493
FXUS63 KFSD 180316
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1016 PM CDT Tue Sep 17 2024

.KEY MESSAGES...

- Breezy southerly winds continue, the strongest west of the
  James River. Gusts 30 to 45 mph late this afternoon through
  the overnight period.

- Greater chances for rain (40-60+%) tonight through Wednesday,
  mainly focused late tonight west of I-29. Moderate (~ 50%)
  probability of rainfall exceeding 0.25", but low (< 30%)
  probability of exceeding 0.50".

- Moderate chances (40-60%) for showers/storms late week into
  the weekend, with highest chances currently focused Friday
  night through early Sunday. Exact timing and location remain
  uncertain.

&&

.DISCUSSION...
Issued at 255 PM CDT Tue Sep 17 2024

CURRENT THROUGH TONIGHT: Showers and thunderstorms that impacted the
region this morning have largely diminished, with latest
observations showing breezy south/southeasterly winds and
temperatures in the 70s to lower 80s. Should see gusts between 25 to
40 mph continue this afternoon, with the strongest generally along
and west of the James River.

Upper level low lifts northeastward across Montana/North Dakota this
evening, causing precipitation chances to return overnight ahead of
an advancing cold front. Still a bit of variability amongst the
latest CAMS, though most show showers/storms impacting those along
and west of the James between 06-09z. While severe weather in not
expected at this time, can`t rule out the possibility of seeing
gusts up to 50 MPH, small hail, and lightning. QPF amounts have
trended lower with the latest forecast cycle, suggesting most
locations will see less than a quarter of an inch.

WEDNESDAY AND THURSDAY: Upper level low deepens Wednesday, with the
aforementioned cold front progged to push eastward across the region.
Will likely see showers/storms reach the I-29 corridor prior to/near
daybreak, with activity over southwest Minnesota and northwest Iowa
expected through the afternoon. That being said, latest guidance
does show showers/storms breaking up a bit as they moves across the
CWA so coverage may become a bit more isolated through the
afternoon. Some CAMs also suggest redevelopment would be possible
during the late afternoon/evening, which may pose a marginal severe
threat. Still not entirely confident if we will destabilize enough
to achieve this, but if storms were to go, believe gusts up to 60
MPH would be the primary hazards with CAPE between 1000-1500 J/kg.
Lapse rates still remain meager (< 7 degC/km), suggesting hail
should remain around or less than quarter size. In any event, we
encourage you to have a way to receive warnings in the event that
storms become strong to severe. Though some isolated to scattered
activity may still be possible Thursday, think we should trend
toward drier conditions through the afternoon and evening.
Otherwise, look for highs in the 80s and lows in the 50s to 60s to
prevail during this time.

FRIDAY ONWARD: Weak ridging builds aloft Friday, allowing dry
conditions to prevail briefly before the next shortwave takes aim at
the region Friday night into Saturday. Still quite a bit of
variability in place concerning the track and evolution of this
wave, making it hard to put too much confidence behind any one
solution just yet. Nonetheless, most have the better precipitation
chances (40-60%) occurring south of I-90 through the weekend. For
now, will continue to monitor trends and make further refinements as
confidence grows. Otherwise, look for notably cooler temperatures to
return, with highs mainly in the mid to upper 60s. Overnight lows
will also feel a bit crisp, with temperatures falling into the 40s
to lower 50s.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1016 PM CDT Tue Sep 17 2024

Breezy south-southeast winds gusting into the 20s will be decreasing
into the morning hours, with scattered showers and thunderstorms
expected to move in prior to 1 am for areas west of the James River
Valley. With stronger winds aloft out of the south, a few more hours
of LLWS are expected, with greatest LLWS west of I-29. The
showers/storms will be moving northeast, with areal coverage
expected to expand eastwards into the morning hours as the
showers/storms become more isolated. Will likely see a couple hour
break from the rain from mid/late morning hours into the mid
afternoon, when additional showers/storms may be possible,
especially east of I-29. Very isolated severe thunderstorms may be
possible, with gusts to 60mph being the main threat.

&&

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

&&

$$

DISCUSSION...SST
AVIATION...APT