Flooding in South Dakota, May 1 to 31, 2020

Name: Flooding in South Dakota, May 1 to 31, 2020
Start: 2020-05-01T00:00
End: 2020-05-31T23:59
Location: South Dakota

May 1 to 31, 2020 · NWS FSD · 9 events in 7 counties and zones

50 inches), high flow continued due to routing water downstream from northeast South Dakota where rainfall was from 3 to 4 inches during the month.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
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Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 9

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS FSD wrote it up.

Despite mainly normal to below normal rainfall in the mid and lower James River Basin during May (averaging 1.50 to 2.50 inches), high flow continued due to routing water downstream from northeast South Dakota where rainfall was from 3 to 4 inches during the month.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Sioux Falls, SD wrote its last area forecast discussion before the first event at Apr 30, 9:57 PM CST, 2 hours 3 minutes earlier.

Area forecast discussion, Apr 30, 9:57 PM CST, 2 hours 3 minutes before

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1057 PM CDT Thu Apr 30 2020

.SHORT TERM...(This Evening through Friday)
Issued at 247 PM CDT Thu Apr 30 2020

Warmer air builds into the region tonight, amidst ridging aloft and
southerly returns flow. This combined with increased cloud cover
will bring overnight lows mainly in the 50s. Most CAMs suggest light
rain showers or sprinkles cannot be ruled out along and west of the
James River Valley late tonight and along and northeast of the
Buffalo Ridge in MN on Friday morning. While warm air advection and
a mid level shortwave will bring increased cloud cover late tonight
through early Friday, but model soundings suggest lift will be too
meager to overcome dry lower levels. Kept a mention of sprinkles and
light rain showers in these regions overnight and into Friday
morning, but suspect this activity will result mainly in virga and
very little if any measurable rain.

Friday will bring notably warmer and breezy weather with
temperatures peaking about 5 to 10 degrees warmer than Thursday. A
shortwave trough aloft tracks east along the international border,
dragging a N-S surface trough and narrow unstable warm sector with
40s and 50s dew points into the region. Expect increasing pressure
gradient winds Friday morning with soundings suggesting peak gusts
around 30 mph, but there will be a subtle weakening in winds
associated with the surface trough moving through during the day.

Given the recent model trend for underforecasting mixing the
boundary layer, went with slightly higher max temperatures, wind
gusts, and lower humidity than a model consensus would suggest. This
drier forecast gave afternoon minimum humidity levels in the 20s to
lower 30s, when winds would be weaker across the main area of
concern for near critical fire weather conditions - northwest IA and
southwest MN. Could see gusts in the 20s in the afternoon, but it
seems unlikely to maintain sustained winds in the 20s so will hold
off on any headlines. Expect winds to weaken diurnally Friday night
as the pressure gradient relaxes.

.LONG TERM...(Friday Night through Thursday)
Issued at 247 PM CDT Thu Apr 30 2020

For Saturday through early Sunday, cannot completely rule out
periodic rain showers south of the I-90 corridor as a mid level
front and broad lift from jet streaks aloft passes through the
region. With more cloud cover in the region and northerly flow on
Saturday, expect cooler but still comfortable spring weather with
highs in the upper 60s to mid 70s.

For late Sunday through Wednesday, an active, wetter northwest flow
aloft pattern develops with several rounds of off and on showers and
thunderstorms expected in the region. Low confidence in any details
regarding these disturbances with the GFS being an outlier (higher
rainfall coverage and amounts). Northwest flow coupled with
increased cloud cover will bring overall cooler weather with
temperatures remaining near normal values.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1052 PM CDT Thu Apr 30 2020

Mid and high-level cloud cover will increase overnight, with a
few sprinkles possible. Very dry low levels will likely prevent
any measurable precipitation, by evaporation-cooled air could
cause some localized surface wind gusts overnight. A strong low
level jet will increase wind shear above the nocturnal inversion,
with about 40 kt of southerly shear at 2000 ft AGL. Shear ends
around sunrise, and surface winds increase during the morning as
daytime mixing increases. Breezy conditions with gusts 2o to 30 kt
last throughout the day with winds shifting to northwesterly as a
dry cold front moves through.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

SHORT TERM...BP
LONG TERM...BP
AVIATION...VandenBoogart

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

9 flood. Local standard time, as filed.

