Flash Flood Warning 7, NWS Sioux Falls, SD

067 
WGUS73 KFSD 030844
FFSFSD

Flash Flood Statement
National Weather Service Sioux Falls SD
344 AM CDT Fri Jul 3 2026

IAC193-NEC043-SDC127-031030-
/O.CON.KFSD.FF.W.0007.000000T0000Z-260703T1030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Woodbury IA-Dakota NE-Union SD-
344 AM CDT Fri Jul 3 2026

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 530 AM CDT EARLY THIS
MORNING FOR NORTHWESTERN WOODBURY, NORTHEASTERN DAKOTA AND
SOUTHEASTERN UNION COUNTIES...

At 344 AM CDT, Doppler radar and automated rain gauges indicated
thunderstorms producing heavy rain are moving out of the warned area.
Between 1 and 2 inches of rain have fallen. While no additional
rainfall is expected, flooding impacts will continue as water slowly
recedes.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar and automated gauges.

IMPACT...Flash flooding of urban areas, highways, streets and
         underpasses as well as other poor drainage and low-lying
         areas.

Some locations that will experience flash flooding include...
  Sioux City, South Sioux City and North Sioux City.

At 2:20 AM CDT, the public reported water over the curb in 1400 block
of B Street in South Sioux City.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

Please report observed flooding to local emergency services or law
enforcement and request they pass this information to the National
Weather Service when you can do so safely.

&&

LAT...LON 4252 9654 4256 9653 4256 9633 4244 9633
      4243 9641 4245 9645 4248 9643 4247 9649
      4250 9654

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

JH

341 
WGUS73 KFSD 031024
FFSFSD

Flash Flood Statement
National Weather Service Sioux Falls SD
524 AM CDT Fri Jul 3 2026

IAC193-NEC043-SDC127-031034-
/O.EXP.KFSD.FF.W.0007.000000T0000Z-260703T1030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Woodbury IA-Dakota NE-Union SD-
524 AM CDT Fri Jul 3 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 530 AM CDT EARLY THIS MORNING
FOR NORTHWESTERN WOODBURY, NORTHEASTERN DAKOTA AND SOUTHEASTERN UNION
COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a
threat. However, if localized flooding is observed, please report it
to law enforcement. Please do not drive through flooded roads and
heed any road closures.

&&

LAT...LON 4252 9654 4256 9653 4256 9633 4244 9633
      4243 9641 4245 9645 4248 9643 4247 9649
      4250 9654

$$

JH

Area Forecast Discussion
National Weather Service Sioux Falls SD
1244 AM CDT Fri Jul 3 2026

.KEY MESSAGES...

- Thunderstorms will continue along the Missouri River and into
  portions of northwest Iowa into daybreak. 60 mph winds, ping
  pong ball size hail, and torrential rainfall will be the
  greatest risks.

- Extreme uncertainty remains in Friday's forecast. Another
  round of strong to severe storms is possible Friday afternoon
  and night. All hazards may be possible, including strong
  straight line winds in any line of storms that forms.

- With multiple periods of thunderstorms in the region, flooding
  becomes a concern for any locations seeing multiple rounds of
  heavy rainfall. A Flood Watch has been issued for all of
  northwest Iowa into northeast Nebraska through Friday
  morning.

- While severe weather is unlikely on July 4th, isolated to
  scattered showers and storms are possible.

&&

.UPDATE...
Issued at 1237 AM CDT Fri Jul 3 2026

TONIGHT:  Convection continues to develop along periphery of low-lvl
jet convergence near the Missouri River and into the Highway 20
corridor areas. Soundings suggest most of this activity is lifting
off of the 800 mb layer with generalized west to east motion through
the remainder of the night. Strong moisture transport into the
Missouri River valley and Highway 20 corridor, and slow storm motion
AOA 10-15 knots may promote an increased risk for flash flooding
through daybreak. Have expanded the flood watch into NE Nebraska
where recent WOFS guidance indicates 20-30% probabilities for more
than 3" of rain and ensemble max guidance suggesting 5"+ rainfall
amounts could be possible.   Most of this convection will ride along
the edge of the effective shear axis, so while instability of 1500-
2000 MUCAPE will remain, severe risks remain more questionable as
storm clustering and merging may lead to too much competition for
persistent deep and sustained updrafts. Further west, we'll keep an
eye on another wave moving through the western Dakotas, which is
slowly crawling eastward but does have some potential to remain
strong as it reaches the MO river valley. However the atmosphere has
been fairly worked over in the past 12 hours so any additional
development on the 800:700 mb layer may likely stay below severe
limits but should be monitored for lingering gusts.

