780
FXUS63 KFSD 120344
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1044 PM CDT Tue Jun 11 2024

.KEY MESSAGES...

- Scattered showers and storms expected Wednesday, with the
  better chances in the afternoon and evening east of I-29. A
  few storms could be strong to severe.

- Near to above normal temperatures continue through early next
  week, with the warmest day expected Wednesday.

- Next more widespread chances for rain anticipated on Saturday,
  with periodic chances into early next week.

&&

.DISCUSSION...
Issued at 250 PM CDT Tue Jun 11 2024

REST OF TODAY/TONIGHT: Near to slightly above average temperatures
this afternoon despite northwesterly flow. Temperatures continue to
climb into the mid and upper 80s for most of the area. Scattered
diurnal cumulus clouds continue to develop, but expect the area
to stay dry through this evening. Breezy northwesterly wind gusts
to around 30 mph are expected to drop off with the diurnal CU
around/just after sunset. Lows tonight remain a touch on the
warmer side falling into the 60s. WAA begins to increase through
the overnight as the next system approaches as well, with winds
beginning to shift to the south and increase toward daybreak.

WEDNESDAY/WEDNESDAY NIGHT: Some isolated showers and storms may
develop during the morning hours with the WAA and the elevated
trough. Elevated instability may climb near/above 1000 J/kg west of
the James River before roughly 12.15z (10 AM) ahead of the trough.
Can`t entirely rule out a stronger storm during this time if a storm
is able to develop given the steep mid level lapse rates above 7 deg
C/km. Surface cold front sinks southeastward through the day and
into the evening hours. Ahead of it, we`ll continue to see
southwesterly flow, allowing temperatures to climb into the 90s.
Breezy winds expected between the diurnal mixing and tightening
surface pressure gradient. Although winds will be out of the
southwest, should see dew points climb into the 60s in the warm
sector. These temps and dew points allow our instability to climb
into the afternoon and evening hours, with ensemble data showing
a > 60% chance of exceeding 2000 J/kg of CAPE. Some deterministic
models show 3000+ J/kg possible across our eastern CWA during
the afternoon and evening hours. Shear increases as the LLJ
strengthens over our eastern forecast area, climbing to around
40-45 kts - with directional shear as well near the surface
front. Mid level lapse rates increase as well, around 7.5 deg
C/km. All of these parameters indicate the potential for all modes
of severe weather (especially during the afternoon and evening
hours). Large hail to 2" diameter, damaging wind gusts to 70
mph, and a couple of tornadoes are all possible. Threats may
vary with storm mode; more discrete cells may prevail during the
morning and into the early part of the afternoon with the
WAA/pre-frontal trough and potentially more linear storm mode
should things fire near/along the surface cold front later in
the afternoon/evening. Widespread heavy rain is not expected,
but could see brief heavy rain with thunderstorms.

Now, there is some lingering uncertainty in the location and
coverage of any potential development. A few questions and issues.
First question is what, if any, impact elevated morning convection
could have on the early afternoon convection. The other big
question is whether or not there is enough forcing ahead of the
front to fire any convection and if so, where and what is it. As
mentioned in the previous discussion, deterministic guidance
continues to vary in where/when/how strong any mid level wave
over the area will be. The prefrontal trough timing/strength may
also varies between the models. Models also vary in the timing
and the surface front, which would impact the location of the
surface development. If the front moves fast enough, this
convection may develop just east of our CWA. The final uncertainty
I`ll mention is whether or not we reach our convective
temperatures (yes, even with highs climbing into the 90s) - many
of the deterministic guidance keeps convective temps around 33+
deg C (which is the lower to mid 90s). With the cap in place,
we`ll need something to break.

Main takeaways for tomorrow`s forecast: hot and a bit more humid with
showers and storms through the day. Coverage and timing of storms
remains in question, although better chances will be later in the
day. Storms could quickly become strong to severe with all hazards
in play. Stay weather aware and have at least one way to receive
warnings should any be issued for your area. Check the forecast
for updates, and ensure you have a severe weather plan.

THURSDAY ONWARD: With mid/upper jet to the north and a subtle
700mb wave and area of frontogenesis dropping south, may see
some isolated showers during the morning hours on Thursday.
Confidence is low though, with models struggling with which
layer(s) may saturate enough for showers/sprinkles. Any
rainfall amounts would be light, likely just a couple of
hundredths. Highs near to above normal Thursday.

Surface and mid level ridge build in across the Plains late week,
with a few waves trekking through the mid level pattern. Near to
above normal temperatures remain in place through the weekend (highs
in the 80s to lower 90s and lows in the 50s and 60s). Next trough
and surface low swing through Saturday which will bring our next and
possibly more widespread shower and storm chances. Models struggle
to resolve subsequent waves into the latter half of the weekend and
the early part of next week - but could see occasional showers and
storms into early next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1043 PM CDT Tue Jun 11 2024

Expect light and variable winds to gradually turn southeasterly
through the overnight period, with gusts between 15 to 25 MPH
possible near/after daybreak. As alluded in the previous discussion,
will see showers and storms impact the region, with an initial wave
likely near daybreak, with perhaps another round of redevelopment
possible during the afternoon/evening. A few storms may become
strong to severe, resulting in brief periods of MVFR cigs/vsbys.
That being said, confidence still remains low concerning the exact
location of these storms as model guidance continues to vary - so
for now only have vicinity mention. Will continue to monitor trends
and adjust as necessary. Otherwise, should see quiet conditions
return by the end of the period.

&&

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

&&

$$

DISCUSSION...SG
AVIATION...SST