Davis, South Dakota Weather Forecast Discussion

466
FXUS63 KFSD 161130
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
630 AM CDT Tue Sep 16 2025
.KEY MESSAGES...
- Tuesday will again be warm with highs in the mid-to-upper-80s,
  with some spots possibly reaching 90 mainly east of I-29.
  Temperatures cool off to end the work week.
- Scattered showers and thunderstorms return from late Tuesday afternoon
  onwards. While half dollar-sized hail and damaging wind gusts
  up to 65 mph will be the main hazards with any stronger
  activity, pockets of locally heavy rainfall are likely.
- Additional chances for showers and thunderstorms continue from
  midweek into the start of the weekend. While the overall
  severe threat will be low, pockets of locally heavy rainfall
  will be possible.
&&
.DISCUSSION...
Issued at 343 AM CDT Tue Sep 16 2025
We`re starting this morning with mainly clear skies across the
area. Another unseasonably warm day is in store for our day
today, with highs well into the 80s with the potential for some
places to reach 90 especially east of I-29. Showers and storms
have been ongoing this past night west of the area in western
South Dakota and the Nebraska panhandle, which are slowly
pushing eastward while weakening as it moves away from the
upper-level support. Can`t rule out a shower or two lasting into
areas west of the James River around sunrise, but any activity
would be light or may not even make it to the ground at all due
to the amount of dry air the raindrops would fall into. The main
story today will be the increasing storm chances this afternoon
and evening as daytime heating destabilizes the atmosphere and
leads to around 1500-3000 J/kg of MLCAPE to develop through the
day. A developing upper-level low over the northern Rockies will
slowly push eastward and start to nudge a frontal boundary into
our area and this will be the focus for storm development
through this evening. Soundings indicate the cap weakening and
breaking in the early to mid-afternoon west of the James River
just ahead of the front, which could lead to isolated to
scattered thunderstorm development. Lapse rates will be around
7-7.5 C/km, but bulk shear will be quite weak (less than 10 kts)
during the afternoon, so storms may struggle to become severe.
If an updraft can sustain itself, then hail up to the size of
half dollar coins will be possible. Dry mid-level air will also
lead to a damaging wind threat, with gusts up to 65 mph
possible.
Additional showers and isolated severe storms may develop farther
east into the evening as the frontal boundary drifts eastward, but
showers and storms will increase in coverage tomorrow morning as the
upper-wave and large-scale ascent spreads into our area. Latest
guidance has backed off the timing of this main wave to later than
previously expected, but still expect a 60-80% chance of rain
through the day Wednesday into Wednesday night as the upper-low
meanders around the area. It won`t be raining all day long, but
tall, skinny CAPE profiles will lead to locally heavy rainfall from
time to time, which could cause minor urban and low-lying area
flooding. For that reason, there is a Marginal Risk (Level 1 of 4)
for flooding from the Weather Prediction Center. Severe weather is
not expected tomorrow, though a stronger storm with gusts up to 50
mph and small hail can`t be ruled out mainly over northwest Iowa
where instability will be a bit higher than compared to the rest of
the area. Most of the area will see around a half an inch of rain
Wednesday into Wednesday night, though some locally higher amounts
up to an inch or so appear likely in spots. Temperatures will be
cooler on Wednesday due to the frontal boundary clearing the area,
with highs mainly in the 70s with the exception for areas east of I-
29 where we may see some highs into the low-80s.
The upper-low will continue to hang around into the day on Thursday,
keeping us wet, cloudy, and with near to slightly below seasonal
normal temperatures. In terms of rainfall amounts, ensembles are
showing of a 20-40% chance of at least a half an inch of rain
Thursday into Thursday night. A trough coming out of southern Canada
on Friday may finally provide the kick to start moving the upper-low
out of our area, but not before rain chances continue for Friday and
even into Saturday (mainly east of I-29 by Saturday). Models diverge
significantly from there, but as rain chances wind down to end the
weekend, expect another warm-up into next week.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 629 AM CDT Tue Sep 16 2025
VFR conditions are expected for the daytime hours, with only a low-
end chance of fog development through 13z. Although a brief
drop to 5SM visibility can`t be entirely ruled out if fog
develops (like seen thus far at KVMR and KLYV), kept VFR
conditions in the TEMPO group for KFSD and KSUX. Scattered
showers and storms are set to develop late this afternoon into
the evening hours, but for the most part should stay west of the
TAF sites as guidance keeps coming in later and later for the
timing of the more widespread TSRA/SHRA activity to move in.
Still, enough confidence for a PROB30 group this evening for
KHON and PROB30`s for KFSD and KSUX for the last few hours of
the period.
Winds will be fairly light throughout the period, around 5-10 kts.
Variable wind direction is expected in the KHON-area through the day
as a rather diffuse frontal system drifts slowly across the
area. Winds should be mainly out of the south/southwest
elsewhere, turning light and variable area-wide tonight.
Stronger wind gusts are likely if a storm develops, with winds
up to 35-40 kts though an isolated 50+kt gust can`t entirely be
ruled out in the strongest storms mainly west of I-29 this
afternoon and evening.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...Samet
AVIATION...Samet

NWS FSD Office Area Forecast Discussion