521
FXUS63 KFSD 012311
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
611 PM CDT Tue Jul 1 2025

.KEY MESSAGES...

- Scattered showers and storms will develop late tonight and
  persist through Wednesday morning. 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
  (45-75%) are on Friday afternoon into early Saturday. Severe
  weather is currently not expected, but locally heavy rain is
  possible. Keep an eye on the forecast if you have outdoor or
  travel plans.

- Temperatures generally near to above normal through the next
  week. Wednesday through Friday could see heat index values
  approach 100 degrees.

&&

.DISCUSSION...
Issued at 302 PM CDT Tue Jul 1 2025

Mainly quiet conditions persist this afternoon as high pressure is
pushing out of the area, setting up southerly return flow in its
wake. Although a light breeze, should still make for pleasant outdoor
conditions this evening. Things begin to change heading into the
later evening and overnight hours as a weak ridge riding shortwave
trough pushes into the forecast area from the northwest. This wave
will strengthen the low level jet (LLJ) and increase warm air
advection (WAA) across the area. With the nose of the LLJ over the
forecast area, convection looks to develop along the 750mb front
around to just after midnight across central South Dakota, near to
east of the Missouri River. The storms will track southeastwards
through the rest of the overnight hours. Modest elevated instability
will be in place with CAPE values on the order of 1,000 to 1,500
J/kg and effective shear values of 30-40 knots will make for an
environment favorable for isolated strong to severe storms. Latest
hi-res guidance is in agreement on a cluster of storms developing on
the nose of the LLJ. Given the close proximity of storms, think
that colliding storms should keep the hail threat contained to
quarter size hail (1 inch in diameter). Although storms will be
elevated, downdraft convective inhibition (DCIN) is 0, suggesting
that damaging winds will have an easier time being brought to the
surface. Thus, damaging winds to 60 mph is also on the table for
tonight. The storms will track southeastwards through the area for
the rest of the overnight hours and into the early morning hours
tomorrow. Low temperatures will only fall to the low to mid 60s
overnight.

Remaining showers and storms will push through the area through the
rest of the morning hours on Wednesday. While most of the afternoon
hours will be dry, persistent weak WAA could lead to isolated
showers and storms redeveloping, mainly east of I-29. Aside from
rain chances, highs look to be a warmer in the mid 80s to upper 90s.
The warmest temperatures will occur west of the James River. Heat
indices in the 90s to approaching 100F is expected along and west of
a De Smet, South Dakota, to Luverne, Minnesota, to Spencer, Iowa
line. Low temperatures will fall to the 60s overnight.

A break in rain chances will come on Thursday as the axis of an
upper level ridge pushes through the Northern Plains. 850 mb
temperatures will warm to the low to mid 20s aloft, resulting in
high temperatures in the upper 80s to upper 90s. Locations west of
the James River may even approach 100F. Heat indices will also be in
the 90s to near 100F, making for a hot and humid day across the
area. The surface pressure gradient will tighten across the forecast
area, leading to breezy southerly winds. Despite the heat and
humidity, the breezy winds should make outdoor conditions feel a bit
cooler. Low temperatures will be very mild overnight, only falling
to the 70s, thanks to the persistent southerly winds.

Heights begin to fall aloft on Friday as the previously mentioned
ridge axis slides east of the area. High temperatures will remain
warm though a bit cooler than Thursday with highs in the upper 80s
to mid 90s. Heat indices will again be in the 90s though should
remain just below 100F. A shortwave trough will push into the
Northern Plains on Friday bringing renewed rain chances with it. The
quasi-geostrophic forcing from this wave looks to result in
scattered showers and thunderstorms across the area for late Friday
afternoon and evening given that the atmosphere will be uncapped.
The evening and overnight hours will have the highest chances for
rain, up to a 45-75% chance. Given the weak strength of the wave,
little to any shear will be in place. Thus, the chance for strong to
severe storms is low (<20%). At the same time, precipitable water
(PWAT) values will climb up to about the 99th percentile along with
integrated vapor transport values pushing into the 90th percentile
of climatology per the NAEFS ensemble. BUFKIT soundings show a deep
warm cloud layer with a depth up to 12,000 to 13,000ft. Any storm
that develops may be capable of heavy rainfall, especially if storms
train or sit over any individual location.

The same shortwave trough will continue to slowly push through the
area through the day on Saturday. This will keep chances (30-60%)
for rain in the forecast until the wave finally pulls away on
Sunday. Temperatures over the weekend will be slowly cooling, down
to the 80s on Saturday and upper 70s and 80s on Sunday.

A zonal pattern sets up for early next week which could bring
additional chances for rain with it. However, this potential is
uncertain given how it looks to be dependent on weak shortwaves
tracking through the zonal flow. Medium range guidance shows a large
variance in these waves so have left model blended PoPs in place.
Aside from rain chances, highs look to remain in the 80s Monday and
Tuesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 608 PM CDT Tue Jul 1 2025

Scattered showers and thunderstorms will be possible later
tonight into Wednesday morning, then again on Wednesday
afternoon. The better chances will be near and north of I-90
tonight into Wednesday morning, with the better chances in
northwest IA Wednesday afternoon. A few stronger storms will be
possible with hail up to quarter size and wind gusts up to 60
mph possible.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...08