849
FXUS63 KFSD 231101
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
601 AM CDT Mon Sep 23 2024

.KEY MESSAGES...

- Temperatures remain near to slightly above normal today with
  highs in the low 70s to up to about 80 degrees across parts
  of central South Dakota.

- Chances (20-25%) for scattered light showers return this
  evening and night as a cold front moves through. Rainfall
  amounts at or below a tenth of an inch is expected.

- Temperatures trend back to normal to above normal levels for
  the middle of the week. Chances for precipitation remain low.

&&

.DISCUSSION...
Issued at 201 AM CDT Mon Sep 23 2024

Calm to nearly calm conditions continue through the overnight hours
as a surface ridge continues to slide through the region. With light
to calm winds in place beneath mainly clear skies, shallow patchy
fog is possible. This will most likely take place in and around
river valleys. Any minor patchy fog that does develop will quickly
burn off through the morning hours, resulting in a pleasant rest of
the day! Temperatures will warm to the 70s this afternoon with a few
locations across central South Dakota having the potential to see
highs barely creep into the low 80s ahead of an incoming cold front.
Southerly winds will also be a bit stronger just ahead of the front
with gusts up to 20-25 mph expected. The cold front is tied to a
strong upper level wave which will bring chances for light rain to
the forecast area tonight. This wave is moisture starved though but
the large scale ascent ahead of the wave as well as the cooling from
the base of the wave itself will cool upper an mid level thermal
profiles to saturation. The question will be if the low levels can
saturated via top down saturation. As of now, soundings suggest that
there could be some saturation. At the same time, the same soundings
show a hint of CAPE up to 100 J/kg or less which could be just
enough to develop very weak convection and allow rain to reach the
surface. Rainfall amounts are expected to be light with amounts of a
few hundredths to up to a tenth of an inch expected. Have nudged up
overnight low temperatures in response to the cloud cover associated
with the wave and now have lows bottoming out in the upper 40s to
low 50s.

Isolated light showers could persist into Tuesday morning but as a
whole, Tuesday will be another nice day as high temperatures remain
in the 70s with lows falling to the upper 40s overnight. The
previously mentioned upper level wave will set the stage for the
upper level pattern for the rest of the week as it breaks off from
the strong northern jet stream across Canada as it becomes
vertically stacked over parts of the Midwest. The vertically stacked
low will allow for a narrow area of upper level ridging to get
squeezed over the area. This upper level ridging will allow for a
return of near to above average temperatures in the 70s to even low
80s for Wednesday, Thursday, and Friday.

Beginning on Friday, rain chances have the potential to return to
the area but this chance is uncertain due to how the vertically
stacked upper level low travels. Medium range guidance depicts
different evolutions of this low which, contributing to this
uncertainty. Ensembles also show differing probabilities for a
hundredth of an inch of rain as the GFS and Euro ensembles show a
near zero probability for the end of the week and weekend. The
Canadian ensemble is the main outlier as it`s probabilities are up
to about a 50% chance for exceeding a hundredth of an inch of rain.
Despite these differences, the upper low will remain southeast of
the forecast area which will keep any rainfall amounts to a minimum.

Another chance for rain is possible early next week as medium range
guidance shows the potential for a shortwave trough to pass through
the Northern Plains. There is quite a bit of variance regarding this
waves evolution so have stuck with model blended PoPs for now.
Temperatures look to cool to near seasonable as the wave comes

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 601 AM CDT Mon Sep 23 2024

VFR conditions are expected for the TAF period. Mainly clear skies
and light winds begin the TAF period. Isolated patchy fog is
possible into the mid morning hours, mainly along bodies of water.
Any fog that does develop will be on the shallow side. Aside from
fog, light southerly winds are expected this afternoon with speeds
up to 10-15 knots. Mid level clouds will thicken ahead of an
approaching cold front this evening and night. Light rain showers
are possible this evening and night across the area but dry air may
prevent any rain from reaching the ground. As such, have omitted any
mention of rain from all TAFs. However, trends will be monitored.
Otherwise, winds will turn out of the northwest behind the front to
end the TAF period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers