Sioux City, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

614
FXUS63 KFSD 141710
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1210 PM CDT Wed May 14 2025

.KEY MESSAGES...

- The chances for showers and thunderstorms will increase after
  6pm initially across southcentral SD then gradually spread
  northeastwards overnight. Large hail (1.5") and damaging wind
  gusts up to 65 mph will be primary threats with stronger
  storms along with locally heavy downpours.

- Lingering showers could persist mostly north of I-90 during
  the day on Thursday.

- Near to just below normal temperatures will persist into the
  new week.

&&

.DISCUSSION...
Issued at 400 AM CDT Wed May 14 2025

TODAY-THURSDAY: More warm and dry conditions ahead! Taking a look
across the area, another warm start will be in store as most areas
wake up to temperatures in the upper 50s to low 60s this morning.
With southeasterly surface winds and increasing mixing in place,
expect temperatures to warm in a hurry eventually peaking the upper
80s to low 90s by this afternoon. From here, our attention turns
towards the Rockies as a deepening upper-level trough ejects into
the plains bringing renewed chances for showers and thunderstorms.
Initial thunderstorm develop will be tied to a slow-moving cold
front which will sit over central SD and northcentral NE for much of
the afternoon. However, we`ll start to see this developing activity
push into portions of southcentral SD and the Missouri River Valley
between 5-7 pm this evening as the previously mentioned system
progresses eastwards with time.

Looking at the environment ahead of the front, long skinny cape
values between 1500-1800 J/kg and decent mid-lapse rates between 6.5-
7.0 degrees C/kg will be favorable for some marginally severe hail
up to ping pong ball size (1.5") with stronger updrafts. However,
with meager shear values of 15-25 kts; will likely start to see
developing storms begin to collapse on themselves becoming more
outflow dominant (DCAPE=1200) as cold pools form. With this in mind,
could see damaging wind gusts up to 65 mph underneath any dying
thunderstorms. Lastly, with the mean wind expected to parallel to
the cold front and PWATs approaching 1-1.5 inches according to the
ESAT tables; developing showers and thunderstorms could "train" over
portions of southcentral SD leading to not only some beneficial
rainfall, but also some localized ponding. Nonetheless, with those
areas sitting in a D1-D2 drought; any flooding concerns should be
kept to a minimal. From here, we`ll start to see the environment
change during the early hours of Thursday as the now negatively
tilted trough begins to wrap up forming an upper-level low (ULL).
Any developing convection will be now meet with a nocturnal LLJ (45-
55 kt) as things continue to track northeastwards along and east of
I-29 overnight.

With the increase in shear, lapse rates will steepen leading to the
potential for larger hail stone of golf ball size (1.75") or larger.
Could also see an increase in the damaging wind threat as a few
bowing segments form. However, the faster storm motions should help
most of the stronger activity push out of our area by daybreak
Thursday. Looking into the rest of Thursday, the dreary will likely
persist for the rest of the day as the ULL moves through the area
during the first half of the day. The combination of synoptic lift
associated with the ULL and a strong LLJ will lead to additional
showers and thunderstorms development especially along and north of
I-90 through the early afternoon. With this in mind, could see an
additional 0.25-0.75" of an inch in the areas outlined. Lastly,
variable surface winds will become gusty westerly winds by Thursday
afternoon as the surface low lifts northwards. With soundings
continue to hint at 45-55 kts at the top of the mixed layer for some
spots; we`ll definitely have to monitor for a potential wind
headline Thursday afternoon.

THE WEEKEND ONWARDS: Heading into the weekend, multiple pushes of
cold air advection (CAA) behind the previously mentioned system will
help keep temperatures near to just below our seasonal normals as
highs top out in the upper 50s to upper 60s across the area. Upper
level ridging will build in over the weekend to keep things dry over
the weekend. However, with a tightening SPG in place; periodic
breeziness is expected through Saturday with the strongest winds
occurring on Friday. Our next rain chances will likely occur on
Monday as another deepening trough lifts out of the Four Corners
region. However, with slight amplitude and timing differences among
long-range guidance; its too early to iron out the finer details.
Nonetheless, with ensemble guidance showing 60-80% chances for at
least 0.25" of an inch of liquid across the area this will likely be
a system to monitor moving forward.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1208 PM CDT Wed May 14 2025

VFR conditions continue into the early evening as breezy
southwesterly winds persist.

We`ll be watching convection form along a front in central SD/NE
later this evening. This convection will track northeast late in
the evening but more likely overnight. While some weakening may
take place as it arrives near I-29 early in the morning, brief
pockets of 50+ mph winds may be possible. Ceilings and
visibility in convection may fall below VFR levels at times.

The initial wave of convection moves through, but additional
rounds of showers and thunderstorms will be possible through the
morning. Winds are expected to turn quite gusty from the west by
mid-late morning.


&&

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

&&

$$

DISCUSSION...05
AVIATION...Dux