FRIDAY: The forecast for Friday is, well, very uncertain.  Most CAMs
and other deterministic models have struggled significantly to
resolve even the initialization hours in the past day. That
said, a few different scenarios could play out. The convection
driven by the wave out west may slowly cross the CWA in the
morning, keeping temperatures lower through mid-day and
potentially lowering the severe weather risks. In this scenario
the overnight convection along Highway 20 could also push the
effective front far enough to the south to push
afternoon/evening redevelopment away from us.

Another scenario would be a bit more troublesome if there is less
lingering convection during the morning hours and the effective
boundary to our south isn't driven that far away. Strong diurnal
heating and some early day height rises could push that effective
boundary further north, creating the potential for significant
severe convection to form over the Central Dakotas and then
plunge east southeast as a large MCS. This scenario could bring
another day with all hazards expected, and high end wind gusts.

The end solution might be somewhere in the middle of this, with
morning convection allowing some renewed strong convection by mid-
day, and then we have an earlier than normal severe weather risk,
and perhaps more limited in coverage, through the MO River valley.
Given all this uncertainty, it will be vital to monitor the
conditions through the day.

The forecast for the 4th of July remains favorable and should
remain dry for most of the day. There remains a non-zero chance
for a few late day showers/sprinkles to form and move southeast
in the evening. However wind are very light into the overnight
hours.

&&

.DISCUSSION...
Issued at 245 PM CDT Thu Jul 2 2026

A complex convective evolution is expected for the rest of today,
including the evening and overnight hours, as multiple boundaries
will be in play. An outflow boundary from storms in North Dakota has
pushed into the area near and south of highway-14 corridor early
this afternoon. Thunderstorms, some of which are strong to severe
already, There is also a second boundary near I-90 that served as
the focal point for this mornings storms.

The first round of storms have already fired along the first outflow
boundary from the North Dakota storms. These storms look to affect
locations north of I-90, but especially along and near highway-14.
These storms will be in a favorable environment characterized by
effective shear values up to around 40 knots. Hodographs show a
little curvature in the lowest 0-3 km. But the bulk of the shear
will remain aloft as the right entrance of an upper level jet streak
begins to push off to the northeast. CAPE values will be more than
sufficient with MLCAPE values up to and exceeding 2,500 J/kg. DCAPE
will also be sufficient near to above 1,000 J/kg. Thus, Large hail
up to 2+ inches in diameter and damaging winds to 70 mph will be the
primary hazards. A tornado or two is also possible should a storm
ride along the outflow boundary and efficiently ingest it's
helicity.

This round of storms will be coming to an end by the later evening
hours. However, another shortwave trough will be pushing into the
area, developing a second round of storms along the second boundary.
This second round looks to grow upscale into a mesoscale convective
system (MCS) and push eastwards across locations generally near and
south of I-90. With the upper level jet pushing away from the area,
overall vertical shear profiles will be beginning to weaken.
However, the low level jet will be strengthening which will allow
the MCS to maintain its strength through the overnight hours. Plenty
of elevated instability will be availability in excess of 1,000 to
2,000 J/kg. Vertical shear values will remain sufficient at 40
knots. 0-3 km shear will be a bit on the weak side with magnitudes
up to 20-25 knots. This shear vector may be oriented perpendicularly
off of the MCS which suggests that a tornado threat is possible.
Though this will depend on how the storms and their respective
orientation play out. DCAPE values will remain near 1,000 J/kg but
min to max theta-e difference value's will be low, down to about
-25K. Thus, damaging winds to 75 mph will be the main hazard.

Another round of storms is possible for the day on Friday. With the
previously mentioned shortwave trough east of the area, the daylight
hours for Friday look to be on the drier side due to subsidence on
the backside of the departing wave. Some isolated showers may
persist though. The next chance for strong to severe storms will
come on Friday evening and night. As of now, the latest hi-res
guidance is showing another MCS tracking near to down the Missouri
River Friday night. The environment looks to be more than sufficient
with instability values up to 2,000 to 3,000 J/kg. Effective shear
values up to 40-50 knots will coincide with the larger instability.
0-3 km shear will be stronger at 30-35 knots. Like Friday's storms,
there is some uncertainty regarding the orientation of the 0-3 km
shear vector. If a proper orientation can be achieved, then a line
embedded tornado threat can develop. Min to max theta-e difference
will again be sufficient, down to around -25K. This will support the
potential for damaging wind gusts as the MCS passes through. gusts
may exceed 70 mph. Golf ball size hail could be possible in the
initial developmental stage before a quick transition to a linear
mode occurs. There remains uncertainty regarding the location of
this potential MCS as its overall evolution will be dependent on how
Thursday's storms pan out. Any severe storm threat should be coming
to an end near daybreak Saturday morning. Aside from the severe
storm potential, there remains the potential for flash flooding with
them as well. Please see the hydrology section below for more
information.

