998
FXUS63 KFSD 151121
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
621 AM CDT Mon Jul 15 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms will continue mainly
  across southwestern MN through the mid-morning with a few
  stronger storms possible. Additional scattered showers will be
  possible with a secondary wave through the evening hours.

- As area of thicker wildfire smoke pushes eastwards across our
  area today, skies may become a bit milky through this
  evening. However, no surface impacts are expected at this
  time.

- An active weather pattern will continues into the
  middle/latter parts of the week with periodic low shower and
  storm chances. Starting Tuesday, temperatures will begin a
  cooling trend with highs dropping below our seasonal normals.

&&

.DISCUSSION...
Issued at 414 AM CDT Mon Jul 15 2024

The Short Term (Today & Tonight):

Taking a look across the area, another warm and muggy night
continues as temperatures sit in the upper 60s to low 70s across the
area with dew points in the 60s and low 70s. Similar to the previous
days, more wildfire smoke is expected to push through the area this
morning. While surface impacts will likely be kept to a minimum,
skies may become a bit milky towards the midday as a thicker plume
of smoke pushes across the I-29 corridor through the early
afternoon. Looking northwards, our main focus continues to be on the
developing Mesoscale Convective System (MCS) currently situated over
eastern North Dakota and portions of northeastern South Dakota.
Looking at the environment up there, the MCS is currently working
with about 1500-2000 J/kg of MUCAPE and 50-60 kts of deep layer
shear as it continues its gradual develop. With pattern recognition
signaling that the MCS will likely take its environment with it,
expect this developing line of showers and thunderstorms to follow
the 850-350 mb mean winds which has due easterly flow through the
ND/MN border then east-southeasterly flow across central and
southern MN. With this in mind, expect this activity to arrive in
our area between 09z-10z this morning with the greatest area of
concern being across southwestern MN. Similar to yesterday, the line
of storms will likely be strong to severe with the primary hazards
being large hail up to hen egg size (2 inches) and damaging winds up
to 70 mph. With this line expected to quickly progress through our
area, expect most of the severe threat to be out of our area by 14-
15z.

Unfortunately, our rain chances won`t likely stop there as a
secondary shortwave interacts with a weak 850 LLJ as early as
14z leading to renewed shower and thunderstorm chances (20%-30%)
throughout the day. However, there likely will be a low-end
severe weather risk associated with this developing activity by
the afternoon hours. Taking a look at the environment, we`ll
have plenty of instability and shear with 1000-2000 J/k of
MLCAPE and 30-40 kts of deep layer shear respectfully.
Nonetheless, as we continue to warm throughout the day the
question becomes if any of the developing parcels can overcome
the cap between 700-800 mb. If so, storms will quickly become
severe with golf ball sized hail and damaging winds up to 65 mph
being the primary threats. If not, expect most of the
developing activity to stay sub-severe with pockets of heavy
rain and frequent lightning being the primary threats. Shifting
gear here, with high expected to peak in the mid to upper 80s
and low 90s for the day; elevated dew points in the upper 60s
to low 70s will lead more muggy conditions with heat index
values up to 100 degrees possible through this evening. With
this in mind, make sure to stay hydrated and to avoid prolonged
outdoor activities if possible. Lastly, as cold air advection
(CAA) begins to funnel into the area behind today`s series of
waves; expect our overall temperatures to gradually cool with
overnight lows expected to decrease into the upper 50s to mid
60s.

The Long Term (Tuesday-Sunday):

Heading into the extended period, an active pattern continues aloft
as the Hudson Bay trough drifts southeastwards into the Northern
Plains and Great Lakes regions on Tuesday. Scattered showers with a
few rumbles of thunder will develop by mid-morning as bits of
isentropic lift interact with the left exit region of weak upper-
level jet ahead of a weak shortwave across northeastern SD. Expect
this developing activity to quickly migrate to southeastwards into
our area throughout the afternoon before exiting to our south by the
evening hours. While confidence is low, an isolated strong storm or
two isn`t completely out of the question as developing showers
approach the Missouri River Valley. Looking at the environment,
instability will be limited except along a narrow corridor extending
from Gregory to Yankton which is where 500-1000 J/kg of MLCAPE
resides. Combine this with the 30-40 kts of unidirectional
shear already available and there is a small chances for large
hail up to the size of quarters. However, everything would have
to play out just right for this to occur. With this risk in
mind, SPC has outlined the Missouri River Valley in a marginal
risk (Level 1 of 5) for severe weather. From here, cold air
advection (CAA) will continue to funnel into our area through
Wednesday helping our temperatures gradually decrease below our
seasonal normals. With this in mind, highs will decrease into
the 70s and low 80s through Wednesday with overnight lows in the
50s to low 60s.

Looking into the latter parts of the week, much quieter conditions
will continue through Thursday as the upper-level ridging situated
over the western CONUS builds. By Friday, more shower and
thunderstorm chances (20%-30%) will return as a strengthening upper-
level low (ULL) intersects with increasing warm air advection over
our area. While some details remain uncertain due to intensity and
location differences among medium-range guidance, ensemble guidance
shows low to medium confidence (20%-40%) in up to 0.50" an inch of
QPF through Saturday with the highest probabilities situated along
the Missouri River Valley. Otherwise, expect any developing activity
to exit the region by Sunday morning as the ULL gradually sinks
southwards. Lastly, expect temperatures to stay near to below normal
through Sunday as highs top out in the 70s to low 80s.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 607 AM CDT Mon Jul 15 2024

Mostly VFR conditions with occasional MVFR ceilings will be
possible this TAF period mostly due to developing showers and
thunderstorms. Looking at current radar imagery, scattered
showers and thunderstorms continue to develop along and north
of the Hwy-14 corridor. Expect this activity to gradually drift
southeastwards through the mid-morning before pushing out of
our area. Additional shower and thunderstorm chances will be
possible through this afternoon as another wave slides through.
However, much of the activity will be scattered with most of it
clearing our by this evening. Otherwise, expect light southerly
winds to become northwesterly behind the cold front this morning
conditions with marginally breezy conditions expected through
sunset.

&&

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

&&

$$

DISCUSSION...Gumbs
AVIATION...Gumbs