349
FXUS63 KFSD 230344
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1044 PM CDT Sat Jun 22 2024

.KEY MESSAGES...

- Ongoing flooding may worsen as the runoff from the last 24
  hours makes its way to the waterways. Record river flooding
  is likely on several basins.

- Dry conditions with seasonal temperatures are expected Sunday,
  however a hot and humid air mass returns on Monday. Monday
  high temperatures are expected to rise into the 90s with heat
  indices nearing or exceeding 100 degrees, especially for the
  SD/NE/IA tri-state region.

- The pattern through mid week doesn`t favor any long duration
  rain, but several brief risks for passing convection exist. A
  more prominent low pressure system moves in later in the week
  and weekend.

&&

.DISCUSSION...
Issued at 220 PM CDT Sat Jun 22 2024

Shortwave energy responsible for morning/early afternoon
convection continues to exit the region, although can`t rule
out an isolated diurnally driven shower or thunderstorm over
parts of south central South Dakota this evening. Otherwise,
high pressure and large scale subsidence is expected for the
overnight hours and into Sunday, resulting in dry conditions.

The progressive upper level pattern will continue into next
week. Another low pressure system will develop out of the
Rockies on Monday. Return flow winds and strong WAA advection is
expected out ahead of the system Monday afternoon. Model
dew point temps rise back into the upper 60s/low 70s with NBM
giving a 99% probability of CAPE values soaring above 2000 J/KG.
That said a healthy CAP and lack of forcing should prevent
thunderstorm activity during the afternoon hours. Afternoon max
temperatures will be on the rise, with highs into the 90s.
Combined with humidity, apparent temperatures will be nearing or
exceeding 100 degrees in some locations, especially along and
south of I90. 500 MB height falls/shortwave energy are more
prominent during the late Monday night into Tuesday morning time
frame however. A low POP exists in this time frame and the
region is outlooked for a marginal (1 out of 5) chance for
severe weather.

High pressure will again build in for Wednesday. However, the
end of the workweek appears to be active once again. Near zonal
upper level flow on Thursday will transition to southwest flow
aloft for Friday and into the weekend. This pattern will again
set up the return flow/gulf moisture tap and WAA on Thursday
with a fairly well organized low pressure system moving through
Friday and Saturday. Multiple rounds of showers and
thunderstorms are possible.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1044 PM CDT Sat Jun 22 2024

Potential for fog is the main aviation concern tonight. With winds
already calm and variable, as we cool towards our crossover
temperatures patchy to areas of fog are expected to form during the
overnight period into Sunday morning. This appears most likely for
areas along and east of the James River Valley, and given the wet
antecedent conditions, patchy to areas of fog are expected with
visibilities below 1 mile possible. Given spatial uncertainties,
kept mention of fog limited to tempo groups for the TAF sites. VFR
conditions return after any remaining fog dissipates Sunday
morning.

&&

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

&&

$$

DISCUSSION...AJP
AVIATION...APT