524
FXUS63 KFSD 292327
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
627 PM CDT Wed May 29 2024

.KEY MESSAGES...

- Multiple chances for showers and thunderstorms starting late
tonight and continuing into next week.

- A Marginal Risk (Level 1 of 5) for severe storms is in place for
much of our area Thursday, with damaging winds and large hail being
the primary hazards. Additional strong to severe storms may occur
over the weekend, especially Sunday afternoon through early Monday
morning.

- Near normal temperatures and periodic breezy conditions continue
through the weekend, with above normal temperatures forecast to
prevail heading into the new week.

&&

.DISCUSSION...
Issued at 254 PM CDT Wed May 29 2024

CURRENT THROUGH FRIDAY NIGHT: Pleasant conditions continue across
the region, with latest observations showing mostly sunny skies and
temperatures in the lower 70s. S/SE winds during this time have also
become fairly during this time, with gusts between 20 to 30 MPH
noted in areas along and west of the James River. Elsewhere, have
seen gusts mainly range between 10 to 20 MPH.

Expect breezy winds to continue this evening, with cloud cover
forecast to gradually increase ahead of an advancing upper level
trough. WAA also increases ahead of this feature, causing
precipitation chances to return to our area near/shortly after
midnight. That being said, latest CAMs continue to show a line of
showers and storms splitting as it approaches the western fringes of
our CWA - with one area of precipitation tracking along and north of
Highway 14, and the other skirting along the MO River Valley.
Showers and storms then look to form a more cohesive line prior to
daybreak just west of I-29.

As alluded to in the previous discussion, could see an additional
line of storms develop during the early afternoon/evening ahead of
an advancing cold front, though this development will largely depend
on how the morning plays out. If showers diminish early and we get a
decent amount of clearing, may be able to destabilize enough to see
a few strong to severe storms with the aforementioned line. While
shear remains rather meager, a few deterministic models show upwards
of 500-1000 J/kg of MLCAPE. GFS ensemble also shows a 40-70% chance
of exceeding 500 J/kg, whereas the EC ensemble only showcases a 20-
40% chance. Do think it`s worth noting, that SPC`s latest Day 2
Marginal (Level 1 of 5) Risk has been expanded to include much of
our area. As with any severe weather, we strongly encourage you to
have a way to receive warnings.

On the flip side, if showers linger longer than expected and we stay
cloudy most of the morning and early afternoon, think it will be
difficult to see additional development, especially in regard to
severe storms. Rather, would be more concerned with the potential
for locally heavy rainfall as PWATs continue to increase. That being
said, the risk for flash flooding still remains low, with 1 hour
guidance for most areas west of I-29 over 1.5". Nonetheless, can`t
rule out the possibility of seeing some ponding in urban and low-
lying areas with poor drainage. Localized rises on smaller
tributaries may also occur.

Trough axis swings north of the area on Friday, with another weak
short wave ahead of it, although this wave may stay largely to our
south. This keeps at least scattered activity around through the end
of the week, especially along and east of I-29. In regard to
rainfall totals, currently have amounts through Friday evening
ranging between half an inch to just over an inch. Otherwise, look
for highs to remain in the 70s, with lows generally in the 50s.

SATURDAY THROUGH WEDNESDAY: Upper level trough slides across the
International Border through the first part of the weekend, with
quasi-zonal flow Saturday. Latest guidance would suggest a lull in
precipitation Saturday morning/early afternoon, followed by another
round of showers and storms for the remainder of the weekend. While
a few strong to severe storms may occur Saturday afternoon, believe
the better chances will occur Sunday afternoon through early Monday
morning. Both CIPS and CSU Machine Learning probabilities continue
to suggest a 10-15% chance of seeing severe weather across our area.
Latest EC/GFS ensembles also show high probabilities (>70%) of our
area seeing CAPE exceed 1000 J/kg, with moderate probabilities (40-
60%) of CAPE exceeding 2000 J/kg. In addition to this, latest
guidance shows steep mid level lapse rates (>7 degC/km) and PWATs
greater than an inch. Certainly something to keep an eye on,
especially if you have outdoor plans this weekend. Active weather
continues heading into the new week, with afternoon highs forecast
to rise into the low to mid 80s - a taste of things to come this
summer!

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 619 PM CDT Wed May 29 2024

VFR conditions are expected for the first half of the period.
Clouds increase over night as the next storm system approaches.
Showers and thunderstorms are possible after midnight and
through the day Thursday. Under showers and thunderstorms,
expect ceilings will decrease to MVFR with some reductions in
visibility also possible under stronger storms.

Winds will be southeasterly and breezy, sustained at 10-20 kts
with gusts 23-27 kts. Strongest winds are currently west of the
James River Valley but will progress eastward overnight. By
sunrise most of the region will be experiencing the stronger
winds. KHON is at risk of some LLWS from approximately 30.06Z
until 30.12Z. Speed shear between 1500-2000 ft AGL of 45 kts is
possible.

&&

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

&&

$$

DISCUSSION...SST
AVIATION...AJP