599
FXUS63 KFSD 222256
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
556 PM CDT Thu May 22 2025

.KEY MESSAGES...

- Rain chances increase from west to east on Friday, though the
  eastward extent of precipitation remains uncertain. Thunder
  potential remains low.

- The greatest rainfall amounts will be focused south of the
  James River valley into the Missouri River valley, with mean
  totals between 0.10" and 0.50". Pockets of higher totals
  possible, though uncertain.

- A cool and cloudy holiday weekend is ahead, rain chances
  appear to be focused more in the Missouri River valley than
  elsewhere.

- Temperatures may continue to remain cooler than normal into
  the middle of next week.

&&

.DISCUSSION...
Issued at 226 PM CDT Thu May 22 2025

THIS AFTERNOON:  Partly sunny skies continue as an abundance of CU
remains in the area.  Can`t rule out a very isolated showers into
the evening, but probabilities remain quite low.  Highs are likely
to reach into the upper 50s to lower 60s.

TONIGHT: Winds turn light and variable after sunset, with a clearing
sky this evening.  However after midnight, we`ll begin to see an
increase in mid-upper clouds in response to the arrival of an upper
level jet.  Temperatures by daybreak remain in the lower 40s in most
locations.

FRIDAY:  An upper trough crossing the Upper Rockies will serve to
enhance the return flow through the Plains, while broad isentropic
lift develops showers and isolated thunderstorms by daybreak in the
western Dakotas/Nebraska.  The majority of both CAMs/global models
all support this rain slowly crawling eastward through the day,
though some doubt remains on the overall eastward extend beyond
I-29 given the extensive easterly dry air. Overall instability
remains low, with only isolated chances for lightning in the MO
River valley. QPF is considerably more uncertain. Global models
and their respective ensembles continue to suggest much less QPF
overall than CAMS. In fact the ECE, CME, and GEFS only suggest
low probabilities (<30%) for >0.50" of QPF by Friday night for
a small portion of the MO River Valley. The CAMS all support
much higher QPF totals with 25/75 percentile ranges through the
MO River between 0.40-0.80", and nearly an 80% probability of
>0.50" along and south of the James Rive r. My preference would
be the drier solutions given lack of northward/eastward momentum
in forcing along with influence of lingering dry air. By Friday
evening, soundings do suggest that we may transition towards a
drizzle at times, as mid- lvl dry air arrives and lift focuses
lower into the column.

SATURDAY-MONDAY:  A bit of a chaotic mid-lvl pattern develops
through the upcoming holiday weekend. Medium range models still
struggling to completely resolve the impacts of both long wave
troughing over the Rockies, but also a deepening upper trough over
the Great Lakes. Preference remains that we`ll likely see light
winds, considerable cloudiness, and cooler temperatures Saturday,
with most PoPs focused along or southwest of the Missouri River.
Sunday may feature very similar conditions to Saturday, as a bit
more influence from dry easterly flow arrives. This dry air may keep
any reasonable PoPs along or west of the James River through the
day, with cooler and cloudy conditions further east.

Eventually troughing over the Rockies will begin to slide east,
which most guidance now supports taking place late on Memorial Day.
For the most part, Monday may be again cloudy and relatively cool
for the holiday.

TUESDAY-WEDNESDAY:  Compounding uncertainty completely envelops the
forecast by the middle of next week as extended models and their
respective ensembles bring the Rockies trough eastward and stall it
near the CWA. This would suggest a greater potential for occasional
showers and a continuation of cooler temperatures.  The populated
NBM however is running a bit behind however and temperatures may
trend cooler in upcoming runs.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 552 PM CDT Thu May 22 2025

VFR cumulus currently in place will fade through the sunset
hours giving way to continued VFR conditions and light and
variable winds overnight. At least some signal for patchy fog
along the higher elevation of the Buffalo Ridge/Coteau des
Prairie late tonight but should avoid TAF sites.

Showers will work east/northeast into the James River
Valley/KHON by mid morning Friday and into the I-29
corridor/KFSD/KSUX corridor by midday or early afternoon.
Probabilities favor ceilings remaining in the VFR range although
vsbys may dip into the MVFR range during any heavier showers.

&&

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

&&

$$

DISCUSSION...Dux
AVIATION...Kalin