Flood, Beadle

When: May 1, 12:00 AM CST to May 31, 11:59 PM CST
Where: Beadle County, 3.44 mi E of Hitchcock to 5.41 mi E of Broadland
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 44.630, -98.330

A continuation of flooding from April, the James River at Huron (gage site HURS2) resided in moderate flood stage most of the month, with a peak on May 17 at 2.78 feet above flood stage. Several county and township roads remained inundated. The river remained in minor flood stage at the end of the month.

Flood, Sanborn

When: May 1, 12:00 AM CST to May 31, 11:59 PM CST
Where: Sanborn County, 10.36 mi S of Huron to 11.94 mi S of Huron
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 44.200, -98.220

A continuation of flooding from April, the James River near Forestburg (gage site FORS2) began the month in moderate flood at 2.09 feet above flood stage. After slipping back into minor flood, the river rebounded from mid-month rains into moderate flood to crest 2.16 feet above flood stage on May 25. Numerous county and township roads near the gage were inundated. The river remained at minor flood stage at the end of the month.

Flood, Sanborn

When: May 1, 12:00 AM CST to May 31, 11:59 PM CST
Where: Sanborn County, 2.13 mi NNE of Letcher to 6.28 mi SSE of Letcher
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 43.930, -98.120

A continuation of flooding from April, the James River at Mitchell (gage site JRMS2) began the month at a peak of 2.74 feet above flood stage. After slowly falling through mid-month, a late-month rise in levels resulted in a secondary crest at 2.55 feet above flood stage on May 24. Impacts were generally limited to flooding of agricultural lands near the river. The river remained at minor flood stage at the end of the month.

Flood, Davison

When: May 1, 12:00 AM CST to May 31, 11:59 PM CST
Where: Davison County, 4.92 mi N of Loomis to 6.39 mi S of Ethan
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 43.851, -98.092

A continuation of flooding from April, the James River at Mitchell (gage site JRMS2) began the month at a peak of 2.74 feet above flood stage. After slowly falling through mid-month, a late month rise in levels resulted in a secondary crest at 2.55 feet above flood stage on May 24. Impacts were generally limited to flooding of agricultural lands near the river. The river remained at minor flood stage at the end of the month.

Flood, Hanson

When: May 1, 12:00 AM CST to May 31, 11:59 PM CST
Where: Hanson County, 4.22 mi NW of Plano to 3.78 mi W of Rockport
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 43.851, -97.967

A continuation of flooding from April, the James River at Mitchell (gage site JRMS2) began the month at a peak of 2.74 feet above flood stage. After slowly falling through mid-month, a late month rise in levels resulted in a secondary crest at 2.55 feet above flood stage on May 24. Impacts were generally limited to flooding of agricultural lands near the river. The river remained at minor flood stage at the end of the month.

Flood, Hutchinson

When: May 1, 12:00 AM CST to May 31, 11:59 PM CST
Where: Hutchinson County, 2.41 mi NE of Dimock to 5.37 mi SSE of Milltown
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 43.499, -97.953

A continuation of flooding from April, the James River at Mitchell (gage site JRMS2) began the month at a peak of 2.74 feet above flood stage. After slowly falling through mid-month, a late month rise in levels resulted in a secondary crest at 2.55 feet above flood stage on May 24. Impacts were generally limited to flooding of agricultural lands near the river. The river remained at minor flood stage at the end of the month.

Flood, Hutchinson

When: May 1, 12:00 AM CST to May 31, 6:30 PM CST
Where: Hutchinson County, 3.15 mi SSE of Milltown to 2.89 mi S of Olivet
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 43.380, -97.770

A continuation of flooding from April, the James River near Scotland (gage site SCOS2) began the month with a peak in minor flood at 0.58 feet above flood stage on May 1, before slowly falling below flood stage on May 9. Mid-May rains would return the river above flood stage, with a crest for the month at 0.81 feet above flood stage on May 26. Significant agricultural flooding continued through much of the month.

Flood, Bon Homme

When: May 1, 12:00 AM CST to May 31, 6:30 PM CST
Where: Bon Homme County, 2.49 mi ENE of Scotland to 4.84 mi E of Scotland
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 43.169, -97.688

Flood, Yankton

When: May 1, 12:00 AM CST to May 31, 6:30 PM CST
Where: Yankton County, 9.25 mi WNW of Jamesville to 4.79 mi NNW of Lesterville
Cause: Heavy Rain
Reported by: River/Stream Gage
Coordinates: 43.169, -97.638

What these are

Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in South Dakota in 2020 Every state in 2020 This day in weather history Warnings in South Dakota, May 2020

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 886462, 886463, 886465, 886466, 886468, 886469, 886472, 886473, 886474.