Alert archive / Washington / Mesoscale Discussions in 2017

Mesoscale Discussion 648

May 4, 201714 counties in Oregon; 15 counties in Washington

The Storm Prediction Center issued this mesoscale discussion at May 4, 2017, 3:34 PM PDT for 14 counties in Oregon; 15 counties in Washington. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued
May 4, 2017, 3:34 PM PDT (22:34 UTC)
Expired
May 4, 2017, 5:00 PM PDT
In force
86 min
Issued by
the Storm Prediction Center
Chance of a watch
60%
All 29 counties

Clackamas County, OR, Columbia County, OR, Douglas County, OR, Gilliam County, OR, Hood River County, OR, Jefferson County, OR, Lane County, OR, Linn County, OR, Marion County, OR, Morrow County, OR, Multnomah County, OR, Sherman County, OR, Wasco County, OR, Washington County, OR, Benton County, WA, Chelan County, WA, Clark County, WA, Cowlitz County, WA, Douglas County, WA, Franklin County, WA, Grant County, WA, King County, WA, Kittitas County, WA, Klickitat County, WA, Lewis County, WA, Pierce County, WA, Skamania County, WA, Thurston County, WA, Yakima County, WA

The watches that followed

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

The nearest sounding before it

Salem/Mcnary, OR (KSLE), launched 12:00Z, 10.6 hours before the alert went out and 138 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, Salem/Mcnary, OR at 12:00Z on 2017-05-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 6 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, Salem/Mcnary, OR at 12:00Z on 2017-05-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 12 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
6 J/kg
Mixed-layer CIN
-555 J/kg
Mixed-layer LCL
1172 m above ground
0-6 km bulk shear
20 kt
0-1 km storm-relative helicity
12 m²/s²
0-3 km storm-relative helicity
79 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.

IssuedProductOfficeCountiesLasted
May 4, 4:05 PM PDTSevere Thunderstorm WatchSPCClackamas, Douglas, Hood River, Lane, Linn, Marion and 1 more7 hr

Nearby

Mesoscale Discussions in Washington, 2017Mesoscale Discussions in Oregon, 2017Every mesoscale discussion in 2017

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.