546
FXUS63 KFSD 150915
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
415 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 an 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 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 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 another muggy day 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. 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 /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1053 PM CDT Sun Jul 14 2024

VFR conditions begin the TAF period. Showers and storms have
developed across North Dakota late this evening and look to grow
into a complex as they progress southeastwards through the night.
The storms look to remain along and northeast of a De Smet, SD to
Luverne, MN to Spencer, IA line. While away from all TAF sites, have
included VCSH in KFSD`s TAF as some trailing showers could impact
the terminal. Should see the complex of storms push east/southeast
of the area by mid morning tomorrow.

A second round of lighter showers is possible during the afternoon
hours but confidence is only high enough to include in KHON and
KFSD`s TAFs as of now. A cold front will push through the area
during the morning hours which will turn surface winds to out of the
north. More storms could develop during the afternoon hours on the
cold front but confidence is low in where storms could develop at
this time. Any chance for showers and storms will push
east/southeast of the area by the evening hours, leaving light
northerly winds to finish out the TAF period.

&&

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

&&

$$

DISCUSSION...Gumbs
AVIATION...Meyers