625
FXUS63 KFSD 240356
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1056 PM CDT Mon Jun 23 2025

.KEY MESSAGES...

- Multiple rounds of showers and storms are expected between
  Tuesday and Thursday which will bring heavy rainfall to the
  region. Amounts up to 2-4 inches is expected at this time with
  locally higher amounts up to 6 inches possible. Training
  storms may result in flash flooding. Rises in rivers and
  streams are also possible in heavier rainfall.

- Isolated strong to severe storms are possible Tuesday and Wednesday
  during the evening and overnight hours. The main threat is
  damaging winds to 60 mph.

- While a brief break in rain is expected for Friday, moderate
  (30- 50%) chances for rain and potential for strong to severe
  storms return for this upcoming weekend.

&&

.DISCUSSION...
Issued at 305 PM CDT Mon Jun 23 2025

A few light showers persist across parts of northwest Iowa this
afternoon. Should see these showers continue to dissipate as the
surface front is situated well south east of the area. While
convection is expected to develop along this boundary, it is too far
southeast of the area to bring any storms to the area. Thus, a quiet
rest of the afternoon is expected. While most of the evening hours
will be quiet, weak warm air advection (WAA) will strengthen aloft
late this evening, allowing for another round of showers and
thunderstorms across far northeast Nebraska and northwest Iowa
tonight. Rainfall amounts will generally be light with most
locations seeing a quarter of an inch or less.

Light rain showers or weak storms pay persist across parts of
northwest Iowa Tuesday morning but should dissipate come the
afternoon hours. 850 mb temperatures will remain in the mid teens
aloft. But with cloud cover hanging around the area throughout the
day, highs will be a bit cooler, only warming to the 70s. Things
begin to change heading into Tuesday evening, beginning the heavy
rain potential across the forecast area. With a Maddox Frontal
pattern in place, the right entrance region of an upper level jet
will provide upper level divergence across the area. Monday`s
boundary will begin to push northwards as a shortwave trough pushes
into the Northern Plains, strengthen low level WAA. Thus, showers
and storms are expected to develop before midnight and last through
the overnight hours. While the surface boundary looks to remain
south of the area, the 925mb front will reside over the area, though
precisely where is still a bit uncertain. Storms will be
encountering a moist environment as the NAEFS ensemble has
precipitable water (PWAT) values reaching up to about the 99.5th
percentile of climatology. CAPE values will be tall and skinny with
magnitudes of 1,000 J/kg or less. Mean flow will not be
perpendicular to the 925 mb front though so storms may not train
over any individual location. However, if storms are able to grow
upscale, then they will follow the corfidi vectors and parallel the
front. Tough to say which solution is the most likely at this time
but believe it will depend on how convection that develops along the
front range of the Rockies grows upscale. Thus, heavy rain will be
the main threat with the storms regardless of convective mode.
Severe weather is also possible given enough shear and instability
will be in place with damaging winds to 60 mph possible.

These showers and storms will last into Wednesday morning before
exiting the area. The surface front looks to finally push into the
area on Wednesday. With WAA continuing aloft, 850 mb temperatures
will warm to the upper teens to low 20s C. This will result in
warmer high temperatures up to the mid 70s to upper 80s from north
to south. Weak capping in place may keep precipitation chances a bit
lower throughout the day. That said, isolated showers and storms
could develop throughout the day with weaker, persistent WAA in
place. The next chance for heavy rain will come Wednesday evening
and night as a similar environment will be in place. Like on
Tuesday, another shortwave trough will push through the area,
igniting this next round of showers and storms. This wave looks to
lead to another round of elevated convection that will sweep across
the area. Isolated severe storms remain possible with this
convection.

This shortwave looks to move a bit more slowly and will persist
through much of the day on Thursday. While lighter showers are
likely, especially during the morning hours, there could be another
round of storms during the afternoon depending on how mesoscale
details shake out. With the shortwave hanging over the area, high
temperatures will be near seasonable with highs in the upper 70s and
80s. The shortwave will finally push east of the area come Thursday
evening, ending the chance for rain across the forecast area.

In terms of rainfall, this event is looking to be a multiple round
event that lasts over the course of 3 days. Though do want to stress
that the bulk of the rainfall looks to fall during the overnight
hours on both Tuesday and Wednesday at this time. The latest
ensemble data is in support of this heavy rainfall as the
distribution of the ensemble clusters data shows a bimodal
distribution. The first peak in the distribution peaks between 2-4
inches while the second peak is highest between 5-6 inches. This
data set is reasonably representative of broad rainfall amounts up
to 2-4 inches with localized higher amounts up to 6 inches depending
on show storms track. Do want to stress that the location and amount
of rainfall can change over the coming day or two as move hi-
resolution guidance becomes available. Please continue to check the
latest forecast for the most up to date information.

The upper level pattern begins to flatten out on Friday, allowing
for dry conditions to return to the region. However, this break in
rainfall may be short lived as medium range guidance is in decent
agreement in a shortwave trough passing through the zonal flow over
the weekend. As of now, the ensembles show a 30-50% chance for
rainfall amounts to exceed a tenth of an inch. With the shortwave in
place, this could lead to severe storms. Something to keep an eye on
over the coming days. Outside of rain and storm chances, highs look
to return back to the 80s and potential the 90s for the end of the
week.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1051 PM CDT Mon Jun 23 2025

MVFR ceilings are lifting from southern Nebraska and southern Iowa
into our area, and will bring impacts to airports along and south of
a KYKN to KSPW line through the rest of the night into Tuesday
morning. There will also be scattered showers and thundershowers in
these areas through Tuesday morning. These showers will try to make
a push towards I-90, and thus added VCSH to KFSD to account for
this. MVFR CIGS will return to the area from roughly south to north
Tuesday evening as additional showers and storms move into the area.

Winds will be mainly light tonight and into Tuesday morning. Winds
will gust up to 15-20 kts in the afternoon, strongest in and around
K9V9. Winds will gradually turn from the northeast to the
east/southeast gradually throughout the period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Samet