455
FXUS63 KFSD 030338
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1038 PM CDT Tue Jul 2 2024

.KEY MESSAGES...

- Any lingering shower activity will continue to clear by this
  evening.

- Another round of scattered showers with isolated thunderstorms
  will be possible Wednesday afternoon for areas west of I-29.
  Strongest thunderstorms may be capable of quarter-sized hail
  and gusts to 60 mph.

- An active pattern aloft will lead to multiple rain chances
  throughout the week with more widespread chances (60%-90%)
  occurring on Thursday.

- Slightly cooler temperatures will continue for most of the
  week with highs expected to be between 5-10 degrees below
  normal mostly due to the multiple precipitation chances.

&&

.DISCUSSION...
Issued at 403 PM CDT Tue Jul 2 2024

REST OF THE AFTERNOON/TONIGHT: A wet and dreary day continues!
Taking a look at radar, our main focus continues to be in
northwestern IA along the cold front as areas of light to
moderate showers and isolated thunderstorms continue to push
northeastwards with the isentropic lift associated with a nearby
shortwave. As the base of the main wave swings through our area
this evening, could see some additional light showers develop
along and west of I-29. However, expect the majority of this
activity to slowly exit our area by sunset tonight.
Accumulations will likely vary between 0.25"- 0.75" of an inch
with isolated pockets of 1.00"+ possible underneath heavier
cells. From here, expect the cloud cover to slowly diminish from
west to east overnight as a weak surface low slides to our
southwest. Otherwise, lingering cold air advection (CAA) and
light surface winds will lead below normal temperatures
overnight as lows fall into the upper 50s to low 60s.

WEDNESDAY: Heading into the extended period, an active pattern
continues aloft as quasi-zonal flow returns. By Wednesday, a
much warmer day will be on tap as weak warm front slides along
the SD/NE boarder. This combined with southerly to southwesterly
surface winds and efficient mixing will allow our highs to make
a temporary return to the low to mid 80s for the day. By
Wednesday night, our attention will then shift to the Rockies as
the influx of warm and moist air coupled with the arrival of a
quick shortwave triggers the development of some scattered
showers and thunderstorms over portions of southcentral and
southeastern SD. While the severe risk associated with this
developing activity is still a bit questionable, the environment
ahead of the activity could be favorable for damaging winds
with inverted V soundings and 30-40kts of speed shear present.
However, with limited instability (500-1500 J/kg); the question
becomes how far east does the severe threat extend before
diminishing which is uncertain at this time. With this in mind,
the general expectation is for any developing activity to
gradually weaken as it approaches the James River Valley.

THURSDAY/FRIDAY: By the end of the week, our attention will
again pivot to the Rockies by Thursday morning as an open mid-
level wave begins to occlude over our area leading to more
widespread showers and thunderstorm chances (60%-90%) through
Friday. While the exact timing and potential amounts are still a
bit uncertain at this time, medium-range ensemble guidance
continues to show low to medium confidence (20%-50%) in up to an
inch of QPF through Friday with the highest probabilities
occurring over southwestern MN. Looking into the environment
for this time period, long-skinny CAPE profiles with between
500-1000 J/kg of instability along with 40-50 kts of shear
ahead of the closed low could result in an isolated severe
weather risk by Thursday afternoon east of I-29. However, the
severe weather risk will be conditionally dependent on 1. how
quick the atmosphere can recover from the morning activity and
2. if things can clear out enough for true convection to
develop. Either way, the environment combined with low LCLs will
likely promote some potential for cold air funnels. Lastly,
while the bulk of the precipitation is expected to fall from
Thursday night into Friday morning, could see additional
precipitation chances develop on the back side of the ULL
through late Friday afternoon. Shifting gears to temperatures,
the increased precipitation chances will likely lead to below
normal temperatures to start the weekend with highs varying
between the upper 60s to upper 70s on both Thursday and Friday.

REST OF THE WEEKEND/MONDAY: Looking into the rest of the
weekend, quieter conditions will temporarily return by Saturday
as a quick mid-level ridge slides through the region.
Unfortunately, the quieter conditions will be short-lived as
more precipitation chances potentially return from Sunday night
into Monday as a deepening long wave trough swings through the
region. However, with timing and progression difference among
long-range guidance its too uncertain to make out the finer
details at this time. Lastly, near to just below normal
temperatures will continue through Monday as highs peak in the
upper 70s to low 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1038 PM CDT Tue Jul 2 2024

Patchy fog remains the biggest aviation concern as we reach our
cross over temperatures, with models continuing to indicate best
chances (20-30%) for patchy fog should occur along the southern Big
Sioux and other low-lying areas south of I-90. Would not be
surprised to see chances for fog expand, but for now have kept
chances for fog mention only for the KSUX terminal. Dry conditions
continue into the morning hours, before chances for scattered
showers and thunderstorms return throughout the afternoon hours well
west of I-29.

&&

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

&&

$$

DISCUSSION...Gumbs
AVIATION...APT