Alert archive / South Dakota / Mesoscale Discussions in 2004

Mesoscale Discussion 1740

July 20, 20044 states

The Storm Prediction Center issued this mesoscale discussion at Jul 20, 2004, 2:16 PM CDT for 4 states. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued
Jul 20, 2004, 2:16 PM CDT (19:16 UTC)
Expired
Jul 20, 2004, 4:15 PM CDT
In force
119 min
Issued by
the Storm Prediction Center
All 55 counties

Lyon County, IA, Monona County, IA, Plymouth County, IA, Sioux County, IA, Woodbury County, IA, Nobles County, MN, Rock County, MN, Antelope County, NE, Boone County, NE, Boyd County, NE, Burt County, NE, Cedar County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Garfield County, NE, Holt County, NE, Knox County, NE, Loup County, NE, Madison County, NE, Pierce County, NE, Platte County, NE, Rock County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, Wheeler County, NE, Aurora County, SD, Beadle County, SD, Bon Homme County, SD, Brule County, SD, Buffalo County, SD, Charles Mix County, SD, Clay County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hand County, SD, Hanson County, SD, Hutchinson County, SD, Hyde County, SD, Jerauld County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Moody County, SD, Sanborn County, SD, Turner County, SD, Union County, SD, Yankton County, SD

The radar

The Sioux Falls radar (KFSD), 138 km from the middle of the area, began a volume at 19:20 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

Aberdeen, SD (KABR), launched 12:00Z, 7.3 hours before the alert went out and 168 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, Aberdeen, SD at 12:00Z on 2004-07-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 16 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, Aberdeen, SD at 12:00Z on 2004-07-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 6 square meters per square second.1939Sfc1 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
16 J/kg
Mixed-layer CIN
-354 J/kg
Mixed-layer LCL
1535 m above ground
0-6 km bulk shear
14 kt
0-1 km storm-relative helicity
6 m²/s²
0-3 km storm-relative helicity
127 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 20, 5:35 PM CDTMesoscale DiscussionSPCClinton, Dubuque, Jackson, Jones, Scott55 min
Jul 20, 6:00 PM CDTSevere Thunderstorm WatchSPCClinton, Dubuque, Jackson, Scott4 hr
Jul 20, 6:08 PM CDTMesoscale DiscussionSPCClinton, Dubuque, Jackson, Jones, Scott2 hr
Jul 20, 2:40 PM CDTTornado WatchSPCAntelope, Boyd, Cedar, Cuming, Dixon, Garfield and 9 more6 hr
Jul 20, 6:30 PM CDTMesoscale DiscussionSPCAntelope, Boyd, Cedar, Dixon, Holt, Knox and 4 more90 min
Jul 20, 3:28 PM CDTMesoscale DiscussionSPCCampbell, Corson, Dewey, Harding, Perkins, Potter and 2 more2 hr
Jul 20, 3:55 PM CDTSevere Thunderstorm WatchSPCCampbell, Corson, Dewey, Harding, McPherson, Perkins and 3 more6 hr

Nearby

Mesoscale Discussions in South Dakota, 2004Mesoscale Discussions in Nebraska, 2004Mesoscale Discussions in Iowa, 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.