833
FXUS63 KFSD 140350
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1050 PM CDT Thu Jun 13 2024

.KEY MESSAGES...

- 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 (60-90%) on Saturday, though amounts are less certain.
  NBM probabilities for an inch of rain are in the 30-50% range
  for areas east of the James River Valley.

- Active weather pattern is expected for next week with
  potential for severe weather, though details are uncertain.

&&

.DISCUSSION...
Issued at 148 PM CDT Thu Jun 13 2024

Rather pleasant this afternoon, with light northerly winds and
temperatures largely in the upper 70s and 80s. This is occurring
as weak ridging builds off to our west, with a surface high
pressure moving down from southern Canada into the overnight
hours. While dewpoints have been dropping throughout the day,
they peaked in the upper 50s to lower 60s earlier today. With
overnight temperatures expected in the mid to upper 50s, cross
over temperatures will likely be reached, so similar to last
night we will likely see patchy fog in low-lying areas along
with the river valleys.

While we`ll see the ridging aloft continue into the morning hours,
the current closed off upper level low moving ashore onto southern
California turns into a shortwave overnight into Friday, and will
eject onto the central plains late Friday morning. With the surface
high pressure sliding off to our east and a weak developing surface
low pressure off to our west, southeasterly surface flow develops
and will advect warm and moist air back into the region. As a
result, another afternoon with high temperatures in the lower to mid
80s. Given weak isentropic flow on the backside of the surface high
in addition to weak shortwaves out ahead of the main wave, may start
to see some weak showers and isolated thunderstorms develop in south-
central South Dakota by the early afternoon hours. As the surface
high is pushed eastwards, chances for light rain expand eastwards
into the evening hours. Not impossible to see a strong wind gusts in
along and west of the MO River Valley in south-central SD along the
leading edge of the warm front, but the location of said front may
end up further west keeping severe chances very low across the area.

Overnight, a strong low-level jet develops as stronger shortwaves
out ahead of the main wave move overhead. While both of those could
create some thunderstorms prior to the main wave, the highest
chances for showers and thunderstorms arrive late overnight into the
morning hours on Saturday. High resolution convection allowing
models (CAMs) all show a mesoscale convective system (MCS) to some
capacity moving towards the region overnight into the morning hours,
slowly dissipating through the morning hours as the storms outrun
the instability. Chances for additional thunderstorms return in the
afternoon as shortwaves continue to move across the region, with non-
zero chances for severe weather returning as well. Chances for
severe weather will be dependent on how the MCS changes the
environment, specifically the position of the warm front/sector by
Saturday afternoon. SPC has areas along and east of the James River
Valley in a threat level 1 out of 5, but again details remain
uncertain, so if you have outdoor plans on Saturday afternoon make
sure to check on the weather before heading out. Given the numerous
chances for rain, temperatures on Saturday will be a touch lower in
the mid to upper 70s for areas east of I-29, while normal
temperatures in the 80s are expected for areas west of I-29 as they
get some afternoon heating.

Overnight into Sunday the low pressure system will likely have
pushed through the area, though some models have this occurring
later in the day, which will bring an end to the rain chances
from this system. Models that have the rain chances ending
earlier show a rapid warm-up is expected, bringing afternoon
temperatures up into the mid 80s to lower 90s, while those that
are slower with ending the rain keep us in the upper 70s to mid
80s.

The pattern remains active into next week as southwesterly flow
aloft continues due to a strong upper level ridge expected to
develop along the east coast, in addition to a strong either cut-off
upper level low or deep trough along the northwestern CONUS. This
sets us up to potentially see periodic chances for rain and severe
weather 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 similar
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 /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1040 PM CDT Thu Jun 13 2024

Ensemble guidance hints at some patchy fog development in low
lying areas and river valleys through early Friday morning;
however, will keep out of TAF sites for now given low confidence.
Winds remain light and variable overnight, shifting southerly
through early Friday afternoon. Gusts to 20 knots are possible.
Shower and storm chances begin to increase toward the end of the
period west of the James River, but will keep mention out of
KHON for now. VFR conditions prevail outside of fog and
convection.

&&

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

&&

$$

DISCUSSION...APT
AVIATION...SG