149
FXUS63 KFSD 151700
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1200 PM CDT Wed May 15 2024

.KEY MESSAGES...

- Broken bands of showers and thunderstorms will swing through
  the forecast area this morning & again in the later afternoon
  and evening. Severe weather threat is low, but could see a
  stronger storm or two during the late afternoon/early evening.

- Well above normal temperatures will end the week. Moderate to
  high confidence (70-80%) in widespread highs in the 80s on
  Friday. Lower confidence (30-40%) in highs for Saturday,
  depending on timing of cold front.

- More active southern stream jet is expected next week which
  may bring a better chance for increased shower/ thunderstorm
  coverage.

&&

.DISCUSSION...
Issued at 235 AM CDT Wed May 15 2024

TODAY-TONIGHT: Today begins with a surface low in south central SD,
with showers most prevalent in an area of weak warm advection across
an inverted trough north of the low. As associated mid-upper level
wave slides a bit farther east this morning, surface low will slide
to the northeast and anticipate a broken line of showers and perhaps
a few thunderstorms to expand southward through daybreak before
lifting northeast by midday. This should lead to a relative lull in
activity for a few hours late morning-early afternoon before we see
additional development along an advancing cold front.

Main question for the afternoon revolves around timing of said cold
front, though broad consensus brings the front to near I-29 around
20-21Z, with the northern end pushing east of Hwy 71 in Minneota by
sunset while the southern end lags back across northwest Iowa later
into the evening. May see a narrow ribbon of moderate instability
(1000 J/kg) ahead of the front, though most solutions are on the
weaker side with MUCAPE at or below 500 J/kg. Forecast soundings
show any instability to be rather tall/narrow due to weak mid-level
lapse rates, while deep layer shear is also meager at <30kt. Thus
not expecting severe storms with this activity, though cannot rule
out some small hail or gusty winds with stronger cells.

A trailing wave rotating around the backside of the upper wave may
support some spotty showers behind the cold front this afternoon or
early evening, but thunder with this activity should be more sparse.
Drying behind the cold front should bring an end to most showers by
midnight tonight.

THURSDAY-FRIDAY: High pressure slides east across the forecast area
Thursday, allowing for mostly sunny skies, relatively light winds,
and seasonable highs in the 70s. Increasing southerly flow later
Thursday night into Friday will draw a brief shot of warmer air
northward into the region. Deterministic models showing 850mb temps
+15 to +20C build northward into the forecast area, which should mix
out to widespread 80s for highs Friday. This is also supported by
various ensembles with better than a 60% probability of temperatures
topping 80F over most of the CWA.

FRIDAY NIGHT-SATURDAY: Broad warm advection over the area may lead
to elevated showers/storms Friday night, though better chance for
this activity looks to be north of Highway 14 in line with better
convergence at the nose of the low level jet. Approaching mid-upper
level wave and associated cold front appear to be trending a little
faster on Saturday than previous runs, which would limit additional
highs in the 80s to perhaps the far southeast portions of the CWA.
However, this is still a lower confidence forecast as timing of the
front is still uncertain. Given this trend toward a faster frontal
passage, precip chances for Saturday look limited, perhaps a stray
shower or storm in our far east in the afternoon.

EARLY NEXT WEEK: The first part of the upcoming week is trending a
little more unsettled as a stronger southern stream jet develops
from the southwest CONUS into the southern/central Plains. This will
bring periodic chances for a broader coverage of showers/storms,
though still plenty of uncertainty in specifics to pin down timing
and/or severe potential. Temperatures remain on the warm side of
normal to start the week, though look to trend a little cooler by
Tuesday, again depending on timing of various waves and precip
chances.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1156 AM CDT Wed May 15 2024

Scattered showers and thunderstorms will be possible this
afternoon into the evening. The better chances will be near I-29
through about 22z, then east of I-29 after about 21z through
about 6z. A few of the thunderstorms will be strong with small
hail, lightning and locally heavy downpours possible. MVFR
ceilings will be possible through the afternoon with mainly VFR
conditions outside of the showers and thunderstorms expected
after about 0z.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...08