Overview
An area of low pressure and cold front moved through the Northern Plains during the afternoon and evening hours of August 11, 2019. This storm system, combined with above average water in the atmosphere, created numerous thunderstorms across most of western South Dakota. Runoff from the heavy rain caused flash flooding and flooding across portions of Oglala Lakota County. Three to five inches of rain was reported between Porcupine, Sharps Corner, and Kyle. A large amount of the precipitation fell over Iron Cloud Canyon, causing flash flooding of BIA 27 between Evergreen and Gooseneck Road. Several feet of fast moving water inundated BIA 27 and caused significant flooding of Porcupine Creek. As the flood waters continued along Porcupine Creek, BIA 2 just east of Sharps Corner was inundated by the morning of August 12th. Additional flooding along Porcupine Creek continued downstream to the White River.
Flooding
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Photos and Videos
| Facebook Video from OST Emergency Management of BIA 27 posted at 745 pm on 8/11/2019 |
| Twitter Video from @Tokalasina of BIA 27 |
— me (@tokalasina) August 12, 2019 |
| Facebook Video from Jess Killsback from KILI Radio 90.1 FM of Flooding below Evergreen |
| Twitter Video from Martin Vol Fire department of BIA 2 Hwy near Sharps Corner taken 8/12/2019 |
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| Twitter Video from Martin Vol Fire Department by Jack Pourier Place in the Sharps Corner area |
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| Facebook Photo from Fall River County Sheriff's Office of Rock Slide in Sheps Canyon |
Rainfall and Storm Reports
The storm reports listed below are in descending order and may not
necessarily be the final storm reports.
Rain amounts (inches)
AMOUNT LOCATION ST COUNTY TIME
------ ----------------------- -- -------------- -------
3.42 6 WNW SHADEHILL SD PERKINS 0600 AM
2.82 7 W SHADEHILL SD PERKINS 0650 PM
HEAVY RAIN FELL FROM 0620 TO 0650 PM MDT.
2.81 5 NE PORCUPINE SD OGLALA LAKOTA 0800 AM
24 HOUR TOTAL
2.31 2 WSW HAMILL SD TRIPP 0630 AM
2.25 3 E WASTA SD PENNINGTON 0700 AM
1.84 5 NE PORCUPINE SD OGLALA LAKOTA 0641 PM
RAINFALL BETWEEN 541 PM to 641 PM
1.80 4 NE MARTIN SD BENNETT 1043 PM
1.80 1 SW SHADEHILL SD PERKINS 0800 PM
RAINFALL FROM 600 PM TO 800 PM
1.80 HERMOSA SD CUSTER 0800 PM
1.70 9 SW ANGOSTURA RES SD FALL RIVER 0800 AM
24 HOUR TOTAL
1.70 1 N IDEAL SD TRIPP 0700 AM
1.66 7 WSW FOLSOM SD CUSTER 0530 AM
1.58 9 SW ANGOSTURA RES SD FALL RIVER 0600 PM
FELL IN 45 MINUTES
1.57 1 NNE EDGEMONT SD FALL RIVER 0800 AM
24 HOUR TOTAL
1.57 3 WNW KADOKA SD JACKSON 0500 AM
1.55 1 NNE EDGEMONT SD FALL RIVER 0600 PM
FELL IN ONE HOUR
1.54 2 ENE WASTA SD PENNINGTON 0830 PM
FELL IN 1.5 HOURS
1.49 2 NNW ANGOSTURA RES SD FALL RIVER 0800 AM
24 HOUR TOTAL
1.49 3 SE FARMINGDALE SD PENNINGTON 0800 PM
FELL IN 1.5 HOURS
1.39 2 NNW ANGOSTURA RES SD FALL RIVER 0615 PM
FELL IN 1.5 HOURS
1.34 1 WSW WINNER SD TRIPP 0700 AM
1.28 1 S DWTN RAPID CITY SD PENNINGTON 0815 PM
STORM TOTAL RAINFALL
1.24 1 NNE EDGEMONT SD FALL RIVER 0600 AM
1.23 2 SW NORRIS SD MELLETTE 0700 AM
1.17 4 W MARTIN SD BENNETT 0921 PM
STORM TOTAL RAINFALL
1.08 3 ENE KYLE SD OGLALA LAKOTA 0700 AM
1.05 8 E MARTIN SD BENNETT 0700 AM
Hail reports listed by size (inches)
SIZE LOCATION ST COUNTY TIME
------ ----------------------- -- -------------- -------
1.00 LUDLOW SD HARDING 0532 PM
A LOT OF PEA SIZE HAIL WITH A FEW NICKELS AND
QUARTERS
1.00 5 W SHARPS CORNER SD OGLALA LAKOTA 0355 PM
Tstm wind reports listed by speed (mph)
SPEED LOCATION ST COUNTY TIME
------ ----------------------- -- -------------- -------
73.00 5 NE PORCUPINE SD OGLALA LAKOTA 0630 PM
70.00 WALL SD PENNINGTON 0730 PM
67.00 3 WSW FAIRBURN SD CUSTER 0625 PM
66.00 10 W EDGEMONT SD FALL RIVER 0459 PM
61.00 3 E PHILIP SD HAAKON 0809 PM
60.00 MARTIN SD BENNETT 0750 PM
60.00 OGLALA SD OGLALA LAKOTA 0615 PM
60.00 1 W EDGEMONT SD FALL RIVER 0508 PM
PEA SIZE HAIL...WIND GUSTS 50 TO 60 MPH
59.00 1 NE WINNER SD TRIPP 1053 PM
55.00 8 WNW FAIRBURN SD CUSTER 0620 PM
54.00 4 E CACTUS FLAT SD JACKSON 0745 PM
54.00 3 NNW SCENIC SD PENNINGTON 0702 PM
52.00 8 W JEWEL CAVE SD CUSTER 0524 PM
51.00 9 SW BATESLAND SD OGLALA LAKOTA 0700 PM
50.00 NEW UNDERWOOD SD PENNINGTON 0700 PM
Radar and Environment
| Figure 1: Radar Loop from Noon to Midnight on August 11, 2019 (for higher resolution, please view on YouTube) |
The near-storm environment on the afternoon of August 11, 2019 was favorable for slow-moving thunderstorms capable of heavy rainfall. Precipitable water (a measure of total atmospheric moisture content) values were just above the 90th percentiles, meaning that moisture content was within the upper 10% of data on record for this time of year.
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| Figure 2: August 11, 2019 upper-air sounding for Rapid City, SD at 1 PM (19Z). PW (precipitable water) of 1.19 in; daily mean 0.86 in and moving average is 0.79 in |
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