Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 222323

Area Forecast Discussion
National Weather Service Sioux Falls SD
623 PM CDT Wed May 22 2024


- Breezy conditions prevail through the end of the work week,
  with increasing south winds Thursday, and west-northwest winds
  Friday, gusting to 30-35 mph.

- Clusters of strong to severe thunderstorms are possible from
  late Thursday afternoon into early Friday morning. Level 2 of
  5 risk for severe storms through the Missouri and James River
  Valleys, with a Level 1 of 5 risk to the northeast. Large hail
  and damaging wind gusts would be the primary threats.

- Periods of unsettled conditions continue into early next week,
  though confidence in timing/location of favored precip chances
  is low. Higher confidence that temperatures will be on the
  cool side of normal for much of the Memorial Day holiday
  weekend, coldest on Friday.


Issued at 254 PM CDT Wed May 22 2024

TONIGHT: Surface ridge from eastern Nebraska to central South Dakota
this afternoon will move across the forecast area tonight. Lingering
gusty west-northwest winds and diurnal cumulus will diminish this
evening, with winds turning southerly late tonight/early Thursday.
Warm advection with the southerly flow should result in increasing
mid-level clouds, and cannot rule out a few sprinkles across our
northwest counties late tonight, though deep sub-cloud dry layer
should limit potential for measurable precipitation.

THURSDAY-THURSDAY NIGHT: Much of Thursday will be dry, with the day
dominated by increasing southerly flow and mild temperatures ahead
of an approaching cold front. Gusts 30-35 mph will be common by late
morning and through the afternoon, as temperatures climb into the
mid 70s to around 80. The southerly flow will draw increasing low
level moisture northward, with a narrow ribbon of mid-upper 50s dew
points into our western counties ahead of the front. This will help
support a tongue of stronger instability west of the James River by
late afternoon with MUCAPE values 1500-2500 J/kg. Forecast soundings
show a pretty stout capping inversion above 850mb through 20Z, but
this cap weakens through 22Z-23Z, allowing for rapid development of
storms along the cold front by late afternoon/early evening across
our far western counties. Moderate deep layer shear of 30-40kt
along/ahead of the front should support some organized storms, with
steep mid level lapse rates yielding a threat of large hail up to
golf ball size, while initially dry mid levels and DCAPE values
above 1000-1500 J/kg supporting a potential for damaging wind gusts
to 70 mph with initial development.

As the evening progresses, more favorable instability and DCAPE
become focused along/south of the Missouri River Valley (SD/NE state
line), which should likewise focus the greater threat for severe
storms through the southern portions of our forecast area from mid-
evening into the early overnight hours. Storms may be increasingly
elevated the night progresses which may result in hail becoming the
dominant threat. However, the dry mid-levels persist, and with an
increasing low level jet at/above 2kft AGL, could still see some
isolated strong to severe gusts punch through the stable boundary
layer as well. Storms projected to push east of the forecast area by
08Z-09Z, though could see some lingering light showers into early
Friday morning.

FRIDAY-SATURDAY: A trailing wave rotating around the main mid-upper
level low may produce some lingering light showers or an isolated
storm into the day Friday, but otherwise looking at a brief stretch
of dry but cooler weather as we head into the weekend. Coldest temps
aloft swing through during the day Friday, which should keep highs
in the 60s at best, combined with brisk west-northwest winds gusting
as high as 30-35 mph. Slight warming builds in for Saturday, though
temperatures look to remain on the cool side of normal with highs in
the upper 60s-lower 70s for the start of the Memorial Day weekend.

SUNDAY-MEMORIAL DAY: Cooler than normal temperatures persist across
the area as we head through the latter half of the holiday weekend.
A stronger trough looks to dig into the region Saturday night-Sunday
with another wave diving across the region in the northwest flow.
These systems could produce scattered showers and perhaps a few
storms, but instability and shear are both on the weaker side, so
not looking at a severe risk at this point.

TUESDAY-WEDNESDAY: Mid-upper level ridging builds in behind the
departing weekend system, bringing dry weather and warming
temperatures through the middle of the week.


Issued at 623 PM CDT Wed May 22 2024

VFR conditions are expected for the TAF period. Light to marginally
breezy southwesterly flow begins the TAF period along with a CU
field across the area. The CU field will dissipate as mixing ceases
this evening. Winds will also weaken and turn southerly for the
overnight hours. The low level jet (LLJ) will strengthen tonight and
create low level wind shear (LLWS) along and west of the James River
tonight, including at KHON. There is also a chance of sprinkles
tonight around KHON but have omitted from KHON`s TAF as confidence
is too low in sprinkles reaching the surface. Southerly winds become
breezy tomorrow with gusts up to 20-30 knots expected. These
conditions will finish out the remainder of the TAF period.

The other aspect to tomorrow is the chance for showers and
thunderstorms towards the end of the TAF period. Storm development
is likely across central and south central South Dakota but the
exact time of initiation is a bit uncertain at the moment. As such,
have left any mention of showers and storms out of all TAFs but will
be monitoring this potential.