791
FXUS63 KFSD 111718
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1218 PM CDT Tue Jun 11 2024

.KEY MESSAGES...

-While the severe weather risk remains on Wednesday,
 uncertainty remains on exactly where storms will develop.

-Near to above normal temperatures will continue into the
 weekend with warmest day expected to be Wednesday.

&&

.DISCUSSION...
Issued at 402 AM CDT Tue Jun 11 2024

The Short Term (Today & Tonight):

Another warm and marginally breezy day is ahead. Taking a look
across the area, lingering light showers continue to push eastwards
ahead of a cold front roughly positioned along a Huron to Gregory
line. As this frontal boundary continue to sweep southeastwards
throughout the morning, conditions should begin to clear from west to
east as surface wind become more northwesterly. As the cold front is
quickly replaced by a mid-level ridge, the SPG will tighten leading
to some marginally breezy conditions from the James River eastwards
with gusts up to 25 mph possible by the afternoon hours. Otherwise,
increasing warm air advection (WAA) and deep mixing with help
temperatures increase slightly from the previous day with highs
expected to peak in the low to upper 80s by this afternoon. Lastly,
with increasing WAA advection expected overnight and light southerly
winds, expect our overnight temperatures to stay a touch above
normal with lows expected to be in the low to mid 60s.

The Long Term (Wednesday-Sunday):

Heading into the extended period, hot and muggy conditions
return by Wednesday as the 850mb thermal ridge strengthens
overhead. Increasing warm air advection (WAA) along with a
southerly to southwesterly surface wind will help pull more warm
and moist air into the region which will result in a notable
increase in surface temperatures from the previous day. The
resulting highs will likely vary between the upper 80s to 90s
for the day with the warmest conditions along the Missouri River
Valley. Shifting gears to our precipitation chances, isolated
to scattered showers and thunderstorms will be possible
Wednesday afternoon mostly east of I-29. However, the overall
severe weather risk still remains uncertain mostly due to how
split deterministic guidance is on how the fast the mid-level
will progress through the area with its associated cold front.

On one hand, the GFS/NAM have the faster solution where convection
develops entirely over south-central and southeastern Minnesota by
21z where the nose of the upper-level jet resides. On the other
hand, the Euro/Canadian have the slower solution where the base of
wave sits across the center of our CWA with convection firing across
southwestern MN and our far eastern most column of counties.
While its still a bit too early to determine which solution will
prevail, the environment is still primed to promote moderate
destabilization with 2000-3000 J/kg of MLCAPE and 40-50 kts of
deep layer shear which are consistent among deterministic
guidance. This along with DCAPE values of 1000 J/kg and mid-
level lapse rates of 7 degree C/km will create an environment
favorable for large hail up to golf ball size and damaging
winds up to 65 mph with any developing discrete supercells
initially. While the probabilities are low, an isolated tornado
isn`t completely out of the question either. As things grow
more upscale after 00z, the primary threat will shift more
towards damaging winds. Lastly, with the mix of severe weather
hazards; areas along and east of I-29 are outlines in a Day 2
Slight Risk.

Looking into the latter parts of the week, a few scattered morning
showers will be possible by Thursday morning as mid-level
frontogenesis strengthens along the departing cold front. However,
only light accumulations are expected. Otherwise, lingering cold air
advection (CAA) aloft along with northerly to northwesterly surface
winds will keep our temperatures closer to our seasonal averages
as highs take a slight dip into the upper 70s to low 80s on
Friday and Saturday as heights rise with the approaching upper-
level ridging. Looking ahead, confidence continues to increase
in a multiple rounds of showers and storms from Friday night
into the day on Saturday as multiple mid-level waves lift out
of the Colorado Rockies into our area. While some uncertainty
remains on the severe weather risk and exact amounts, most
ensemble guidance shows low to medium confidence (30%-60%) in up
to half an inch of QPF for this time period. Lastly, increasing
mid-level WAA ahead of the cold front on Saturday along with
southerly to southeasterly surface winds will help temperatures
warm back up into the mid to upper 80s on both Saturday and
Sunday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1207 PM CDT Tue Jun 11 2024

VFR conditions prevail through the period. Showers and
thunderstorms develop Wednesday, which could briefly reduce
categories to MVFR or IFR. Isolated activity is expected in the
morning and afternoon hours. More scattered showers and storms
are possible in the afternoon and evening hours. Confidence is
very low in location of development and evolution, but better
chances later in the day look to be near/east of I-29. A couple
of storms could be strong to severe with large hail and
damaging winds the main threats.

Otherwise, winds this afternoon will gusts around 25 knots out
of the northwest. Light and variable winds tonight, shifting to
southerly through the overnight hours into early Wednesday.
Gusts tomorrow again around 25 knots.

&&

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

&&

$$

DISCUSSION...Gumbs
AVIATION...SG