574
FXUS63 KFSD 160344
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1044 PM CDT Sun Jun 15 2025

.KEY MESSAGES...

- Late tonight into Monday morning isolated severe storms will
  be possible in central SD.

- Scattered severe thunderstorms possible Monday afternoon and
  early evening. The cap may hold but if not hail to 2" and wind
  gusts to 70 mph are possible.

- Isolated severe storms possible Monday night into Tuesday
  morning with a potential threat for heavy rain and flash
  flooding in prone areas during this time.

- Very warm temperatures (highs in the 90s) become more likely
  late in the week, with a moderate (40-60+%) probability of
  heat indices topping 100F in some areas Friday and Saturday.
  &&

.DISCUSSION...
Issued at 217 PM CDT Sun Jun 15 2025

A fast moving MCV appears to have driven less unstable air into
southeast SD, and this air continues to push eastward into southwest
MN and northwest IA. This may limit thunderstorm production this
afternoon to area mainly near and east of the Buffalo Ridge south
towards Ida Grove. With CAPE values around 2000 J/kg and weak shear,
locally heavy rain will be the main threat. An isolated stronger
updraft could produce hail to 1.25" to 1.75" and gusts to 60 mph.
This threat would mainly be late afternoon into the early evening.

Upper level energy will work onto the High Plains tonight and could
bring some convective activity into central SD later tonight into
the overnight hours. The better chance will be with the stronger
wave that moves into northern SD late tonight and could drag a
broken line of thunderstorms into areas north of I-90 and likely
near and north of Highway 14. A low chance for severe storms with
quarter sized hail and wind gusts to 60 mph.

On Monday this wave cruises through ND into Northern MN and should
drop a weak front into the area through the day. By late afternoon
this front will likely be near a Windom to Tyndall line and could
spark a few thunderstorms. The latest model guidance is indicating a
bit stronger cap and a bit less instability, albeit still pretty
potent at 2500 to 3000 J/kg. For now the better chance for afternoon
development appears to be in southwest MN closer to the exiting
wave. If storms can develop golf ball sized hail and wind gusts to
70 mph will be possible.

By Monday night the main wave to the north will be well to the
northeast and a weaker wave will move out of Colorado into Nebraska.
With the exiting wave likely leaving behind a low to mid level
boundary, then incoming weaker wave be ignite development along this
boundary, with the3 better chances near and south of I-90 Monday
night into Tuesday morning. While shear continues to be on the
weaker side, CAPE values of 1500-2000 J/kg should provide plenty of
energy to any storms that develop. With a potential west-east
boundary and storm motion likely in an easterly direction, heavy
rain will be a threat. A few locations in far southeast SD and
northwest IA have recently seen 2-5" of rain and will provide some
potential for localized flash flooding. Still a lot to work out
however between now and then so confidence on the low to moderate
side for the severe/flash flooding potential.

This wave moves east on Tuesday and shoves the deeper instability
to the south. However broad troughiness remains in place through
Wednesday so scattered showers and thunderstorms remain possible with
a lower threat for severe.

Thursday into next weekend will see northwest flow aloft give way to
a fairly strong ridge. However, some strong southwest flow aloft
just west of the area by Friday into the weekend could bring a few
surprises and more active weather next weekend if this flow shifts a
bit farther to the east. This will be something to watch. Otherwise,
looking like a fairly hot period Friday into the weekend with highs
in the 90s becoming likely.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1040 PM CDT Sun Jun 15 2025

Chances will be low for thunderstorm activity overnight, though
some guidance would suggest showers and thunderstorms over
western SD moving eastward into the area late tonight. On
Monday, additional thunderstorms may occur in the afternoon and
evening, though confidence in timing and location is low. If
these storms develop, severe storms are likely. Southerly winds
will become gusty on Monday afternoon.

&&

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

&&

$$

DISCUSSION...08
AVIATION...JM