Saturday (Independence Day) looks to have some storm potential. An
incoming surface high pressure system looks to push some of the
available moisture to the south of the area. While this does not
mean there will be no instability, it does suggest that the
strongest storms will be off to the south of the as the best frontal
forcing looks to lie near or south of I-80. That said, non-severe
storms are possible which could affect holiday plans. Too early to
say for sure when and where these storms could track. Continue to
monitor the latest forecast for the most up to date information.

The rest of the weekend and first half of next week could feature
additional chances for showers and storms. This potential is
uncertain at this time as the better upper level jet will push away
from the Northern Plains, leaving weaker forcing for this period of
time. As of now, have not strayed the NBM's PoPs at this time.
Otherwise, temperatures look to remain in the 80s to potentially
reaching into the low 90s in a few spots.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1226 AM CDT Fri Jul 3 2026

Conditions near KHON have improved with BKN clouds.
Thunderstorms continue to develop along the Nebraska and South
Dakota border and track slowly eastward. There is a slight
chance these storms move into KFSD bringing higher winds, small
hail, frequent lightning and low visibility. Best chances are in
KSUX where thunderstorms are developing just west of the site.

The main area of storms push into KSUX over the next several
hours bringing low visibility, lightning, potential for hail,
and erratic winds. Conditions start to improve post 12-15z, with
lingering shower chances. Another round of thunderstorms around
the 17z-19z time frame for each of the sites, with clearing near
the 23-02z timeframe.

&&

.HYDROLOGY...
Issued at 245 PM CDT Thu Jul 2 2026

Thunderstorms continue to track along the Missouri River and
into portions of northwest Iowa early this morning. Rainfall
potential of 1-3" with pockets of up to 5" may be possible based
on HREF and WOFS guidance with rainfall rates up to 3-4" per
hour also possible. With this in mind, have extended flood watch
into northeast Nebraska to account for an increased flash flood
risk.

This rainfall, combined with saturated ground from recent
rainfall, may result in enhanced runoff. In addition to flash
flooding, guidance would also suggest some minor to perhaps
moderate river flooding is also possible by this weekend.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...Flood Watch until 7 AM CDT this morning for IAZ001>003-012>014-
     020>022-031-032.
NE...Flood Watch until 7 AM CDT this morning for NEZ013-014.

&&

UPDATE...Dux
DISCUSSION...Meyers
AVIATION...Dux/WFO STO
HYDROLOGY...Dux/Kalin

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
314 AM CDT Thu Jul 2 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-030815-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson-
Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory-
Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook-
Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton-
Union-
314 AM CDT Thu Jul 2 2026

This Hazardous Weather Outlook is for northwest Iowa, west central
Iowa, southwest Minnesota, northeast Nebraska, central South
Dakota, east central South Dakota, south central South Dakota and
southeast South Dakota.

.DAY ONE...Today and tonight.

Scattered thunderstorms will be possible this morning over parts of
northwest Iowa and southwest Minnesota. The main threats will be
quarter sized hail and wind gusts around 50 to 60 mph.

The bigger concern comes this evening into the overnight hours when a
complex of thunderstorms is expected to move into the area from
the northwest. These storms will be capable of producing wind gusts
to 75 mph and heavy rainfall. If a storm can develop this afternoon,
2 inch hail, an isolated tornado and wind gusts to 70 mph are
possible.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Another round of potential severe storms and heavy rainfall will
move into the area on Friday evening and Friday night. Details are
uncertain at this time. It's important to monitor the forecast over
the coming days heading into the holiday weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed.

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
842 PM CDT Thu Jul 2 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0828 PM     Hail             3 NE Emery              43.63N 97.57W
07/02/2026  M1.00 Inch       McCook             SD   Public

&&

JC

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
914 PM CDT Thu Jul 2 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0900 PM     Tstm Wnd Gst     2 NE Rushmore           43.64N 95.77W
07/02/2026  M63 MPH          Nobles             MN   Mesonet

            Mesonet station MN007 I-90 - Rushmore - Mp
            35.

&&

JC