Flyger, South Dakota Weather Forecast Discussion

435
FXUS63 KFSD 121658
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
1158 AM CDT Fri Sep 12 2025
.KEY MESSAGES...
- Above normal temperatures expected through early next week.
- Rain/storm chances increase this weekend, with a 20-40% chance
  main west of the James River Saturday night and a 40-70%
  chance area-wide Sunday afternoon into Sunday night.
- An isolated severe storm will be possible Sunday into Sunday
  night. Confidence is moderate in this occurring.
- Increasing chance for rain and thunderstorms from Tuesday
  into Wednesday.
&&
.DISCUSSION...
Issued at 320 AM CDT Fri Sep 12 2025
Relatively strong southerly flow at the surface will bring a warm
start to the morning. A weaker wave will move through the area
through the morning into the evening and could bring some spotty
showers and very isolated thunderstorms. While there is some
potential for a few stronger thunderstorms this morning, a low to
mid level dry air will make it almost impossible to tap into that
instability. More than likely any parcel that can lift will be from
above 700 mb and only have 300-500 J/kg CAPE available. Below this
lift will be some very dry air which should limit rainfall potential
at the surface, this feel that we will see isolated to possible
scattered high based ACCAS showers with very isolated thunderstorms.
Otherwise by afternoon there should be a decent amount of sunshine
and with the expected low level temperatures and low level inversion
a hot and humid day is ahead. Highs generally in the mid to upper
80s with dew points in the mid to upper 60s.
The overall support for showers and thunderstorms continues to be
minimal tonight, even with another wave expected to move into
western and central SD. Dry air appears to be too much to overcome.
One exception could be east of I-29 late tonight where some ACCAS
potential exists with very weak instability and decent forcing from
the LLJ. Confidence pretty low on this occurring but will be
something to watch.
Saturday looks to be a very warm and dry day with capping keeping
showers and thunderstorms at bay. South to southwest flow deepens
which should allow slightly better mixing and hotter conditions.
Highs should be into the 90s. Other than a small chance for showers
and thunderstorms in central SD the area should remain dry Saturday
night.
A trough deepens to the northwest Sunday into Sunday night, with a
stronger piece of energy expected to move into the area Sunday
night. Sunday continues to indicate difficulties in any shower and
thunderstorm production, although a few storms will be possible
west of I-29 in the afternoon. By Sunday night cooling aloft and
increased southerly flow in the low levels should bring an increase
in shower and thunderstorm potential. Instability also increases
with CAPE values around 1500 J/kg likely. This should provide enough
energy for isolated severe weather.
As this wave moves northward Sunday night, Monday into Monday night
will likely see mid and upper level ridging which should keep mainly
dry conditions in place. Highs on Monday should be in the 80s.
Tuesday into Wednesday appears to be the areas best chance for a
more widespread rain and thunderstorm potential. Both the GFS and EC
Ensemble indicating a roughly 30-50% chance for a half an inch of
rain or more during this time. As the energy responsible for this
passes, temperatures will settle back to normal or below normal
from mid to late week next week.
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1154 AM CDT Fri Sep 12 2025
VFR conditions continue to move through the region. Mid-lvl wave
moving through will spark scattered showers and thunderstorms
along the Buffalo ridge into early afternoon before shifting
east. Elsewhere, a broken mid-lvl cloud field will develop as
surface winds remain southeasterly.
Tonight will feature VFR conditions once again as winds remain
breezy. Mid-lvl clouds are likely to continue into Saturday
morning. Low probabilities for LLWS develop near Sioux City.
Saturday will feature VFR conditions once again with a gusty
southerly wind developing by mid-late morning.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...08
AVIATION...Dux

NWS FSD Office Area Forecast Discussion