767
FXUS63 KFSD 172334
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
634 PM CDT Wed Jul 17 2024

.KEY MESSAGES...

- Patchy fog may develop in river valleys and other low lying areas
  early Thursday morning.

- Below normal temperatures will continue through the weekend as northerly
  flow filters cooler air into the region.

- Low to moderate rain chances (30%-70%) will return this weekend,
  highest Friday night into Saturday. While exact location and
  timing remain uncertain, an isolated severe storm risk and
  pockets of heavy rain are possible during this period.

&&

.DISCUSSION...
Issued at 156 PM CDT Wed Jul 17 2024

TONIGHT AND THURSDAY: Satellite images for early this afternoon show
a broad diurnal cumulus field. A shallow, weakly unstable layer
could bring occasional sprinkles or brief light showers through
early this evening. Otherwise cooler than normal temperatures, low
humidity, and a light northeast wind make for excellent conditions
for outdoor activities tonight and Thursday. The atmospheric pattern
over the Northern and Central Plains remains largely stagnant in dry
northern flow aloft with strong 1022mb sfc high pressure centered
over MN. This pattern favors at least patchy fog development early
Thursday morning with 12z HRRR guidance suggesting areas of fog at
least in river valleys and/or low lying areas around dawn.

On Thursday morning, a weak ridge riding shortwave slides through
western SD/central NE. This may bring a few light showers into south
central SD, but the main impact is much more likely to be slightly
increased cloudiness. Otherwise expect another pleasant day with a
light south wind gusting into the teens west of I-29 and highs in
the mid 70s to mid 80s.

THURSDAY NIGHT AND FRIDAY: Low (<30%) chance for isolated showers
and storms develops with warm air advection and another weak ridge
riding shortwave late Thursday night into early Friday west of I-29.
Aside from this, should still see largely drier conditions than wet
through at least the first half of Friday. Warm air advection brings
subtly warmer and more humid conditions as well, with highs again in
the mid 708s to mid 80s.

Chances for scattered showers and storms increase heading into
Friday afternoon and night, triggered by a strengthening northern
stream shortwave gliding south into the region. Moderate instability
and 20-30 kts 0-6km deep layer shear would suggest potential for
isolated/marginal strong to severe multicell storms. With a messy
wind profile and fairly weak winds aloft, large hail, damaging wind
gusts, and locally heavy downpours remain the main threats with the
strongest storms Friday afternoon and night.

SATURDAY AND BEYOND: Though there will be breaks/dry periods,
isolated to scattered showers and storms are expected to linger
through Monday with good model agreement in the maturing upper low
stalling over IA/NE. This brings fairly humid, though mild (highs in
the 70s and 80s) weather for mid-late July.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 634 PM CDT Wed Jul 17 2024

VFR conditions are expected to prevail this TAF cycle. Should see
winds become light and variable near sunset and continue throughout
the overnight period. Direction then becomes southerly by mid-
morning Thursday under mostly sunny skies.

&&

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

&&

$$

DISCUSSION...BP
AVIATION...SST