Alert archive / South Dakota / Mesoscale Discussions in 2021
Mesoscale Discussion 1601
The Storm Prediction Center issued this mesoscale discussion at Aug 25, 2021, 3:02 PM CDT for Lyon County, Plymouth County, Sioux County, Iowa; Boyd County, Knox County, Nebraska; 8 counties in South Dakota. It was in force for 88 min.
The area
The outline as issued.
The facts
- Issued
- Aug 25, 2021, 3:02 PM CDT (20:02 UTC)
- Expired
- Aug 25, 2021, 4:30 PM CDT
- In force
- 88 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Lyon County, IA, Plymouth County, IA, Sioux County, IA, Boyd County, NE, Knox County, NE, Bon Homme County, SD, Charles Mix County, SD, Clay County, SD, Hutchinson County, SD, Lincoln County, SD, Turner County, SD, Union County, SD, Yankton County, SD
The radar
The Sioux Falls radar (KFSD), 95 km from the middle of the area, began a volume at 20:03 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
Aberdeen, SD (KABR), launched 12:00Z, 8.0 hours before the alert went out and 208 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1403 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- -140 m²/s²
- 0-3 km storm-relative helicity
- -20 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
124 ACUS11 KWNS 252003 SWOMCD SPC MCD 252002 IAZ000-MNZ000-SDZ000-NEZ000-252130- Mesoscale Discussion 1601 NWS Storm Prediction Center Norman OK 0302 PM CDT Wed Aug 25 2021 Areas affected...northeast Nebraska...southeast South Dakota and northwest Iowa Concerning...Severe potential...Watch unlikely Valid 252002Z - 252130Z Probability of Watch Issuance...20 percent SUMMARY...A small storm cluster along the southeast South Dakota / northeast Nebraska border may produce a few locally strong wind gusts and some hail next couple hours. Threat does not appear sufficient to warrant a WW. DISCUSSION...This afternoon a small storm cluster is situated along the NE/SD border moving east at around 40 kt. Sub-severe wind gusts up to 45 mph have been reported. Activity is developing above a stable near-surface layer within a weak warm advection regime and updrafts based around 700 mb. Near-surface temperatures are modestly warmer with larger temperature / dewpoint spreads downstream of the storms, suggesting a somewhat greater threat for wind gusts might be realized. Also steep mid-level lapse rates, moderate instability and up to 45 kt effective bulk shear may support some threat for hail. There is some chance the updrafts could become rooted in the surface layer farther downstream. However, degree of surface-based convective inhibition associated with a warm layer aloft lowers confidence in this scenario and how long storms will persist. Nevertheless, at least for the next couple hours, activity may remain capable of producing a few strong gusts and hail as it continues east. ..Dial/Kerr.. 08/25/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD...OAX...LBF... LAT...LON 43139898 43509786 43569590 42739579 42559869 43139898
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 24, 11:18 PM CDT | Mesoscale Discussion | SPC | Butler, Dodge, Douglas, Polk, Sarpy, Saunders and 1 more | 117 min |
Nearby
Mesoscale Discussions in South Dakota, 2021Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Nebraska, 2021Every mesoscale discussion in 2021
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.