921
FXUS63 KFSD 161947
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
247 PM CDT Mon Sep 16 2024

.KEY MESSAGES...

- Temperatures remain above normal through mid to late week.
  Nighttime lows show greater departures above normal (10-15F)
  than daytime highs (5-10F) due to anomalously high low level
  moisture/dew points.

- Low (generally < 20%) rain chances through Tuesday afternoon.
  Confidence in timing and placement is low, but expect amounts
  to remain light, with less than a quarter inch through this
  period at any location.

- Greater chance for rain (40-70+%) Tuesday night through
  Wednesday, mainly focused Tuesday night west of I-29. Moderate
  (~ 40%) probability of rainfall exceeding 0.25", but low (<
  25%) probability of exceeding 0.50".

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

&&

.DISCUSSION...
Issued at 246 PM CDT Mon Sep 16 2024

CURRENT: 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. Have seen a few additional showers try to develop along
the MO River Valley over the last hour or so, but dry air in the
lower levels has quickly put a damper on any further upscale growth.

TONIGHT THROUGH TUESDAY: While a lull in precipitation is expected
for much of the evening and overnight period, do have renewed
chances, albeit low (<20%), along and east of I-29 prior to/near
daybreak Tuesday. Latest CAMs have started to come into better
agreement though some variances still exist concerning the duration
and extent of coverage. May need to up PoPs a bit in the coming
shifts if trends suggest a similar story to this morning, where the
increasing LLJ aided convection. As alluded to in the previous
discussion, expect any showers/storms Tuesday morning to push
eastward through the afternoon as the strongest wave and WAA lift
across the area. Though severe weather in not expected at this time,
can`t rule out the possibility of seeing gusts up to 50 MPH, and
small hail. Rainfall amounts look to remain less than a quarter of
an inch.

Similar to today, expect breezy S/SE winds to continue as the SPG
tightens in response to a developing low pressure on the lee side of
the Rockies. Currently have gusts between 25 to 35 MPH, with the
strongest generally along and west of I-29. May see a few areas west
of the James River flirt with Wind Advisory criteria, though the
threat of this remains marginal at this time. Otherwise, look for
afternoon highs to rise into the mid to upper 80s with the aid of
WAA. Lows during this time will also remain quite mild, as
temperatures only fall into the mid to upper 60s.

WEDNESDAY AND BEYOND: Unsettled weather looks to continue through
mid-week as the aforementioned low pressure lifts northeastward.
While the center of this low is still progged to move over the
Montana/North Dakota border, still expect to see impacts across our
area Tuesday night into Wednesday ahead of an advancing cold front.
Given the better dynamics in place, could see QPF range between
0.25 - 0.5 inches, with locally heavier amounts still possible.
Though some isolated to scattered activity may still be
possible Thursday, think we should trend toward drier
conditions, at least through Friday afternoon, before the next
wave arrives Friday evening. That being said, model variability
does increase heading into the weekend, making it hard to put
too much confidence behind any one solution just yet. For now,
will continue to monitor trends and make further refinements as
confidence grows. Otherwise, look for above average temperatures
to continue through Friday. Near to potentially below normal
temperatures will then return over the weekend, though this will
largely depend on the timing and track of the second low
pressure system.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1224 PM CDT Mon Sep 16 2024

VFR conditions are expected to prevail this TAF cycle. Latest radar
imagery shows showers and thunderstorms diminishing across the
region. Could see some redevelopment along the MO River this
afternoon, with largely dry conditions expected to persist
elsewhere. Breezy S/SE winds also look to continue throughout the
period, with gusts between 20 to 30 kts. As alluded to in the
previous discussion, if winds drop off a bit overnight, can`t rule
out seeing some LLWS in areas west of I-29. Otherwise, could see
another round of showers develop prior to daybreak along and east of
I-29. Given the degree of model variability that still exists, have
opted to only include a PROB30 group at KFSD/KSUX for the time
being. Will continue to monitor trends and make adjustments as
confidence increases.

&&

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

&&

$$

DISCUSSION...SST
AVIATION...SST