Alert archive / South Dakota / Severe Thunderstorm Watches in 2017
Severe Thunderstorm Watch 427
The Storm Prediction Center issued this severe thunderstorm watch at Jul 20, 2017, 10:26 PM CDT for 11 counties in South Dakota. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 20, 2017, 10:26 PM CDT (03:26 UTC)
- Expired
- Jul 21, 2017, 1:28 AM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
Counties Brown County, SD, Campbell County, SD, Edmunds County, SD, Faulk County, SD, Hand County, SD, Hyde County, SD, McPherson County, SD, Potter County, SD, Spink County, SD, Sully County, SD, Walworth County, SD
The radar
The Aberdeen radar (KABR), 87 km from the middle of the area, began a volume at 03:26 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
1 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 10:41 PM CDT | Severe Thunderstorm Warning | ABR | Campbell, Dewey, Edmunds, McPherson, Potter, Sully and 1 more | 64 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Aberdeen, SD (KABR), launched 00:00Z, 3.4 hours before the alert went out and 99 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
- 25 J/kg
- Mixed-layer CIN
- -379 J/kg
- Mixed-layer LCL
- 2211 m above ground
- 0-6 km bulk shear
- 45 kt
- 0-1 km storm-relative helicity
- 13 m²/s²
- 0-3 km storm-relative helicity
- -37 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 7:31 PM CDT | Mesoscale Discussion | SPC | Campbell, Corson, Dewey, Meade, Perkins, Ziebach | 89 min |
| Jul 20, 11:25 PM CDT | Mesoscale Discussion | SPC | Brown, Campbell, Edmunds, Faulk, McPherson, Potter and 3 more | 65 min |
| Jul 21, 2:20 PM CDT | Mesoscale Discussion | SPC | Brown, Campbell, Day, Edmunds, Faulk, McPherson and 6 more | 2 hr |
| Jul 21, 3:07 PM CDT | Severe Thunderstorm Watch | SPC | Brown, Campbell, Corson, Day, Dewey, Edmunds and 11 more | 10 hr |
| Jul 21, 3:53 PM CDT | Mesoscale Discussion | SPC | Brown, Campbell, Corson, Day, Dewey, Edmunds and 8 more | 97 min |
| Jul 21, 6:25 PM CDT | Mesoscale Discussion | SPC | Grant, Marshall, Roberts | 95 min |
Nearby
Severe Thunderstorm Watches in South Dakota, 2017Every severe thunderstorm watch 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; radar from the NEXRAD Level II archive.