Tornadoes and Flooding in South Dakota, July 3 to 4, 2019

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
117 PM MDT Wed Jul 3 2019

.DISCUSSION...(This Evening Through Wednesday)
Issued at 115 PM MDT Wed Jul 3 2019

Latest analysis has an upper low over the Pacific Northwest with a
trough digging down the West Coast with weak upper ridging over the
Mississippi Valley region, leaving the western High Plains in a west
southwesterly flow pattern. At the surface, a stationary
boundary/cold front remains draped across southwestern South Dakota
and northwest SD, into eastern North Dakota. Latest satellite trends
shows a CU field over the southern Black Hills, far southwestern SD,
and areas of eastern Perkins and Meade Counties while low clouds
remain in place over the WY Black Hills, northern Black Hills and
southwestern Butte County remain socked in with fog and low clouds.

For this afternoon and tonight, lee cyclogenesis is ongoing along
the lee trough in eastern Wyoming with large-scale forcing ahead of
an approaching shortwave toward the northwestern portion of the
forecast area. Some convective initiation seems imminent across the
current CU fields in eastern WY and western SD, even with the better
flow aloft over the northern half of the forecast area. Should see
storms move off the higher terrain into the forecast area later this
afternoon/early evening as well. With the frontal boundary, steep
lapse rates, MU CAPE of 1500-3000 J/kg, and modest shear, expect
severe storms this afternoon and evening. Primary threat will be
large hail and damaging winds, and transitioning to more of a wind
event later this evening. The bulk of the storms will push east
overnight, but could see more storm activity redeveloping during the
early morning hours.

On Independence Day, could see some morning storms, then clearing
before the next round of storms in the afternoon and evening. Severe
weather will again be possible as strong CAPE and possibly stronger
shear than today is expected.

Overall, this pattern looks to persistent into early next week,
resulting in daily chances of thunderstorms. Some of the storms
during this time will be strong to severe.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1106 AM MDT Wed Jul 3 2019

Lingering MVFR/IFR ceilings over northeastern WY, the northern
Hills, and far northwestern SD should improve to VFR early this
afternoon. Thunderstorms will develop around 21Z, spreading across
much of the CWA through the evening. Some of these storms could be
severe. Behind the storms, low clouds and patchy fog could
develop, especially across northeastern WY and in/around the
Black Hills.

&&

.HYDROLOGY...
Issued at 115 PM MDT Wed Jul 3 2019

No changes to the current flash flood watch. PWs are 175% of
average and soils are saturated, especially across northwestern
SD. Expect some heavy rain possibly across southern SD and areas
just east of the Hills. However, with the better forcing further
north, have opted to leave the watch as is and monitor for
possible warnings later this afternoon and evening.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Flash Flood Watch through late tonight for SDZ001-002-012>014-
     024-025-072-073.

WY...Flash Flood Watch through late tonight for WYZ054-056-057-071.

&&

DISCUSSION...MLS
AVIATION...Pojorlie
HYDROLOGY...MLS

Hazardous Weather Outlook...CORRECTED
National Weather Service Rapid City SD
257 PM MDT Wed Jul 3 2019

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-041300-
Harding-Perkins-Butte-Northern Meade Co Plains-Ziebach-
Northern Black Hills-Northern Foot Hills-Rapid City-
Southern Foot Hills-Central Black Hills-Southern Black Hills-
Custer Co Plains-Pennington Co Plains-Haakon-Fall River-
Oglala Lakota-Jackson-Bennett-Mellette-Todd-Tripp-
Sturgis/Piedmont Foot Hills-Southern Meade Co Plains-
Hermosa Foot Hills-Northern Campbell-Southern Campbell-
Western Crook-Wyoming Black Hills-Weston-Northeastern Crook-
257 PM MDT Wed Jul 3 2019 /357 PM CDT Wed Jul 3 2019/

This Hazardous Weather Outlook is for western South Dakota and
northeastern Wyoming.

.DAY ONE...This Afternoon and Tonight

Scattered strong to severe thunderstorms are possible this
afternoon and evening. Large hail, damaging wind gusts, and heavy
rain are the main severe weather threats, although a couple
tornadoes are also possible.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

There is a chance of showers and thunderstorms each day. Severe
thunderstorms are possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible today.

&&

Stay tuned to NOAA weather radio for further updates...or check
our web site at weather.gov/rapidcity

<!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>

<!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>