Chester, South Dakota Weather Forecast Discussion

818
FXUS63 KFSD 261132
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
632 AM CDT Fri Sep 26 2025
.KEY MESSAGES...
- Aside from a brief cooldown Saturday, the week ahead will be
  dominated by well above normal temperatures for late September
  to early October.
- Dry conditions will continue through the middle of next week,
  with low precipitation chances returning by Thursday-Friday.
- Occasional breezy afternoons and drying grasses may lead to
  localized elevated fire weather concerns, mainly toward
  south-central South Dakota today and early next week.
&&
.DISCUSSION...
Issued at 325 AM CDT Fri Sep 26 2025
A low level thermal ridge builds across our western counties
today ahead of an approaching cool front. A dry atmosphere will
promote efficient mixing, a scenario which supports nudging our
dew point/winds a little drier/higher than the NBM. As far as
temperatures, warmer is also favored, but the NBM already falls
between its 75th and 90th percentile values, so minimal changes
to the NBM in the temperature department. As temperatures climb
into the 80s (warmest near/west of the James River), afternoon
humidity levels dip to around 30%, with occasional gusts topping
25 mph toward south-central South Dakota. We are early enough
in the fall fire weather season that grasses still have some
greenness and as such, do not expect to reach critical fire
weather conditions. However, satellite NDVI/greenness estimates
indicate grasses are starting to cure, especially over portions
of south-central and southeast SD where rainfall has been more
sparse over the past few weeks. So localized areas with drier
grasses may see elevated fire weather concerns.
The aforementioned cool front swings through the area tonight
as its associated wave slides east well to our north. With
minimal moisture, expect only a wind shift and perhaps a slight
increase in clouds to mark its passage. Temperatures cool into
the 70s for highs behind the front Saturday, which is still
above normal for late September. This relative cool-down will be
short-lived, though, as a stronger mid-upper level ridge builds
back into the Upper Midwest (far eastern Dakotas/Minnesota/Iowa
and into the western Great Lakes) early next week. NAEFS/ECMWF
ensembles show 700-500MB heights and corresponding 850MB temps
above the 90th percentile for late September on Sunday-Monday
(maximized across Minnesota), which will result in a quick
return to well above normal highs in the 80s.
The ridge remains dominant across the western Great Lakes into
at least the middle of next week while a closed mid-upper level
low develops near/off the Pacific Northwest coast. While a few
waves slide north-northeast across the northern Plains between
these two features, moisture remains lacking across our forecast
area through at least Wednesday, keeping precipitation chances
non-mentionable. This may change by late next week as the upper
trough slides east into the Canadian Prairies, but differences
in the evolution of this trough leads to low confidence in
precipitation chances.
As far as fire weather concerns, Sunday/Monday could bring some
stronger southerly breezes to areas west of I-29, and localized
areas with drier fuels may again have to watch for elevated
fire danger. However the persistent southerly flow may also draw
higher boundary layer moisture northward, keeping afternoon
humidity levels more in the 30-40% range.
&&
.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 630 AM CDT Fri Sep 26 2025
Shallow early morning fog may produce very localized MVFR-IFR
visibility, though potential at TAF sites is too low to include
in this TAF issuance.
Breezy southerly winds develop this afternoon with gusts 20-25kt
along and especially west of I-29. Gusts diminish with sunset,
but a passing cool front could bring a period of northwesterly
gusts at or above 20kt during the nighttime hours.
VFR conditions will prevail through the period.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...JH
AVIATION...JH

NWS FSD Office Area Forecast Discussion