Lennox, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

661
FXUS63 KFSD 250350
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1050 PM CDT Sun May 24 2026

.KEY MESSAGES...

- Isolated to scattered thunderstorms possible during the late
  afternoon through early overnight hours (5pm-11pm) east of
  Highway 281. Primary risks of 2 inch hail and 65 mph winds.

- Isolated to scattered thunderstorms may redevelop Monday
  evening into Monday night over NW Iowa and NE Nebraska. Non-
  zero severe weather risks may bring gusty winds and hail.

- Temperatures remain 10+ degrees above normal into mid-week,
  but expect a slight cooldown back to normals by next weekend.

- Rain risks return Friday into next weekend (20-40%), however
  severe weather chances are very low.

&&

.UPDATE...
Issued at 1049 PM CDT Sun May 24 2026

With ongoing severe weather across parts of the area, the next
update will out before 5 am on May 25th.

&&

.DISCUSSION...
Issued at 1211 PM CDT Sun May 24 2026

THIS AFTERNOON/EVENING: Temperatures continue to rise towards and
into the 80s this afternoon. Initial mid-lvl vorticity tracking
across South Dakota this morning will keep a narrow channel AC
focused along the Ridge and Minnesota River valley early this
afternoon. Increasing southwesterly surface flow will continue
to pull modest boundary layer moisture northward, but some of
the high-res CAMs are overdoing current moisture at mid-day.
Nevertheless, we should eventually see more consistent
mid/upr-50 dew points arrive by late afternoon. The arrival of
slightly enhanced mid-lvl lapse rates will push MLCAPE values
towards the 1500-2200 J/KG layer by late afternoon. The main
question will then become "where does initiation occur?". Some
preference today for a weak area of surface convergence and low-
lvl jet convergence towards the Highway 14 corridor and into
the Minnesota River valley after 4pm. With inhibition weakened
further south towards the MO River, additional
isolated/scattered development could take place by early evening
further west along a weak dry line near the James River valley,
but this development is much less certain and more conditional
based on weaker convergence. It`s the arrival of mid-lvl
vorticity in the 00-03Z window that may help development further
develop and linger into the early overnight hours before low-
lvl flow veers and pushes convection eastward.

Regarding hazards, the increase in effective shear towards the
30-40 knot mark support a few supercells, with analogs
suggesting 1.5-2" hail potential. A few wind gusts to 60-70 mph
may be possible given steep low-lvl lapse rates, but only
modest DCAPE. The tornado risk remains very low. The west-east
slow storm movement through the Highway 14 corridor this evening
could lead lead to minor flash flood risks with HREF PMM data
suggesting 1-2" per hour rates. Storm risks lower quickly after
midnight with a quiet remaining overnight forecast.

MEMORIAL DAY: Even warmer temperatures are expected for Memorial day
as winds remain southwesterly. Highs are expected to rise into the
upper 80s to lower 90s. One thing to note will be a rise in
afternoon dewpoints towards the lower 60s that may push heat index
values into the 90s. Will also need to monitor the potential for
isolated convection to form Monday evening across portions of north
central/northwestern Iowa into northeastern Nebraska, given the
slightly dirty mid-lvl flow remaining in the Plains. Several CAMS
(more NAM based), all suggest low-end development by late afternoon
to early evening, potentially driven by weak low-lvl convergence on
the developing LLJ. Shear remains rather weak but instability and
mid-lvl lapse rates of more than sufficient. Could see a few
stronger storms with localized downburst winds and severe hail if
trigger mechanism can be determined.  This activity may quickly
weaken after sunset, but continue to drift north into the overnight
hours.

TUESDAY-THURSDAY: The middle of the week favors dry and mild
conditions as a mid-lvl ridge builds through the Plains and extends
northward into Central Canada.  Residing under the ridge of this
quasi-blocking pattern would suggest very weak flow aloft, a slight
influence from east southeasterly surface winds, and dry conditions
with afternoon CU.

FRIDAY-SUNDAY: A broad mid-lvl ridge over the CONUS remains in place
through next weekend.  However, we begin to see eastward shifts in
the the dominant surface high over the Great Lakes, allowing a
better channel of low-lvl moisture to move through the Mid/Upr MO
river valley. What develops is a nearly daily low (20-40%) risk for
shower and thunderstorms, mostly within the peak diurnal timeframe.
Shear and instability in this pattern will be quite weak, so non-
severe thunderstorms are favored.  Temperatures are also favored to
drop closer to seasonal average in the middle to upper 70s.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 634 PM CDT Sun May 24 2026

Showers and thunderstorms have developed across the area late this
afternoon. The storms currently extend along a line approximately
from KMML down through about KAGZ. Some of these storms are produce
large hail and strong winds. These storms will continue to track to
the east and look to make it through the KFSD terminal area. A
little uncertainty remains for KSUX as drier air my prevent storms
from making it KSUX but did include a PROB30 group anyway. Should
see thunderstorms chances wane towards midnight or so. After that,
quiet conditions and southerly winds will persist through the night.

Winds will turn southeasterly for the day tomorrow with gusts up to
20-25 knots. There could be additional storm that develop after the
TAF period ends.

&&

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

&&

$$

UPDATE...05
DISCUSSION...Dux
AVIATION...Meyers