885
FXUS63 KFSD 290852
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
352 AM CDT Wed May 29 2024

.KEY MESSAGES...

- Dry, breezy, and mostly sunny today. Multiple chances for
  showers and thunderstorms starting late tonight and continuing
  into next week.

- An isolated strong to severe storm is possible on Thursday
  into Thursday night. A few storms this weekend may become
  strong to severe. Locally heavy rainfall is possible.

- Near normal temperatures prevail with periodic breezy
  conditions into early next week.

&&

.DISCUSSION...
Issued at 350 AM CDT Wed May 29 2024

TODAY: High pressure overhead is leading to a pleasant morning with
calm to light winds, temperatures in the upper 40s to lower 50s, and
clear skies. Can`t rule out some patchy fog toward daybreak, but
should be short lived. Surface high pressure slides to the east
through today, with mid level ridging following suit. WAA increases
as the next wave/trough begins to approach from the west. South to
southeasterly winds also increase as the high pressure slides off to
the east and the surface pressure gradient tightens. West of the
James River, sustained winds could reach 20 mph with gusts 30 to 35
mph. Elsewhere, expect winds to be around 10-15 mph and gusts around
20-25 mph. Highs climb into the 70s. Mostly sunny skies prevail.

TONIGHT THROUGH FRIDAY NIGHT: Trough slides east this evening and
tonight. Ahead of this, WAA continues across our area which with the
leading forcing from the initial short wave, should provide enough
forcing for showers and thunderstorms to develop in western SD and
move east through the overnight hours. Most of the 29.00z guidance
shows the wave and precipitation splitting our forecast area - with
one area of precipitation tracking along/north of Hwy 14 and the
other skirting well south of the MO River. Another round of showers
and storms looks to develop near the cold front during the later
morning and early afternoon. Some of the deterministic models
(namely the NAM and the RAP) show instability increasing to near
2000 J/kg of CAPE; however, confidence is fairly low that we`ll be
able to recover that much instability given the potential for
morning showers and storms with the main push of WAA. This is also
true given that ensembles show a < 40% chance of 1000 J/kg of CAPE
by tomorrow evening. If the atmosphere can recover that much, can`t
rule out an isolated strong to severe storm during the early
afternoon through the evening hours, but think that with mid level
lapse rates around 5.5 deg C/km, 0-6km bulk shear around 20 kts, and
freezing levels around 12kft, severe risk looks very low. Slightly
more concerned with the potential for locally heavy rainfall than
this time yesterday, as guidance is increasing with PWATs and QPF
over the area, now showing widespread values near 1.5". Ensembles
show a very low chance (< 15%) of seeing this much rain in 24 hours.
Flash flood risk is still low, with 1 hour guidance for most areas
west of I-29 over 1.5" but can`t rule out some ponding and localized
rises on smaller tributaries. Lows tonight in the 50s. Highs in the
lower to mid 70s.

Showers and storms slowly push off to the east - slowly - through
the day on Friday, with continued redevelopment ahead of the surface
cold/stationary front, with another short wave passing off to the
south and the trough axis off to the north. Showers and isolated
storms will linger for most of the day, especially along and east
of I-29. Total rainfall amounts through the end of the week of
widespread 0.5" (> 60% chance), and about a 30% chance of exceeding
an inch or more, mainly south of I-90. Current QPF is near the 50th
percentile of guidance. Again, think that flash flood risk is low
through Friday, but will have to keep an eye on trends especially
if heavier rain falls Thursday/Thursday night.

SATURDAY THROUGH TUESDAY: Upper level trough slides across the
International Border through the first part of the weekend, with
quasi-zonal flow Saturday. Models diverge in handling the next wave
Saturday night into Sunday, with a more defined/agreed upon wave
tracking through a portion of the northern Plains late Sunday into
early Monday. This will keep shower and storm chances in place
through the early part of the week. Again, locally heavy rain is
possible with ensemble probs of at least an inch of PWAT over 80%
(and low chances of over 1.5"). Any flash flooding potential would
be dependent on where the heavier precip sets up earlier in the
week. Strong to severe storms are possible over the weekend as
instability and moisture increases. Ensemble guidance shows a high
likelihood (> 80%) of more than 1000 J/kg of CAPE, and moderate to
high chances (> 60%) of over 2000 J/kg. Shear also is on the
increase, along with steepening mid level lapse rate. Other ensemble
and machine learning continues to support at least a 5-15% chance of
severe weather over the area. There remains some uncertainty though
given the variance in models, but those with outdoor plans this
weekend should keep an eye on the forecast. Temperatures will be
near to above normal into early next week. Expect breezy conditions
to prevail as well.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1030 PM CDT Tue May 28 2024

VFR conditions expected throughout the period. Winds will remain
light and variable overnight as they transition towards a
southeasterly direction, with wind speeds increasing throughout the
morning hours. Given the light winds, can`t completely rule out some
patchy fog in the river valleys, but most guidance suggests we
should remain fog-free. Strongest gusts for Wednesday are expected
far west of I-29, where gusts up to 35 mph are possible, whereas
east of I-29 gusts should remain largely in the teens and lower
20s.

&&

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

&&

$$

DISCUSSION...SG
AVIATION...APT