Heavy Rain and Flash Flooding Concerns in California; Heavy Snow in the Sierra

An atmospheric river will bring heavy rainfall to lower elevations of California this week, and heavy snow to the Sierra Nevada mountains. Flash flooding, some of which may be locally considerable, will be a concern on the western foothills of the Sierra Nevada mountains through Tuesday. Landslides, rockfalls and mudslides are possible in the Southern California mountains. Read More >

Overview

On July 8, 2021, a powerful supercell thunderstorm tracked from extreme southeastern Montana to just east of the Black Hills and into north-central Nebraska. This storm made a direct hit on the NWS Rapid City radar just north of New Underwood, South Dakota. Hail up to tennis ball size and wind gusts up to 70 mph produced damaging wind-driven hail that affected much of the storm's path. Satellite images revealed vegetation damage several days after the hailstorm.

July 9, 2021 KUDX WSR-88D Radar Dome Damage

554 PM MDT July 8, 2021 0.5 Degree Base Reflectivity as the supercell hit the Radar Dome

Photos
Radar, Lightning, Satellite
Storm Reports
Environment

Photos

NWS Radar Dome near New Underwood, SD, and Hailstorm Aftermath


July 9, 2021 KUDX WSR-88D Radar Dome	July 11, 2021 KUDX WSR-88D Inside The Radar Dome	July 9, 2021 Broken Exhaust Pipe at KUDX WSR-88D Radar	July 9, 2021 Wind-Driven Hail Damage to Steel Door at KUDX WSR-88D Radar

Hey so ya'll might have heard there was this supercell in SD a couple weeks back... ;) Here's the story: it was spectacular, moving incredibly fast, and almost totaled all of our cars - but it would have been worth it. The End.

Faith, SD - 7.8.21#sdwx #StormHour pic.twitter.com/Jtx8JhE4Sa
— Jen Walton (@mejenwalton) July 24, 2021

2” hail just north of Bison, SD @NWSRapidCity pic.twitter.com/K1cj2PB4hC
— Adam Lucio (@AdamLucioWX) July 9, 2021

Quick DSLR edit from shortly after sunset tonight. Forgot I still had my polarizer on but I kinda like the long exposure here showing the rapid motion within this powerful, fast-moving supercell. A high Plains Earth-eater classic! #sdwx pic.twitter.com/suGRJnDtGd
— Jim Tang (@wxmann) July 9, 2021

THU-6:09 PM: Tennis ball hail going sideways at 60-70 MPH has damaged multiple vehicles on the highway a mile East of New Underwood on I-90. Use extreme caution as this storm races to the southeast. @NWSRapidCity pic.twitter.com/SRk5XrCBJI
— Brant Beckman (@BrantBeckmanwx) July 9, 2021

THU-4:58 PM: This rotating severe thunderstorm has dropped golf ball size hail in Newell, SD and is pressing southeast towards rural Meade County. Stay alert @NWSRapidCity pic.twitter.com/f2JH8mxiK6
— Brant Beckman (@BrantBeckmanwx) July 8, 2021

Radar, Lightning, Satellite


510 PM MDT July 8, 2021 0.5 Degree Base Reflectivity (large three body scatter spike)	549 PM MDT July 8, 2021 0.5 Degree Base Reflectivity	552 PM MDT July 8, 2021 0.5 Degree Base Reflectivity	554 PM MDT July 8, 2021 0.5 Degree Base Reflectivity


557 PM MDT July 8, 2021 0.5 Degree Base Reflectivity	24-h MRMS MESH Tracks	24-h Cloud-to-Ground NLDN Lightning Flashes Ending 7/9/2021 at 6 am MDT	GOES-East 24-h Cloud Flash Points (6am July 8 to 6am July 9, 2021)

July 8, 2021 502 PM to 602 PM MDT 0.5 Degree Base Reflectivity Radar Loop

July 8, 2021 314 PM to 829 PM MDT 0.5km Visible Satellite Loop

Storm Reports



...MAXIMUM HAIL SIZE SORTED BY MAGNITUDE July 8, 2021...

LOCATION                      MAX SIZE    COMMENTS
                               IN/S/

5 N Scenic SD                  2.75        630 PM 7/08/2021
2 E New Underwood SD           2.50        600 PM 7/08/2021
12 S Faith SD                  2.50        907 PM 7/08/2021
1 N Bison SD                   2.00        704 PM 7/08/2021
8 WNW Usta SD                  2.00        824 PM 7/08/2021
14 SSE Hereford SD             1.75        544 PM 7/08/2021
3 W White River SD             1.50       1130 PM 7/08/2021
6 W Martin SD                  1.50        755 PM 7/08/2021
8 WSW Lodgepole SD             1.50        726 PM 7/08/2021
1 ENE Bridger SD               1.00        940 PM 7/08/2021
6 NNW Kyle SD                  1.00        713 PM 7/08/2021
Dupree SD                      1.00        840 PM 7/08/2021
8 WSW Hereford SD              1.00        528 PM 7/08/2021
7 N Belvidere SD               1.00       1050 PM 7/08/2021