153
FXUS63 KFSD 261132
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
632 AM CDT Wed Jun 26 2024

.KEY MESSAGES...

- River crests have already occurred or will occur within the
  next 24 hours.

- An active pattern aloft brings multiple rain chances through
  the forecast period with the most widespread chances expected
  on Thursday and Friday and again early next week.

- Chance of one inch or more of rainfall between now and
  Saturday morning is low (< 30%); however, any thunderstorm
  could produce locally heavy rainfall (1" or more) Thursday
  through Friday.

&&

.DISCUSSION...
Issued at 352 AM CDT Wed Jun 26 2024

CURRENTS: More pleasant start to the morning (comparatively
speaking) with 3 AM temps in the 60s and dew points in the upper 50s
to mid 60s. Most of the area is dry, although an area of showers
embedded in mid level cloud deck is sliding southeast from
northeastern SD toward the Hwy 14 corridor early this morning with a
weak wave and LLJ. So far, rainfall amounts with this activity over
the last 6 hours have been a 0.10" or less, and it has been
weakening as it moves south. Winds from the northeast have been
periodically breezy with gusts 20-30 mph.

TODAY: Any lingering showers this morning will come to an end as the
mid level wave and LLJ weaken through the early morning hours. Any
precip which reaches the grounds should be very light (a couple of
hundredths. Pleasant and cooler weather on tap today with CAA and
north to northwesterly flow aloft as mid level ridge builds to the
west. Plenty of sunshine today with highs in the 70s to lower 80s.
Breezy conditions this afternoon across southwestern MN and
northwestern IA with gusts around 20 mph.

TONIGHT THROUGH FRIDAY: Our general reprieve from active weather
will be short lived, as the next mid level wave ejects into western
SD by tonight. Forcing from the initial weak wave and push of WAA
should be enough to develop showers and storms across western SD,
which move east through the overnight hours, reaching the I-29
corridor by rush hour. Lows tonight in the 50s and 60s. Scattered
showers and isolated storms continue to move east during the day
Thursday with another wave tracking through the weak ridge, all
ahead of the more defined low in the western CONUS. Cooler on
Thursday with lots of cloud cover and scattered showers around, only
in the 70s. Trough axis and surface low track east through Thursday
night and Friday, keeping at least isolated shower and storm chances
in place. Lows Thursday night in the 60s with highs Friday in the
upper 70s and 80s. Tightening surface pressure gradient leads to
breezy southerly wind Thursday, shifting to northwesterly behind the
cold front through the day Friday.

Severe weather risks are low, but not zero during this time frame.
For Thursday and Thursday night, better instability remains off to
the west; however, some of the guidance is showing an axis of
stronger instability (1500 J/kg of CAPE or so) and bulk shear around
30-35 knots during the afternoon and evening as the elevated warm
front lifts north. So can`t entirely rule out an isolated stronger
storm during this time, although confidence is low given ensemble
probability of at least 1000 J/kg of CAPE only around 25%.
Otherwise, on-going convection across western SD will likely weaken
as it moves into the MO River Valley and toward the I-29 corridor
overnight. For Friday, instability increases during the afternoon as
we sit in the warm sector ahead of the cold front. Ensemble
probability of over 1000 J/kg of CAPE Friday afternoon/evening
climbs to 80% near/east of I-29 with similar probability for over
1500 J/kg. Mid level lapse rates 6.5-7 deg C/km and increasing bulk
shear to 40 knots or so would support some stronger storms if storms
can break the cap.

Widespread heavy rainfall looks unlikely, with chances of over an
inch of rain between this morning and Saturday morning less than 30%
for much of the area. However, PWATs climbing to around 2" and
increased moisture transport would support some locally heavy
rainfall with thunderstorms of an inch or more.

SATURDAY ONWARD: Brief mid level ridging for the weekend, with
mostly dry weather expected outside of a very low chance with a mid
weekend short wave. More robust troughing begins to take shape for
the beginning of the week with periodic rain and storm chances
returning. Temperatures generally near to below normal during this
time, warming toward the beginning of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 625 AM CDT Wed Jun 26 2024

Isolated showers this morning continue mainly for the Hwy 14
corridor southeast along the I-90 corridor of southwestern MN into
northwestern IA - these are expected to taper off through
mid/late morning. Have left mention out of KHON and KFSD given
sparse coverage west of the Buffalo Ridge. VFR conditions
prevail through much of the period with a few clouds around.
Winds will vary in direction from northwest to east to southeast
through the period.

Additional shower and isolated storm chances increase from west
to east after 27.06z, reaching the I-29 corridor toward 27.12z.
Did add a PROB30 group for KHON, but omitted from KFSD with this
issuance.

&&

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

&&

$$

DISCUSSION...SG
AVIATION...SG