July 31st Severe Storms Recap

Thunderstorms developed across northwestern South Dakota around 4 pm on Friday, July 31st and then spread and developed further south and east through the evening across much of central South Dakota and into western portions of the James River Valley. Even though not all the typical ingredients for severe thunderstorms were in place, relatively dry air in the lower levels of the atmosphere promoted the development of strong to severe wind gusts of 50-80 mph. Often times, these winds were associated with thunderstorm outflow boundaries, which can race well out ahead of the parent thunderstorm. Thus, even though the sky doesn't darken and rain/lightning isn't present, damaging winds can still occur. Find more information below. 

Latest storm reports map, from https://t.co/ehBn2PHvPz

Observed rainfall (radar-estimated)

Photos from Redfield at 8:30 pm courtesy of Derek Thompson (left) and from just north of Doland courtesy of Alex Resel (right)

Radar reflectivity loop (7:11 to 7:51 pm CDT) of the storm that produced a measured 78 mph wind gust at Craven's Corner at 7:39 pm CDT. Outflow boundaries (fine lines coming out from this storm and others further west) are clearly visible, and indicate the leading edge of strong winds. 

Listing of storm reports below

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...

..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....

            ..REMARKS..

0700 PM     Tstm Wnd Gst     Selby                   45.50N 100.03W

07/31/2020  E70 MPH          Walworth           SD   Law Enforcement  

0630 PM     Tstm Wnd Gst     1 WNW Glenham           45.54N 100.28W

07/31/2020  E65 MPH          Walworth           SD   Law Enforcement 

0624 PM     Tstm Wnd Gst     4 ESE Akaska            45.31N 100.06W

07/31/2020  M59 MPH          Walworth           SD   Mesonet         

            Mesonet station 209 Lowry (SDDOT).

0616 PM     Tstm Wnd Gst     1 NE Mobridge           45.55N 100.42W

07/31/2020  M68 MPH          Walworth           SD   ASOS            

            ASOS station KMBG Mobridge Muni AP.

0612 PM     Tstm Wnd Gst     7 S Glenham             45.44N 100.29W

07/31/2020  E60 MPH          Walworth           SD   NWS Employee    

            Winds over 60 mph.

0604 PM     Tstm Wnd Dmg     Mobridge                45.54N 100.44W

07/31/2020                   Walworth           SD   Public          

            Power lines down. Time estimated by radar and Mobridge Airport wind gust.

0620 PM     Tstm Wnd Gst     3 SSW Whitlocks Bay Rec 45.01N 100.29W

07/31/2020  M55 MPH          Potter             SD   Mesonet         

            Mesonet station 157 Forest City (SDDOT).

0724 PM     Tstm Wnd Gst     9 NNW Vivian            44.05N 100.33W

07/31/2020  M58 MPH          Lyman              SD   Mesonet         

            Mesonet station 13 Vivian (SDDOT).

0657 PM     Tstm Wnd Gst     2 ENE Pierre            44.38N 100.28W

07/31/2020  M69 MPH          Hughes             SD   ASOS            

            ASOS station KPIR Pierre Muni AP.

0830 PM     Tstm Wnd Gst     9 N Chelsea             45.30N 98.75W

07/31/2020  E60 MPH          Edmunds            SD   Trained Spotter 

            Tree limbs down.

0825 PM     Tstm Wnd Gst     1 NE Mina               45.45N 98.74W

07/31/2020  M56 MPH          Edmunds            SD   Mesonet                      

0739 PM     Tstm Wnd Gst     Cravens Corner          45.45N 98.93W

07/31/2020  M78 MPH          Edmunds            SD   Mesonet         

            Mesonet station 173 Craven (SDDOT).

0730 PM     Tstm Wnd Gst     Roscoe                  45.45N 99.33W

07/31/2020  M56 MPH          Edmunds            SD   Emergency Mngr               

0714 PM     Tstm Wnd Gst     1 ESE Bowdle            45.44N 99.64W

07/31/2020  M59 MPH          Edmunds            SD   Mesonet         

            Mesonet station 216 Bowdle (SDDOT).

0710 PM     Tstm Wnd Gst     3 S Roscoe              45.40N 99.34W

07/31/2020  E70 MPH          Edmunds            SD   Trained Spotter 

            70 plus mph wind gusts from the outflow of a thunderstorm just northeast of this

            location. Radar estimated time.

0602 PM     Tstm Wnd Gst     8 WNW Whitlocks Bay Rec 45.09N 100.42W

07/31/2020  E60 MPH          Dewey              SD   Public          

            Radar estimated time.

0557 PM     Tstm Wnd Gst     7 W Swan Creek Rec Area 45.30N 100.40W

07/31/2020  M56 MPH          Dewey              SD   Public          

            Radar estimated time.

0530 PM     Tstm Wnd Gst     Eagle Butte             45.00N 101.24W

07/31/2020  E55 MPH          Dewey              SD   Public                       

0550 PM     Tstm Wnd Gst     2 SE Mclaughlin         45.80N 100.78W

07/31/2020  M56 MPH          Corson             SD   Mesonet         

            Mesonet station MHTS2 McLaughlin 2 SE (SD Mesonet).

0544 PM     Tstm Wnd Gst     5 WNW Mclaughlin        45.85N 100.91W

07/31/2020  M71 MPH          Corson             SD   Mesonet         

            Mesonet station 205 McLaughlin (SDDOT).

0525 PM     Tstm Wnd Gst     2 WNW Trail City        45.48N 100.78W

07/31/2020  E65 MPH          Corson             SD   Public          

            Estimated 60-70 mph winds along with pea to quarter sized hail. Radar estimated time.

0452 PM     Hail             3 SSW Klein Ranch       45.62N 101.37W

07/31/2020  E1.75 inch       Corson             SD   Public