287
FXUS63 KFSD 152317
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
617 PM CDT Tue Jul 15 2025

.KEY MESSAGES...

- Scattered strong to severe storms continue this evening
  mainly across southeast South Dakota and northeast Nebraska,
  with 70 mph winds and ping pong ball- sized hail as the main
  threats.

- Dry and cooler Wednesday and Thursday as high pressure settles
  across the region. Daily highs will top out in the 70s.

- Increasing heat and humidity Friday will allow for a return to
  shower and thunderstorm chances.

- Gradual warming trend this weekend into early next week with
  periodic precipitation chances (20-30 percent).

&&

.DISCUSSION...
Issued at 255 PM CDT Tue Jul 15 2025

TODAY THROUGH TOMORROW: It`s another hot and humid day across the
area, with highs around 90 and dew points around 70. This will help
set the stage for potential severe weather late this afternoon
through tonight as cold front residing just to west of the area will
begin to move through. Initial storm development will likely occur
around the Missouri River Valley in central South Dakota around 21-
22Z and quickly grow into east-southeastward moving linear segments.
The initial development will have 2000-3000 J/kg of MLCAPE and mid-
level lapse rates around 7-7.5 C/km, supporting a threat for large
hail up to ping pong ball in size. The only limiting factor to large
hail development will be modest effective shear of 25-30 kts. As
storms develop into linear segments, expect damaging wind gusts to
take over as the main threat as DCAPE values exceeding 800 J/kg will
exist ahead of the storms. However, the greatest instability will be
pushed south of the area into central Nebraska as the storms move
through, and thus, expect a weakening trend in the storms locally
with eastern extent. Storms will reach the I-29 corridor around
midnight and continue pushing eastward by early tomorrow
morning.

Lows tonight drop into the low-to-mid-60s. With the cold frontal
passage and cloud cover lingering through the day Wednesday, expect
much cooler temperatures for Wednesday afternoon. Highs will range
from the upper-60s to low-70s north to the upper-70s south.
Lingering showers will also be around through Wednesday afternoon.

Thursday will be dominated by surface high pressure region-
wide, resulting in dry conditions and a continuation of cooler
temperatures from Wednesday. High pressure drifts eastward
Thursday night into Friday, allowing for return southerly flow
and increasing temperatures/moisture. Quick-moving minor waves
within quasi-zonal flow aloft will interact with increasing
instability and increase the chances for showers and
thunderstorms, especially Friday night. At this time, 12Z GFS is
very aggressive with mid-level warming, resulting in a stout
thermal cap between 5-10 kft. If this holds, any convective
activity would be elevated. For now, broad brush 20-60 NBM POPs
seem reasonable.

This weekend into early next week, quasi-zonal flow appears to
give way to some synoptic ridging, although the degree to which
this occurs varies widely between medium-range guidance. Overall
impact will be to see gradually rising temperatures each day,
such that a return to the low 90s is possible by Tuesday.
Precipitation wise, weak waves topping the ridge will provide
periodic chances for showers and storms, but lack of continuity
precludes anything more than a 20-30 POP at this time, which is
handled well by NBM guidance.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 612 PM CDT Tue Jul 15 2025

Main aviation concern will be thunderstorms working eastward
through the evening hours. Current indications would suggest
that a weakening trend is expected as these storms approach
KFSD/KSUX but this will continue to be monitored. With the
arrival, and behind the precip, MVFR conditions are expected and
may persist well into Wednesday morning. Winds will also take on
a more northerly direction with some gusts in the 20-25 kt range
(higher in/near thunderstorms).

&&

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

&&

$$

DISCUSSION...Rogers/Samet
AVIATION...Kalin