Back-to-back powerful Pacific storm systems to impact the Pacific Northwest and northern California through the end of this week with heavy rain, flooding, strong winds, and higher elevation mountain snow. A strong, long-duration atmospheric river will accompany the Pacific storms, bringing excessive rainfall and flash flooding to southwest Oregon and northwest California through the week. Read More >
Overview
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Storms tracked across north central and northeast South Dakota during the evening hours of July 24th and into July 25th. Developing in a very moisture rich atmosphere, the storms were able to produce very heavy rain in a short amount of time, especially over parts of northeastern McPherson County, northern Brown County and far northern Marshall County. Rainfall amounts ranged from 4 to 10 inches, with localized heavier amounts reported. The heavy rain lead to significant overland flooding as well as flooding on Elm Lake and subsequent flooding downstream along the Elm River. Many roads were underwater or completely washed out. There were reports of boats and docks submerged with others freely floating on Elm Lake. The river gauge on the Elm River, just below Elm Lake, (ERFS2) reached a record stage of 19.56 feet by the afternoon of July 25th. The Elm River at Westport (WESS2) crested at a major flood stage of 20.45 feet late on July 26th. |
 Drone Photo of the Elm Lake Spillway. Photo Credit: Frederick Fire Department |
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| Overland Flooding in NE McPherson County. Photo Credit: McPherson County Emergency Management. | McPherson County Highway 23 Washout. Video Credit: McPherson County Emergency Management. | Road Damage Near Elm Lake. Photo Credit: Elm Lake Association |
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| Water To the Bottom of a Bridge At Elm Lake. Photo Credit: Frederick Fire Department | Drone Photo of the South End of Elm Lake, Spillway to the Left. Photo Credit: Frederick Fire Department. | Full Rain Gauge (10+ inches) 2 Miles West of Elm Lake. Photo Credit of Steffanie Mohror. |
Flooding
Hydrographs
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| Elm River Below Elm Lake Hydrograph (ERFS2) | Elm River At Westport Hydrograph (WESS2) | Elm River at Ordway Hydrograph (ORDS2) | James River At Columbia Hydrograph (CMBS2) |
Radar/Photos
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| Radar Loop 7:00 pm CDT July 24, 2020 to 1:00 AM CDT July 25, 2020. | Preliminary Rainfall Reports | Radar Estimates and Rainfall Observations | Map of Streams and Tributaries That Flow Into the Elm River |
Storm Reports
PRELIMINARY LOCAL STORM REPORT...SUMMARY NATIONAL WEATHER SERVICE ABERDEEN SD 136 PM CDT SAT JUL 25 2020 ..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON... ..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE.... ..REMARKS.. 1154 PM TSTM WND GST 9 E SPRING CREEK COLONY 45.91N 98.69W 07/24/2020 M59 MPH BROWN SD MESONET PERSONAL WEATHER STATION. 1019 PM TSTM WND GST 9 E SPRING CREEK COLONY 45.91N 98.69W 07/24/2020 M54 MPH BROWN SD MESONET PERSONAL WEATHER STATION PEAK GUST. 0724 PM TSTM WND GST 2 N HERREID 45.87N 100.07W 07/24/2020 M54 MPH CAMPBELL SD MESONET MESONET STATION 50 HERREID (SDDOT). 