146
FXUS63 KFSD 172345
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
545 PM CST Sun Nov 17 2024

.KEY MESSAGES...

- Widespread rain chances (70%-100%) return from Monday
  afternoon through Tuesday. Rain rates up to 0.25" inches/hr
  could lead to accumulations up to 1.00+ inches in areas east
  of Hwy-281.

- Light snow will be possible mostly north of I-90 from Tuesday
  night to Wednesday. However, uncertainty still remains in
  exact amounts.

- Breezy to strong northwesterly winds are expected on Tuesday
  and Wednesday with wind gusts between 40 to 50 mph possible.

- Cold wind chills in single digits to teens will be possible on
  both Tuesday night and Wednesday night.

&&

.DISCUSSION...
Issued at 230 PM CST Sun Nov 17 2024

REST OF THE EVENING/TONIGHT: A mild and quiet day continues!
Taking a look across the area, mostly clear conditions persist
as a weak surface high slides to the south and southeast of our
area. Looking aloft, warm air advection (WAA) should begin to
strengthen this evening with the arrival of the upper-level
component of the high. While this won`t mean too much for
tonight, the stage is almost set for tomorrow`s precipitation
chances. Lastly, another cool night is on the horizon as
temperatures drop towards freezing with the coolest conditions
north of I-90.

MONDAY-WEDNESDAY: Heading into the new week, quieter conditions
will continue through the first half of Monday as warm air
advection (WAA) strengthens on the backside of the amplified
ridging. As more warm and moist air pools into our area
throughout the morning, expect our temperatures to gradually
warm into the upper 40s to low 50s for the day. From here, cloud
cover will gradually increase from south to north ahead of a
well agreed upon ULL that will lift into our area by late Monday
morning. As our rain chances (70%-100%) gradually increase into
Monday afternoon, the combination of weak instability along
with strong mid-level frontogenesis will lead to widespread
light to moderate showers with a few heavier showers having
rainfall rates up to 0.25" inches/hr according to the HREF.
With this in mind, accumulations between 1.00 to 1.25 inches are
expected east of Hwy-281 with areas west of the highway
receiving closer to 0.50"-0.90" of an inch of accumulations. As
this system continues to rotate northeastwards into central MN
by Monday night, expect our rain chances to gradually diminish
from southwest to northeast with most areas being completely
precipitation-free by the mid-morning on Tuesday.

Looking into the rest of Tuesday, quieter conditions return as a
strong push of cold air advection (CAA) move through our area
aloft. This along with northwesterly surface winds will help
kick start our cooler stretch heading into the weekend. However
to start, expect our temperatures to decrease into the low to
mid 40s for the day. From here, the main concerns shift towards
stronger winds and colder wind chills as the SPG tightens. With
this in mind, further analysis of soundings shows up to 40 kts
at the top of the mixed layer with the strongest winds setting
up along and west of the James River Valley. While this does
meet our wind advisory criteria, opted to hold off on issuing
any headlines for now since we`re still a few days out at this
time. Nonetheless, as temperatures drop towards the mid to
upper 20s by Tuesday night; breezy northwesterly winds will lead
to chilly wind chills in the lower to upper teen heading into
the start of the day on Wednesday. With this in mind, make sure
to dress in layers and to avoid prolonged exposure to the cold!

Lastly, as the previously mentioned ULL phases into an approaching
trough by Tuesday night could see a some light snow develop across
areas north of I-90 through Wednesday. While uncertainty still
remains, 17.12z guidance is split on overall amounts with the
Euro/Canadian showing more wrap around moisture than the NAM/GFS
solutions. As a result, its a little too early to determine which
solution will win out at this time. However, most ensemble guidance
continues to show medium to high confidence (50%-80%) in at least a
tenth of a inch of snowfall across most areas with the highest
confidence along the Hwy-14 corridor so we could at least see a
little something to start the day on Wednesday.

WEDNESDAY ONWARDS: Looking into the middle and latter parts of
the week, any lingering snow chances will continue to diminish
as the newly developed ULL rotates eastwards into the Great
Lakes Region. From here, the main concerns continue to be
stronger winds and colder wind chills overnight. Taking a look
at soundings, ample mixing and up to 55 kts at the top of the
mixed layer will continue to promote stronger wind gusts across
the area with the strongest gusts along and west of the James
River. While another wind headline will likely be needed on
Wednesday, will have to look closer into whether a wind
advisory, high wind warning, or a combination of the two is
needed for parts of the area. Shifting gears to wind chills,
colder temperatures in the low to mid 20s overnight along with
elevated northwesterly winds will lead to cold wind chills in
the single digits to low teens towards the start of Thursday.
With this in mind, make sure to bundle up! By Thursday and
Friday, quieter conditions return as ridging and subsidence
moves into the region. Cooler overall conditions will persist
into the weekend as daily highs drop into the low to upper 30s.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 545 PM CST Sun Nov 17 2024

VFR conditions and relatively light winds will prevail through
the nighttime hours and into early morning Monday.

After 14Z-15Z, rain will quickly spread north across much of the
forecast area, bringing a rapid deterioration in ceilings, and
to a lesser extent visibility. By the end of this TAF period,
IFR-LIFR ceilings will be widespread, perhaps just reaching
KHON by 19/00Z. With light to moderate rain expected, MVFR to
locally IFR visibility is also likely.

East winds will increase after daybreak, and especially after
18Z, with gusts 20-25kt prevalent east of the James River Valley
through the afternoon.

&&

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

&&

$$

DISCUSSION...Gumbs
AVIATION...JH