829
FXUS63 KFSD 191129
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
629 AM CDT Wed Jun 19 2024

.KEY MESSAGES...

- Aside from a few stray showers east of Highway 60 this
  morning, expect a mostly dry, cooler than normal day.

- Another round of rain spreads in late tonight through Thursday
  night. Severe weather threat is low, but have high confidence
  in widespread rain. Highest rainfall amounts are most likely
  to remain near/north of the I-90 corridor (Little Sioux River
  basin). Probabilities of additional >0.50" totals are high at
  70-80% north of I-90, with 1" probabilities above 50%.
  Isolated amounts of 2-3+ inches are possible.

- Risks for thunderstorms continue into Friday, with potential
  for strong to severe storms Friday afternoon and night.

- Cooler temperatures and likely dry conditions Saturday night
  into early next week, though rain chances return Monday
  night.

&&

.DISCUSSION...
Issued at 419 AM CDT Wed Jun 19 2024

TODAY AND TONIGHT: Radar early this morning shows mid level echoes
based at 10kft sliding into south central SD, which are likely not
resulting in anything aside from increased cloudiness. Further east,
a few stray showers trek northeastward near and east of Hwy 60 in
northwest IA. As the departing stationary front sags south this
morning, model soundings suggest the drying 925-700mb layer will
largely cut off rain aside for perhaps a few sprinkles in northwest
IA this morning. Strong sfc high pressure sliding by to our north
brings light winds and a nice respite from the rain for most of the
region this morning and afternoon. Temperatures remain cooler than
normal for this time of year as cooler air aloft builds in behind
the front departing south. Stratus tracking in from northern SD
should mix out by early afternoon, but cirrus and maybe some cumulus
will linger during the day limiting diurnal heating. Expect highs to
only reach the lower to mid 70s. Little to no weather impacts
continue through the evening, though cloud cover and rain chances
increase from the west overnight as several weak mid level waves
approach in southwest flow aloft.

THURSDAY: Initial warm air advection induced scattered showers and
isolated thunderstorms look likely to enter the region via south
central SD around or after midnight tonight, spreading east through
the region Thursday. With anomalous moisture content via
precipitable water at the top 3% of ensemble guidance for this time
of year, occasional heavy downpours and prolonged moderate rain is
likely with showers and storms spreading through southeast SD and
southwest MN Thursday morning and early afternoon. Weak instability
(<500 J/kg MUCAPE) minimizes severe weather threat, but HREF
probability matched mean rainfall paints a broad 0.50-1.00" swath
near and north of a Yankton to Sioux Falls to Jackson line. Worst
case scenario NAM based guidance suggest a few locations may receive
1-2"+ of rain Thursday morning. While there is still fairly low
confidence in the location of the axis of heaviest rain and exact
amounts, Thursday morning will still be fairly poor for outdoor
activities. More likely to see breaks in the rain Thursday
afternoon than morning, especially south of I-90.

On Thursday night, rain chances ramp up as convective remnants track
in with a wave from the NE Panhandle. Continued high moisture
content coupled with the nocturnal LLJ feeding in primes the
environment for another period of moderate to heavy rainfall. With
the aforementioned stationary front lifted north to near the Hwy 14
corridor, higher confidence in the heaviest rainfall amounts
occurring near and north of the I-90 corridor with a high (>50%)
chance of at least a half inch of rain in this area. North of I-90,
deterministic guidance suggests potential for locally heavy
downpours producing 1-2+" overnight.

FRIDAY AND SATURDAY: As aforementioned front lifts north and puts us
deeper into the warm sector Friday, we`re in for a hot muggy day
with dew points in the 70s and highs in the 80s to near 90 degrees.
Confidence in details regarding breaks in the rain decreases
considerably for Friday and Saturday. However Friday night into
early Saturday brings the next potential for severe weather as the
jet stream sags a bit further south (increasing deep layer shear)
and we destabilize more than previous days ahead of a stronger wave
in zonal flow aloft. Encourage those with outdoor plans
Friday/Friday night to monitor this period for details regarding
severe weather and heavy rainfall threat.

SATURDAY NIGHT AND BEYOND: Deterministic models mostly put us on the
north/dry side of the sfc front by Saturday afternoon, favoring
drier conditions and near seasonal conditions Saturday night through
Sunday. An early look into next week favors a warmer and wetter than
normal pattern continuing.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 627 AM CDT Wed Jun 19 2024

Pockets of MVFR stratus and isolated showers linger in the
region this morning, but confidence is low in these impacting
any TAF sites. Otherwise expect light northwest winds to turn
more northeast and eventually east during the day with VFR
cirrus prevailing in the region.

Another round of showers and storms is expected to spread in
late tonight with IFR to MVFR conditions, locally heavy
downpours, and gusty erratic winds expected at times.

&&

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

&&

$$

DISCUSSION...BP
AVIATION...BP