, 9:00 PM EDT
In force: 96 min
Issued by: the Storm Prediction Center

All 21 counties

Calvert County, MD, Saint Mary's County, MD, Charles City County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Hopewell, VA, City of Richmond, VA, City of Williamsburg, VA, Essex County, VA, Gloucester County, VA, Henrico County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Lancaster County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northumberland County, VA, Richmond County, VA, Westmoreland County, VA

The radar

The Norfolk radar (KAKQ), 81 km from the middle of the area, began a volume at 23:26 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 11.4 hours before the alert went out and 133 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1338 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 23 m²/s²
0-3 km storm-relative helicity: 64 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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
May 22, 1:52 PM EDT	Mesoscale Discussion	SPC	Calvert, Charles, Prince George's, Saint Mary's	113 min
May 22, 2:33 PM EDT	Severe Thunderstorm Watch	SPC	Anne Arundel, Calvert, Charles, Howard, Montgomery, Prince George's and 1 more	6 hr
May 22, 4:50 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Calvert, Charles, Montgomery, Prince George's, Saint Mary's	115 min

Nearby

Mesoscale Discussions in Virginia, 2018 Mesoscale Discussions in Maryland, 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.