South Sioux City, Nebraska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

280
FXUS63 KFSD 051146
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
646 AM CDT Sat Jul 5 2025

.KEY MESSAGES...

- Scattered showers/storms will linger through today, mainly near
  and east of I-29. The risk for severe weather is low; however,
  may have to watch for weak funnels with developing showers this
  afternoon.

- Additional showers/storms are possible Sunday (west of James
  River Valley) and Monday night-Tuesday. Some stronger storms are
  possible, but details are uncertain.

&&

.DISCUSSION...
Issued at 325 AM CDT Sat Jul 5 2025

REST OF THE HOLIDAY WEEKEND: A mid-level trough over the area
early this morning will slide east toward the western Great Lakes
through the day. Various waves moving through the trough will
produce scattered to numerous showers and embedded thunderstorms
today. The lead wave which continues to drive precipitation over
mainly northwest Iowa/southwest Minnesota as of 3 AM will move
east of the area by shortly after sunrise, which should bring a
decrease in activity through the morning. However, a trailing wave
dropping south into the back side of the departing trough should
support additional showers and scattered storms this afternoon.
This activity looks to impact areas mainly along/east of I-29,
though a few solutions do pull the rain chances a bit farther
west, so will have to monitor trends.

A weak boundary currently poised just northwest of our forecast
area will accompany this trailing wave and could be a focus for
development this afternoon. Although instability is decent with
MLCAPE 1000-1500J/kg, deep layer shear is once again quite weak at
<20kt. DCAPE is also weak at <500 J/kg most areas (pockets of
higher amounts), so am not expecting severe storms to develop this
afternoon. However, the weak shear and presence of the boundary
in a well-mixed boundary layer could support development of weak
funnels in the developing stage of showers/storms, as indicated
by areas of NST (Non-Supercell Tornado parameter) > 1. Although
these types of funnels are usually short lived and weak, and
usually will not touch the ground or cause damage, those with
outdoor plans should keep an eye to the sky and seek shelter if
you feel your safety is threatened.

This activity should wane quickly after sunset with loss of
heating, leaving a mostly dry night ahead. However, we will be
watching additional storms over the High Plains to our west which
could brush our far western counties early Sunday. Another weak
mid-upper level wave could also spark some showers/storms west of
I-29 Sunday afternoon-night, though confidence in this activity
is currently low given difference in timing/strength of the wave
in the models.

As far as temperatures this weekend, we should see readings much
closer to, or even a bit below normal for the first week of July.
Highs today and Sunday are expected to be in the upper 70s to mid
80s. Humidity will remain uncomfortable with dew points still in
the 70s ahead of the boundary today, but this front will usher in
lower dew points in the mid 50s to mid 60s tonight into Sunday.

MONDAY-TUESDAY: Quasi-zonal flow will dominate the first part of
the upcoming week with subtle waves keeping low chances for
showers and storms across the area Monday into Tuesday. An
increase in mid level flow will boost deep layer shear in an
unstable environment, so some strong to severe storms appear
possible later Monday into Monday night, as highlighted by a
broad Marginal (Level 1 of 5) Risk in SPC`s Day 3 outlook.

WEDNESDAY-FRIDAY: Details are a little more murky regarding the
evolution of the upper level flow pattern late week. However,
broad consensus shows a weak upper level ridge briefly builds over
the Rockies/High Plains mid-week before quickly flattening back
into a broad westerly flow Thursday-Friday in response to a
stronger northern stream trough moving across Canada. This will
keep us in an unsettled weather pattern for the latter half of
next week with periodic chances for showers/storms. Similar to
Monday-Tuesday, details are uncertain. However, machine learning
probabilities highlight a potential for some strong to severe
storms during this period. The mid-week ridging could support
highs in the 90s working back into our western areas Wednesday
into perhaps Thursday, followed by cooling again heading into the
weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 645 AM CDT Sat Jul 5 2025

Overnight rain/isolated thunderstorms have been slowly slipping
eastward across northwest Iowa early this morning. This activity
will continue to push slowly east through mid-morning, with
areas of MVFR-locally IFR ceilings slower to improve/lift into
lower VFR range.

Additional showers/storms are expected to develop during the
afternoon, especially along and east of the I-29 corridor. MVFR
ceilings and brief MVFR visibility may accompany precipitation,
but otherwise VFR conditions are expected to prevail through the
remainder of the period.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...JH