414
FXUS63 KFSD 041752
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1252 PM CDT Thu Jun 4 2026

.KEY MESSAGES...

- Portions of southeast South Dakota and southwest Minnesota
  will see a level 2 of 5 risk for severe storms late this
  afternoon and evening, with lesser risks farther east and
  south. Large hail and damaging winds are the primary threats,
  with an isolated tornado also possible.

- Some agreement on the better chance for scattered
  thunderstorms containing heavy rain to be generally near
  highway 14 later today into tonight. Confidence is fairly low
  however as there are quite a few differences across many
  models.

- Heavy rain, roughly 2-5 inches, fell across parts of Hamlin
  and Deuel Counties yesterday evening. Will have to see what
  affect this has on the Big Sioux River in Brookings County,
  possibly coupled with additional rainfall today and tonight.

- While details are far more uncertain, an isolated to
  scattered severe storm risk will linger into Friday. The
  greater risks at this time shift southeast into eastern
  Nebraska, Iowa and far southern Minnesota.

- Temperatures remain in the 80s through the week and rise
  towards the low 90s by the end of the weekend.

&&

.UPDATE...
Issued at 258 AM CDT Thu Jun 4 2026

The right entrance region of the upper level jet will exit the area
through the afternoon. This will bring a weak wave to NE into
northwest IA by afternoon and could maintain and area of showers and
thunderstorms through the day over parts of northeast NE and
northwest IA. This will keep showers and thunderstorms over these
areas through the day into tonight. For now these storms should not
be severe or at least any severe weather will be very isolated. To
the north clearing is expected today with instability expected to
build through mid to late afternoon. Still some details to work out
on just where the lower level boundary will be, but a wave is
expected to move into central and northern SD this afternoon and
evening. Ahead of this wave southerly flow will increase a bit, with
the the 925-850 mb warm front expected to set up somewhere close to
highway 14. While deeper layer shear will only be on the weaker
side, roughly 30 knots, CAPE values will climb to 1500-2000 J/kg.
This should support a few strong updrafts with hail to the size of
ping pong balls and wind gusts to 65 mph. However, with freezing
levels about 11.5-12 kft and possible training of cells heavy rain
may become a threat. The latest GEFS and Canadian ensembles are
pointing towards a good chance (30-40 percent) of more than an inch
of rain near and north of highway 14. The 6z HRRR, 0z RRFS and 0z
WRF ARW all point to this location as well with pockets of 2-4", so
will need to keep a close eye on where everything sets up Thursday
afternoon. The KFSD radar indicates a solid core of 3-5" of rain
just north of Brookings county with 1-3" of rain across northern
parts of Brookings county into northern parts of Lincoln and Lyon
counties in MN as well.

&&

.DISCUSSION...
Issued at 304 PM CDT Wed Jun 3 2026

An active few days are in store for the region beginning this
afternoon as an upper trough located over Alberta sends several
waves through the region. Through the day today a deep, warm
layer of moist air will advect into the region from the south.
Highs will climb into the 80s with dew points in the mid 60s.
Plentiful instability (1500-2500+ J/kg) will build into the
region ahead of an approaching cold front. This combined with
steep low and mid-level lapse rates, an increasing LLJ, veering
winds aloft (clockwise hodographs), in addition to strong
divergence aloft set the stage for isolated to scattered strong
to severe supercell thunderstorms to form over central South
Dakota late this afternoon. Low LCL to LFC heights, increasing
helicity and vorticity advection, and favorable shear profiles
(initially perpendicular to the front) indicate that tornados
may be possible with initial supercell formation. One or two of
those tornadoes could be strong, as indicated in the SPC Day 1
Outlook Slight Risk (level 2 of 5). In addition, large hail up
to 2+ inches and damaging wind gusts up to 70 mph are possible.
CAMs guidance varies a bit in timing of initialization, but most
likely it will be between 4-6 pm. Storms will progress eastward
through the evening and overnight. As shear becomes more
parallel to the front, expect that storms will grow upscale into
a quasi-linear system with one or more bowing segments. The
threat will then transition to damaging wind gusts, however a
few brief spin up tornado along the leading edge and hail remain
possible. Timing of storms entering the I-29 corridor region
again varies based on guidance, but in general between 10 pm and
midnight. Storms should then weaken as the move east, exiting
by early to mid-Thursday morning. As far as rain totals go, a
quarter to three quarters of an inch is possible. With a few
isolated areas seeing up to 1+ inches. Widespread flooding is
not expected, but areas that have seen recent rains may
experience isolated flooding.

Thursday will be similar in that another deep layer of moisture
rich, warm air will advect north into the region during the day.
While highs may be limited slightly due to lingering clouds, they
are still expected to reach convective temperatures in the 80s. With
dew points climbing into the upper 60s and low 70s, it will be
another humid day. With the moisture comes renewed instability.
Dynamic parameter`s are all sufficient again for strong to
severe storm development as outlined in SPC Day 2 Slight Risk
(level 2 of 5). The difference Thursday will be that two areas
of development will be possible, and one may impact the other.
The first over northwest Iowa where WAA looks to trigger showers
and thunderstorms in the late afternoon and evening. This
northward push of warm air pushes against a southeastward
advancing cold front, causing it to stall out. As we continue
into the evening, storm initiation will occur as upslope flow
encounters the stalled front. With a similar dynamic setup as
today, strong to severe thunderstorms are once again possible.
Large hail and damaging wind gusts will be the primary threats,
however tornadoes will also be possible at storm initiation.
Overnight storms will grow upscale into a line with wind
becoming the primary threat.

Friday will be another day of increased risk for strong to severe
thunderstorms. However, this round will be highly dependent on how
the previous round played out. Light showers will hang around
through the morning, feeding off remnant outflow boundaries. Friday
afternoon upper ridging to the west and high pressure at the surface
begin to push into the region. This forces the surface low and quasi-
stationary boundary to jump southeast. Timing of this jump will
have a large impact on when and where storm formation will take
place. Current guidance indicates storms are more likely to
form over northwest Iowa, just southeast of the CWA border.
However, there are large differences in guidance, and therefore
certainty in timing is low. Once storms do form, they will have
the potential to be strong to severe as outlined by the SPC Day
3 Slight Risk (level 2 of 5).

Saturday we finally get a break from storms with a dry forecast.
Highs look to climb into the 80s and 90s with slightly breezy
southeast winds. During the day Sunday also looks to be dry with
another day of 80s and 90s and breezy southeast winds. Storm chances
return late Sunday night and continue into the first portion of next
week. However, model divergence increases greatly, keeping
confidence low.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1249 PM CDT Thu Jun 4 2026

Scattered showers and thunderstorms will develop through the
afternoon and especially into the evening and overnight hours. The
best chance of storms will be near Highway 14 west of I-29 into
south-central South Dakota. This puts the greatest confidence for
storms over KHON, especially for the overnight round. Otherwise, low
stratus looks to develop near and east of I-29 tonight into tomorrow
morning where storm chances are the lowest. This will bring mainly
MVFR conditions to those areas, but locally IFR CIGS will be
possible especially over northwest Iowa and far northeast Nebraska.

We`ll see winds increase slightly through the afternoon, sustained
around 5-15 kts, highest in south-central South Dakota. Winds will
become light and variable to calm overnight, and remain on the
lighter side into tomorrow morning. Strong to severe storms will
bring a risk of higher wind gusts, locally as high as 50 kts
through about 05.07Z.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

UPDATE...08
DISCUSSION...AJP
AVIATION...Samet