112
FXUS63 KFSD 121953
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
253 PM CDT Wed Jun 12 2024

.KEY MESSAGES...

- A few more hours of hot conditions, with an additional round
  of rain possible (30%) late this afternoon east of I-29. While
  chances are low, isolated to scattered severe thunderstorms
  may develop into the evening hours, with up to 2 inch hail and
  gusts up to 70 mph possible.

- Another round of scattered light showers and thunderstorms
  move across the region during the late overnight hours into
  Thursday morning, with afternoon temperatures again in the
  80s.

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

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

&&

.DISCUSSION...
Issued at 252 PM CDT Wed Jun 12 2024

While we had scattered to areas of showers and thunderstorms
earlier, temperatures have had no problems rebounding back up into
the mid to upper 80s across the region. This is occuring as
temperatures aloft continue to exceed the 90th percentile of
climatology, so with a couple hours left of sunshine, we could still
see areas reach up into the lower 90s before the afternoon is over.
While the earlier thunderstorms were caused by the prefrontal
trough, the cold front itself is still poised to move through the
area later this afternoon into the evening hours. However, the front
itself does not look to create enough lift to overcome the 50-100
J/kg of convective inhibition (CIN) created by the warm-air
advection aloft. So, while we would have 2000-3000 J/kg of CAPE and
45 to 50 knots of bulk shear available to any storm that is able to
break through the cap, additional severe thunderstorm development
appears unlikely as the cap is expected to remain in place.

As we cooldown to our cross over temperatures tonight, we may see
some patchy fog develop in low-lying areas and river valleys, but
overall widespread fog is not currently expected. Otherwise, winds
will be light and variable tonight, with overnight low temperatures
largely in the 60s expected. A weak shortwave moves across the
region late overnight into the morning hours, but as dewpoints drop
down in the 50s and low MUCAPE values of a 100-300 J/kg, only
expecting light rain before the showers exit off to our east. Above
normal temperatures in the lower to upper 80s are still expected for
Thursday, as the cold front largely lowered our dewpoints.

Upper level ridging occurs off to our west overnight into Friday,
with a surface high pressure sliding down from Canada during the
early morning hours. This will keep us closer to our normal
temperatures, in the lower to mid 80s. Upper level ridging breaks
down throughout the day as a potent shortwave ejects onto the
central plains from the rockies, with the first of many shortwaves
moving across the area by Friday evening. SPC has issued a level 1
out of 5 risk for severe thunderstorms. As additional waves move
overhead, periodic chances for showers and thunderstorms continue
throughout the day on Saturday, before ending on Sunday morning.

The pattern remains active into the beginning of next week as
southwesterly flow aloft continues due to a strong upper level ridge
expected to develop along the east coast. This sets us up to
potentially see periodic chances for rain as numerous shortwaves
move across the region, with the inverted trough from a surface low
pressure system also focusing chances for rain across the region.
Model solutions have simliar ideas, but do vary in their placement
of warmest temperatures and highest rainfall chances, so have left
the NBM in place given the uncertainties.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1248 PM CDT Wed Jun 12 2024

Scattered showers and thunderstorms are occurring across the region,
and will likely continue at some capacity throughout the afternoon
hours, especially for areas east of I-29. For areas along and east
of highway 25, can`t rule out an isolated storm or two becoming
severe later this afternoon into the evening hours, with large hail
and strong wind gusts being possible with the strongest storm.
Otherwise, a cold front is starting to move through the area,
swinging the breezy south-southwesterly winds around to become out
of the north-northwest. Wind speeds sharply decrease overnight,
becoming calm and variable before becoming northerly again Thursday
morning.

&&

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

&&

$$

DISCUSSION...APT
AVIATION...APT