311
FXUS63 KFSD 031126
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
626 AM CDT Thu Jul 3 2025

.KEY MESSAGES...

- Isolated storms continue through mid morning. A storm could be
  severe with hail to half dollar sized and wind gusts to 60
  mph.

- After morning storms, most of today remains dry but hot and
  humid. Heat index values in the upper 90s to near 100 today.
  Hot and humid Independence Day with heat index values in the
  mid 90s to near 100.

- Chances for showers and storms continue Independence Day
  through the holiday weekend. Highest chances (45-70%) begin
  Friday afternoon into Saturday evening. Periodic shower and
  storm chances continue into next week.

- Severe weather risk remains low but not zero for Independence
  Day and Saturday. Locally heavy rain is also possible. Keep
  an eye on the forecast if you have outdoor or travel plans.

- Temperatures generally near to above normal through mid next
  week.

&&

.DISCUSSION...
Issued at 354 AM CDT Thu Jul 3 2025

THROUGH TONIGHT: Isolated thunderstorms near the I-29 corridor south
of I-90 continue to slide east this morning with WAA and the nose of
the LLJ. Have seen a couple storms pulse up overnight with one
producing half dollar sized hail (1.25" diameter). Believe these
storms are remaining elevated given surface capping based on the
sounding data. Elevated instability around 1500 J/kg with lapse
rates around 6.5 deg C/km and shear around 30 knots maintains a low
end, isolated severe weather risk through the mid morning before
storms exit the area. Main threats are hail to half dollar sized and
wind gust to 60 mph if a storm pulses up.

Ridge axis aloft slides overhead today. Increasing southerly surface
flow and WAA aids in warming temperatures above average and
increases humidity. Highs in the 90s with heat index values in the
upper 90s to near 100 as well. A few areas approach/exceed Heat
Advisory criteria for a brief time, but held off on a headline given
uncertainty of dew points - especially if mixing is more efficient.
Will allow day shift to monitor and issue if needed.

By tonight, attention turns to the lee side surface low pressure
moving into the western Dakotas and mid/upper level wave deepening
over eastern WY which will move east through the holiday. Lows
tonight remain on the warm side with breezy southerly winds and
humid conditions. Lows in the 70s.

JULY 4TH-SATURDAY: Low pressure strengthens over the Dakotas July
4th, sliding east through the day and into the night. This drags a
cold front to the east, into south central SD into northeastern SD
by the evening hours in tandem with a mid level wave. Storms should
begin to fire in the late afternoon and early evening with diurnal
heating and essentially no cap in place. Instability generally
around 1700 J/kg near/just ahead of the front. Shear values are low,
with most guidance indicating bulk shear near 25 knots. Mid level
lapse rates are meager, around 6 deg C/km or less. Isolated strong
to severe storms are possible after 5 PM on Independence Day,
continuing through the evening hours and into the night as the
storms move east. Storms should quickly grow upscale and into a line
with shear vectors nearly parallel to the front. Main threat with
storms will be wind gusts of 60 mph with DCAPE values around or
above 700 J/kg. First area of storms should exit the area by early
Saturday morning. However, another mid level wave and surface
boundary over the area lead to continued, mainly diurnal, showers
and storms on Saturday into Saturday night. Severe risk is low on
Saturday. Storms this weekend may produce locally heavy rainfall.
PWAT values remain in the top 1% when compared to climatology. Deep
warm cloud layers over 12kft and efficient low level moisture
transport support heavier rainfall rates.

Heat index values on July 4th remain in the 90s to near 100 with
temperatures in the upper 80s to mid 90s and dew points in the upper
60s to mid 70s. Saturday looks a touch cooler with lingering showers
and storms; highs in the 80s.

SUNDAY: Wave departs the area Sunday, with weak surface high
pressure building in. Cooler with highs in the upper 70s to mid 80s
and mostly dry conditions. Flow aloft begins to shift more zonal
into Sunday night.

MONDAY-MID NEXT WEEK: Surface high pressure slides east Monday.
Zonal flow continues through early next week with continued weak
waves through the pattern. Northwesterly flow returns by Wednesday
as ridging builds to the west. A more defined mid level wave moves
through the Plains mid week. Periodic showers and storms are
possible but confidence is low in timing of precip given mostly weak
forcing with waves and timing differences in models. Temperatures
largely near to above average.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 621 AM CDT Thu Jul 3 2025

A few isolated storms this morning along/east of I-29 will
continue to move east/southeast through mid/late morning. Have
added a TEMPO group for KSUX for an hour for -TSRA, but
lightning could diminish by the time it reaches the terminal.
Outside of morning convection, dry through the period. Have seen
some very patchy fog southwest of KHON and in other obs around
the US Highway 14 corridor this morning. Any MVFR/IFR conditions
will be brief and end by mid morning.

Winds through the period gust 20 to 25 knots out of the south.
LLWS is possible tonight across the area as the LLJ strengthens;
however, only included at KHON where more model guidance shows
a stronger jet and a bit more of a directional shift. Confidence
is low in occurrence given the potential for mixing/gusts into
the overnight hours.

&&

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

&&

$$

DISCUSSION...SG
AVIATION...SG