634
FXUS63 KFSD 032313
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
613 PM CDT Wed Jun 3 2026

.KEY MESSAGES...

- Portions of southeast South Dakota will see a Level 2 of 5
  risk for severe storms this evening and again Thursday late
  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.

- Pockets of heavy rainfall in excess of 2 inches are possible
  today through Thursday. Widespread flash flooding risks are
  low. However, flood prone areas and locations which received
  recent heavy rainfall could see isolated impacts.

- 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.

&&

.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 /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 610 PM CDT Wed Jun 3 2026

Scattered convection that forms along and west of the James
River tonight will move eastward later this evening and
overnight. Within this convection risks for larger hail, strong
winds and considerable lightning are anticipated. Brief
reductions to IFR/MVFR visibility and ceilings will be possible,
but impacts at any one location will be short lived. A second
area of convection in Nebraska may struggle to lift northeast,
but will spread a thick mid-upr overcast cloud deck along I-29
this evening.

Latest guidance continues to push this area of convection east
of I-29 by 1am, with lowering ceilings and transition to showers
into daybreak.

VFR conditions likely into Thursday with another widespread CU
field expected.

&&

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

&&

$$

DISCUSSION...AJP
AVIATION...Dux