Alert archive / South Dakota / Mesoscale Discussions in 2025

Mesoscale Discussion 1621

July 9, 202510 counties in Nebraska; 5 counties in North Dakota; 17 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Jul 9, 2025, 5:30 PM MDT for 10 counties in Nebraska; 5 counties in North Dakota; 17 counties in South Dakota. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Jul 9, 2025, 5:30 PM MDT (23:30 UTC)
Expired: Jul 9, 2025, 7:00 PM MDT
In force: 90 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 498

All 32 counties

Burleigh County, ND, Emmons County, ND, Grant County, ND, Morton County, ND, Sioux County, ND, Arthur County, NE, Blaine County, NE, Brown County, NE, Cherry County, NE, Grant County, NE, Hooker County, NE, Keya Paha County, NE, Logan County, NE, McPherson County, NE, Thomas County, NE, Bennett County, SD, Campbell County, SD, Corson County, SD, Dewey County, SD, Haakon County, SD, Hughes County, SD, Jackson County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Potter County, SD, Stanley County, SD, Sully County, SD, Todd County, SD, Tripp County, SD, Walworth County, SD, Ziebach County, SD

The radar

The Rapid City radar (KUDX), 179 km from the middle of the area, began a volume at 23:30 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.

Severe Thunderstorm Watch 500Jul 9, 6:35 PM MDT

The nearest sounding before it

Aberdeen, SD (KABR), launched 12:00Z, 11.5 hours before the alert went out and 186 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: 1433 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 106 m²/s²
0-3 km storm-relative helicity: 271 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 4.6

Open this sounding in Storm Lab

The text

As transmitted.

684 
ACUS11 KWNS 092331
SWOMCD
SPC MCD 092330 
SDZ000-NDZ000-NEZ000-100100-

Mesoscale Discussion 1621
NWS Storm Prediction Center Norman OK
0630 PM CDT Wed Jul 09 2025

Areas affected...South-central ND...central SD...and north-central
NE

Concerning...Severe Thunderstorm Watch 498...

Valid 092330Z - 100100Z

The severe weather threat for Severe Thunderstorm Watch 498
continues.

SUMMARY...Isolated/sporadic large hail and embedded severe wind
gusts remain possible across Severe Thunderstorm Watch 498. While
uncertain, there is some potential for eventual upscale growth into
one or more clusters into tonight.

DISCUSSION...Two disorganized clusters with transient/embedded
deeper cores are  drifting slowly east-southeastward across the
Dakotas and northern NE this evening -- where periodic severe wind
gusts and large hail are occurring. Weak large-scale forcing for
ascent and strong buoyancy/steep deep-layer lapse rates have
generally promoted outflow dominant storms with limited large-scale
organization up to this point. Nevertheless, the strong buoyancy and
long/generally straight hodographs (around 40 kt of effective shear)
will continue to promote severe downbursts/outflow and sporadic
large hail with the stronger embedded cores. 

While the weak forcing for ascent casts uncertainty on overall
convective evolution, a gradually strengthening low-level jet may
promote eventual upscale growth into one or more organized clusters
into tonight. Confidence in this scenario is relatively higher for
the southern area of storms currently over southern SD into northern
NE -- as the low-level jet may tend to focus over this general
region amid slightly stronger deep-layer shear. If this evolution
can occur, the risk of severe wind gusts would increase with time,
and a downstream watch would eventually be needed.

..Weinman.. 07/09/2025

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FSD...ABR...BIS...LBF...UNR...

LAT...LON   46990014 46129975 45229956 44219951 43219932 41729957
            41330009 41310092 41320168 41740205 43040179 44910166
            46500184 47180102 47180049 46990014 

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 9, 1:47 PM MDT	Severe Thunderstorm Watch	SPC	Arthur, Blaine, Box Butte, Brown, Cherry, Dawes and 12 more	7 hr
Jul 9, 12:31 PM MDT	Mesoscale Discussion	SPC	Bennett, Butte, Dewey, Haakon, Harding, Jackson and 9 more	119 min

Nearby

Mesoscale Discussions in South Dakota, 2025 Mesoscale Discussions in Nebraska, 2025 Mesoscale Discussions in North Dakota, 2025 Every mesoscale discussion in 2025

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.