146
FXUS63 KFSD 120832
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
332 AM CDT Wed Jun 12 2024

.KEY MESSAGES...

- Hot and potentially muggy conditions today will promote the
  development of scattered showers and thunderstorms throughout
  the day with the better chances expected in the morning to
  early afternoon. A few storms could become strong to severe.

- Near to above normal temperatures will continue into the new
  week with daily highs expected to peak the upper 70s to 80s.

- Confidence continues to increase in more widespread rain
  chances by Saturday with periodic chances continuing into the
  early parts of next week.

&&

.DISCUSSION...
Issued at 325 AM CDT Wed Jun 12 2024

The Short Term (Today & Tonight):

A hot and potentially muggy day is ahead. Taking a look at satellite
imagery, mostly clear and quiet conditions continue this mornings as
most areas wake up to temperatures in the in the low to mid 60s with
dew points in the 50s. Shifting gears to our precipitation chances,
the quiet conditions will likely be short lived as warm air
advection (WAA) strengthens ahead of a lifting mid-level trough
shortly after daybreak this morning. This along with a strengthening
LLJ will likely cause a cluster of showers and potentially
thunderstorms to develop west of the James River as our elevated
instability climbs towards 1000 J/kg between 12z-15z this morning.
As this developing cluster of showers thunderstorms push eastwards
towards the I-29 corridor, can`t completely rule out a stronger
storm or two by the late morning (15z-18z) as mid-level lapse rates
approach 7 degrees C/km. This along with increasing instability
(1500-2000 J/kg) and 30-40 kts of 0-6 km shear should be a conducive
environment for large hail development up to golf ball size. Looking
aloft, the surface cold front will then drift southeastwards
throughout the day and into the evening hours. Ahead of it,
southerly to southwesterly surface winds will increase as better
mixing is achieved resulting in wind gusts between 20-30 mph by the
afternoon hours.

With a westerly component of the wind in play and strengthening
WAA advection aloft, expect our temperatures and dew points to
respond accordingly as highs peak in the upper 80s to upper 90s
across the area. This along with dew points in the 60s will make
for some sticky conditions outside for most of the afternoon as
heat indexes approach the low to upper 90s with some low
potential (<10%) for values up to 100 degrees in some spots
along the Missouri and James River Valleys. With this in mind,
make sure to stay hydrated and to wear lighter clothing if
possible. Looking at our afternoon potential, high resolution
guidance has started to shy away from any afternoon develop
mostly due to the development of a strong cap as the warm sector
moves overhead. While there is still some potential for some
gradual development east of I-29 ahead of the cold front, mostly
thinking the cap will keep things confined to light to moderate
showers than true thunderstorms which has resulted in decreased
confidence in our afternoon potential. However, IF (and it a
big if) a few accelerating updrafts were able to overcome the
cap with the help a low-level boundary; these parcels would have
access to about 2000-3000+ J/kg of MLCAPE and 40-45 kts of deep
layer shear which would be conducive for up to 2 inch hail and
damaging winds in excess of 70 mph. Lastly, while widespread
heavy rain isn`t expected; accumulations up a quarter inch will
possible under developing convection. By tonight, conditions
should begin to clear behind the cold front as temperatures drop
into the upper 50s to mid 60s for the night.

The Long Term (Thursday-Tuesday):

Heading into the extended period, a few light to moderate showers
will likely develop closer to daybreak on Thursday as a subtle
shortwave slides just north of our area. While only light
accumulations are expected, most of the developing activity should
be focused north of I-90. With a shift to northerly to northwesterly
surface winds and plenty of cold air advection (CAA) aloft, surface
temperatures will decrease heading into the weekend as a surface
high approaches the region. As a result, daily highs will likely
only peak in the low to mid 80s on both Thursday and Friday. Our
attention will then pivot to the Colorado Rockies by Friday night as
a series of mid-level shortwaves lifts northeastwards towards our
area setting up more widespread precipitation chances through
Saturday. While exact details remain uncertain due to variability
among deterministic guidance, ensemble guidance continues to show
low to medium confidence (30%-50%) in up to half an inch of QPF
across our area. Nonetheless, most of the developing activity
should be out of the area by sometime Sunday morning as quieter
conditions return with the arrival of a mid-level ridge.

From here, long-range deterministic guidance begins to diverge in
potential solutions as large-scale height rises shift us to
southwesterly flow pattern aloft. Some deterministic guidance
does show some potential for periodic rain chances on Monday and
Wednesday. However, with the variance among solutions its too
early to tell how things will pan out. As a result, left the
default NBM POPs in the extended period. Lastly, temperatures
will continue to trend above normal heading into the early parts
of next week with highs expected to be largely in the low to
upper 80s from Sunday through Tuesday with a few low 90s
possible across northwestern IA.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1043 PM CDT Tue Jun 11 2024

Expect light and variable winds to gradually turn southeasterly
through the overnight period, with gusts between 15 to 25 MPH
possible near/after daybreak. As alluded in the previous discussion,
will see showers and storms impact the region, with an initial wave
likely near daybreak, with perhaps another round of redevelopment
possible during the afternoon/evening. A few storms may become
strong to severe, resulting in brief periods of MVFR cigs/vsbys.
That being said, confidence still remains low concerning the exact
location of these storms as model guidance continues to vary - so
for now only have vicinity mention. Will continue to monitor trends
and adjust as necessary. Otherwise, should see quiet conditions
return by the end of the period.

&&

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

&&

$$

DISCUSSION...Gumbs
AVIATION...SST