1020 PM TSTM WND GST 7 N FREDERICK 45.93N 98.53W 07/24/2020 M53 MPH BROWN SD MESONET PEAK GUST. 0722 PM TSTM WND GST 5 SW KENNEBEC 43.86N 99.93W 07/24/2020 M53 MPH LYMAN SD PUBLIC 1.95 INCHES OF RAIN AND GUSTS MEASURED VIA PERSONAL WEATHER STATION. 0900 AM HEAVY RAIN 10 NW FREDERICK 45.91N 98.67W 07/25/2020 M7.80 INCH BROWN SD PUBLIC STORM TOTAL RAINFALL. 12 HOUR REPORT. 0830 AM HEAVY RAIN 9 NW FREDERICK 45.92N 98.64W 07/25/2020 M7.75 INCH BROWN SD PUBLIC STORM TOTAL RAINFALL. 1240 AM HEAVY RAIN 9 E SPRING CREEK COLONY 45.91N 98.69W 07/25/2020 M7.04 INCH BROWN SD MESONET PERSONAL WEATHER STATION STORM TOTAL RAINFALL. 1240 AM HEAVY RAIN 2 ENE SPRING CREEK COLO 45.92N 98.85W 07/25/2020 M6.86 INCH MCPHERSON SD MESONET PERSONAL WEATHER STATION STORM TOTAL RAINFALL. 0800 AM HEAVY RAIN 6 ENE SPRING CREEK COLO 45.93N 98.76W 07/25/2020 M6.75 INCH MCPHERSON SD CO-OP OBSERVER ROADS TO THE SOUTH FLOODED FOR THE FIRST TIME EVER SINCE THE OBSERVER HAS BEEN THERE. 0833 AM HEAVY RAIN 4 NW FREDERICK 45.87N 98.57W 07/25/2020 M6.00 INCH BROWN SD PUBLIC 12 HOUR RAINFALL. 1205 AM HEAVY RAIN SPRING CREEK COLONY 45.91N 98.88W 07/25/2020 E6.00 INCH MCPHERSON SD PUBLIC 1100 PM HEAVY RAIN 2 ENE SPRING CREEK COLO 45.92N 98.85W 07/24/2020 M5.00 INCH MCPHERSON SD MESONET STILL RAINING. PERSONAL WEATHER STATION. 1110 PM HEAVY RAIN 9 E SPRING CREEK COLONY 45.91N 98.69W 07/24/2020 M3.21 INCH BROWN SD PUBLIC STILL RAINING. PERSONAL WEATHER STATION. 0700 AM HEAVY RAIN 3 NNE IONA 43.58N 99.39W 07/25/2020 M3.10 INCH LYMAN SD COCORAHS COCORAHS STATION SD-LY-31 IONA 2 NE. 0700 AM HEAVY RAIN 8 ENE HECLA 45.92N 98.00W 07/25/2020 M3.02 INCH BROWN SD CO-OP OBSERVER CO-OP OBSERVER STATION BRTS2 HECLA 5 NE. 0700 AM HEAVY RAIN 8 WNW IONA 43.59N 99.57W 07/25/2020 M2.90 INCH LYMAN SD COCORAHS COCORAHS STATION SD-LY-7 OACOMA 17 SSW. 0700 AM HEAVY RAIN 9 W FREDERICK 45.84N 98.70W 07/25/2020 M2.72 INCH BROWN SD CO-OP OBSERVER CO-OP OBSERVER STATION ERFS2 8.3 SE FORBES. 0700 AM HEAVY RAIN 7 WNW HECLA 45.92N 98.29W 07/25/2020 M2.55 INCH BROWN SD COCORAHS COCORAHS STATION SD-BR-4 HECLA 7 WNW. 0700 AM HEAVY RAIN 6 SW OACOMA 43.75N 99.48W 07/25/2020 M2.22 INCH LYMAN SD COCORAHS COCORAHS STATION SD-LY-15 OACOMA 5 WSW. 0700 AM HEAVY RAIN 8 SSW KENNEBEC 43.79N 99.92W 07/25/2020 M1.84 INCH LYMAN SD COCORAHS COCORAHS STATION SD-LY-27 KENNEBEC 8 SSW. 0700 AM HEAVY RAIN 4 WNW HILLHEAD 45.86N 97.46W 07/25/2020 M1.81 INCH MARSHALL SD COCORAHS COCORAHS STATION SD-MR-10 VEBLEN 8 W. 1015 AM FLOOD 9 W FREDERICK 45.84N 98.70W 07/25/2020 BROWN SD FIRE DEPT/RESCUE MULTIPLE ROADS IN NORTHWESTERN BROWN COUNTY WITH WATER OVER THEM. BROWN COUNTY5 107TH IS CLOSED WEST OF 378TH AVENUE. 0820 AM FLOOD 9 E SPRING CREEK COLONY 45.90N 98.69W 07/25/2020 BROWN SD EMERGENCY MNGR DOCKS AND PONTOONS FLOATING DUE TO HIGH WATER LEVEL ON ELM LAKE. MULTIPLE ROADS UNDER WATER. 0310 AM FLASH FLOOD 7 SE SPRING CREEK COLON 45.84N 98.77W 07/25/2020 MCPHERSON SD EMERGENCY MNGR EMERGENCY MANAGER REPORTS MANY COUNTY ROADS UNDER WATER. COUNTY ROAD 23 (371ST AVE), IN PARTICULAR, HAS AN AREA VERY DEEP UNDER WATER. NO TRAVEL ADVISED IN NORTHEAST MCPHERSON COUNTY EARLY THIS MORNING!.
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