593
FXUS63 KFSD 200740
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
240 AM CDT Sat Jul 20 2024

.KEY MESSAGES...

- Unsettled weather through the rest of the weekend, with widely
  scattered showers and thunderstorms again Saturday and Sunday.
  Some funnel development may be possible Saturday afternoon
  along a weak surface front.

- Many outdoor events this weekend will want to make sure
  to have an eye on the radar as activity this weekend will be
  rather variable in location and rapid to develop.

- Cooler temperatures continue into next week, with near daily
  rain chances. Rain however won`t impact all locations, and
  will be very hit-or-miss.

- Temperatures will begin to climb upwards for the second half
  of the week, with 50-70% probabilities of 90 degree
  temperatures along and west of the James River by Friday.

&&

.DISCUSSION...
Issued at 237 AM CDT Sat Jul 20 2024

THIS Morning: Stratus and fog continue to develop this morning under
an axis of light and variable winds through the Tri-State area.
There seems to be a weak surface convergence zone extending from
northeast Nebraska into northwest Iowa and southern Minnesota.
Water vapor imagery this morning showing a broad trough through the
Upper Midwest, but it also shows a more compact circulation moving
south along the SD/MN border.  Lift increasing ahead of this wave
should allow for redevelopment of scattered showers over
eastern Nebraska and northwest Iowa through daybreak. Elsewhere,
fog and stratus continues, with some potential for locally
dense fog along and north of I-90.

TODAY: Widely scattered showers may continue across northeast
Nebraska into northwest Iowa through the morning hours.  Despite the
unknowns on how much ongoing stratus development clear today,
isolated to scattered shower or thunderstorm development may begin
to take place along a weak surface trough stretching through the
Tri-State.  Not a highly unstable environment with tall and very
thin CAPE profiles only 500-800 J/KG on average.  However NSTP and
VGP parameters along the boundary indicate at least some updraft
stretching potential that may result in a few brief funnels. Most
of this activity should dissipate by the evening.

TONIGHT:   Another night of light winds may lead to fog development
into Sunday morning, though perhaps there may be enough stratus
around to  limit the overall fall of temperatures and fog potential.

SUNDAY: We`ll remain stuck with a broad upper trough over the
eastern half of the CONUS Sunday. A quiet morning will giveaway
to scattered shower and thunderstorm development in the
afternoon and early evening as a subtle shortwave embedded in
the flow moves southward. This activity is not expected to
become severe, and the overall coverage only supports low PoPs
at this time.

MONDAY-WEDNESDAY:  Scattered showers and thunderstorm risks will
continue nearly every day into the middle of the week thanks to
rather weak low-lvl flow but broad upper level troughing through the
northern US. Most of this non-severe activity will diminish by
sunset each day, but if any more sustained lobe of vorticity can
develop, then activity could linger into the early overnight hours.
The overall heavy rain risk remains low as PWAT values drop
significantly.  However any slowing storm could produce very
localized 1-2" totals.  Temperatures will remain slightly below
normal in the upper 70s to lower 80s.

THURSDAY-FRIDAY: Heights begin to rise by the middle and end of this
week as ridging stuck over the Rockies and West Coast moves east.
We`ll begin to see breezy southerly winds develop Thursday surging
moisture back north and pushing a low-lvl thermal ridge into the
Western Plains.  By Friday low-lvl winds turn more southwesterly,
advecting warm low-lvl temperatures eastward.  Ensembles support
rising temperatures into the upper 80s to 90s by the end of the week
and into next weekend. ECE/GEFS all show 50-70%+ probabilities
of temperatures >90+ along and west of the James river Friday,
and these probabilities spread east for next weekend. Dry
conditions are likely at this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1031 PM CDT Fri Jul 19 2024

Fog and stratus are expected to develop tonight as winds
continue to become light. MVFR to IFR conditions are expected
with this development. Less certainty near KSUX into
northwestern IA where showers may redevelop overnight into early
Saturday, so went with rain over fog in prevailing. Stratus
continues into Saturday evening especially along/east of I-29
with low pressure pivots off to the east.

Uncertainty continues through the TAF period with isolated to
scattered convection into Saturday night. 20.00z models are
becoming a bit more isolated with coverage for areas north and
west of KFSD, so narrowed and delayed PROB30 group for KHON.
Showers and storms could produce locally heavy rain, reducing
visibility to MVFR or IFR conditions.

Above the stratus, thicker wildfire smoke is expected over the
area through the period. This should remain aloft, around 20kft
or higher. Winds shift to easterly toward Saturday afternoon.

&&

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

&&

$$

DISCUSSION...Dux
AVIATION...SG