011
FXUS63 KFSD 022304
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
604 PM CDT Wed Jul 2 2025

.KEY MESSAGES...

- Additional isolated storms are possible this evening and
  night, mainly along and east of I-29. Isolated strong to
  severe storms are possible with large hail up to the size of a
  quarter (1 inch) and damaging winds to 60 mph.

- Chances for showers and storms will continue for Independence
  Day through the holiday weekend. Currently, highest chances
  (45-70%) are on Friday afternoon into Saturday. Severe weather
  risk remains low but confidence is beginning to increase in
  this potential. Locally heavy rain is also possible with the
  storms. Keep an eye on the forecast if you have outdoor or
  travel plans.

- Temperatures generally near to above normal through the next
  week. Thursday Friday could see heat index values into the 90s
  and approach 100 degrees.

&&

.DISCUSSION...
Issued at 300 PM CDT Wed Jul 2 2025

Quiet conditions persist through the first half of the afternoon
hours. However, there looks be some weak showers that develop this
evening and night along and east of I-29 as a weak theta-e boundary
pushes into the area. Lifting from this boundary will be quite high,
above 850mb which will result in limited instability to work with.
That said, still enough instability for thunderstorms to develop
along with effective shear values up to around 30 knots. Thus, an
isolated severe storm with large hail up to the size of a quarter
and damaging winds to 60 mph is possible. Low temperatures will fall
to the 60s overnight.

An upper level ridge axis will sit over the region on Thursday. This
will push the best forcing for ascent away from the forecast area
and result in dry conditions for the day. Beneath the ridge, warm
air advection (WAA) will push 850 mb temperatures up to the upper
teens to mid 20s aloft. Mixing these temperatures to the surface
will result in hot high temperatures up to the upper 80s to about
100F. Heat indices will also be hot in the 90s to just touching
100F. At the surface, the surface pressure gradient will tighten,
leading to breezy southerly winds. This may bring the feeling of the
heat and humidity down just a bit but regardless, Thursday will be a
hot and humid day. Those with outdoor plans will want to drink
plenty of water, even if outdoor activities take place after work.
The hot and humid conditions will not wear off overnight though as
persistent southerly flow will keep lows above average in the 70s
across the area.

Heights begin to fall aloft on Friday as the previously mentioned
ridge axis slides east of the area. Medium range guidance continues
to come into better agreement in a shortwave trough pushing into the
Northern Plains. This wave will strengthen warm air advection (WAA)
across the area, keeping 850 mb temperatures in the low 20s. Mixing
these temperatures to the surface will yield another day with highs
in the upper 80s and 90s. With highs just a touch cooler then
Thursday`s highs, heat indices will also be a bit cooler in the
upper 80s and 90s. Starting to see a few hi-res models come in for
Friday afternoon and continue to support the notion of scattered
showers and thunderstorms developing in an uncapped atmosphere. As
of this latest data, looks like the showers and storms will
initially develop along a surface boundary west of the James River
and the push eastwards through the rest of the afternoon and evening
hours. Late Friday afternoon, evening, and overnight still have the
highest probabilities for rain, remaining at a 45-70% chance. The
wave responsible for the showers and storms will be quite weak
though. With a weak wave in place, shear will be weak. Mid level
lapse rates will be closer to moist neutral but low level lapse
rates will be steep enough to generate sufficient instability on the
order of 1,500 to 2,000 J/kg of CAPE. At the same time, warm cloud
depths will span to up to around 13,000ft while precipitable water
(PWAT) values place in the 97.5th percentile of climatology per the
NAEFS ensemble. Thus, locally heavy rainfall is possible with the
storms, especially if they track over the same location. With a
moderate CAPE/low shear set up, severe weather chances remain low.
At this time, it looks as if damaging winds will be the primary
hazard given DCAPE values between 800 to 1,000 J/kg.

Chances for rain (30-60%) persist into Saturday as the shortwave
will be a bit slow to exit the area. Diurnally driven showers and
storms will again result in the highest chances for rain coming
during the afternoon hours. High temperatures will be a bit cooler,
only warming to the 80s across the area. Lows will be near average
in the 60s. The wave finally pushes east of the area on Sunday,
delivering a break from the showers and storms.

This break will be short lived though as zonal flow sets up for the
first half of next week. Shortwaves within the zonal flow will bring
renewed chances for showers and storms but medium range guidance
show large variance in these shortwaves. Thus, have left model
blended PoPs in place. Aside from rain chances, highs will remain in
the 80s and 90s.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 558 PM CDT Wed Jul 2 2025

VFR conditions expected through the period. Isolated showers
and storms are possible through about 08Z tonight mainly into
portions of southwestern Minnesota and northwest Iowa east of
KSUX. Impacts to TAF sites are unlikely (<10% chance of rain).

Winds will be light tonight and out of the east-southeast. Winds
will turn more southerly Thursday afternoon, with gusts increasing
to 15-20 kts for the area east of the James River. Winds west of the
river could gust as high as 25 kts at times tomorrow afternoon.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Samet