271 
FXUS63 KFSD 241727
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1227 PM CDT Sun Oct 24 2021

.SHORT TERM...(Today and Tonight)
Issued at 358 AM CDT Sun Oct 24 2021

Early morning satellite imagery shows mostly cloudy skies across the 
region, with radar showing scattered showers moving across the area. 
There have been some isolated thunderstorms occurring west of the 
James River Valley with roughly 100 J/kg of CAPE, but that will be 
dwindling throughout the rest of the morning hours. The rainfall is 
courtesy of a mid-level wave and associated surface low, with the 
latter currently shown to be tracking over the eastern half of 
Kansas as per surface observations. Rainfall amounts with this 
system have come in a touch drier, likely due to the on going 
convection further south of the region preventing better moisture 
returns for the area, as has been alluded to in previous 
discussions.

Scattered showers north of I-90 will be courtesy of the mid-level 
wave, and thus will likely be weaker as they have less moisture to 
pull from. Further south, as the low continues to lift 
northeastwards, expect scattered showers to spread out across the 
area as a surge of mid-level frontogenesis moves into the region. 
Isolated thunderstorms are possible across portions of NW Iowa as a 
ribbon of weak instability will be available to tap into for the 
remaining morning hours, likely remaining along/south of the Highway 
20 corridor. 

By the afternoon hours, the region will be northwest of the surface 
low and under the developing TROWAL, allowing for scattered showers 
to continue for areas along and east of I-29. This is also when 
strongest wind gusts are expected in NW Iowa, where isolated gusts 
to 30 mph will be possible. Areas west of I-29 will likely also see 
some scattered showers throughout the afternoon hours, but as before 
these will be caused by the mid-level wave continuing to move 
eastwards across the area. As both the mid-level wave and surface 
low continue to track eastwards throughout the evening hours, chances 
for precipitation dwindle with areas in NW Iowa likely seeing rain 
exit off into central Iowa by midnight. Overall, areas in and 
adjacent to NW Iowa will likely see amounts around 3/4 of an inch, 
while areas in SE South Dakota and SW Minnesota will likely remain 
at or under 1/4 of an inch. Expect cloud coverage to decrease as 
this system departs to our east, with overnight lows Monday morning 
in the mid 30s. 

.LONG TERM...(Monday through Saturday)
Issued at 358 AM CDT Sun Oct 24 2021

Ridging aloft builds across the region throughout the day on Monday 
but with a surface high developing across northern Ontario, a quick 
warm-up is not expected with afternoon highs right around 50 
degrees. A developing surface low in Montana will lead to a 
tightened SPG across central SD, with gusts west of the James River 
Valley near 25 mph. The ridge breaks down overnight into Tuesday as 
our next long wave trough and associated low pressure begin to move 
eastwards, which will cause breezy conditions to continue throughout 
the day Tuesday. Gusts will be ranging from 25 to 35 mph before 
decreasing into the evening hours, but on the plus side WAA in the 
developing warm sector will bring us back into the mid to upper 50s. 

Chances for rain return Tuesday evening as medium/longer range 
guidance all depict a long wave trough moving over the region, 
becoming negatively tilted with a surface low that moves across the 
Mississippi River Valley. However, how they go about doing so leads 
to considerable uncertainty regarding timing/locations/amounts. 
Ensemble solutions don't offer much help as they continue to be 
rather underdispersed with this system. While those details will 
still need to be ironed out, a dynamic system such as this will lead 
to rainfall throughout the day on Wednesday and likely into Thursday 
so have left the populated guidance as is since it seems like a 
reasonable solution for the time being. Temperatures will likely be 
right around average throughout this period, with a brief warm-up 
into the weekend as some sort of ridging looks to form on the 
backside of the previously mentioned long-wave trough. 

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1226 PM CDT Sun Oct 24 2021

Scattered showers continue across the region, causing cigs and vsbys 
to approach MVFR levels, with IFR levels currently being observed at 
KSUX. Should continue to see these showers push eastward this 
afternoon, allowing dry conditions and VFR levels to gradually 
return to the region later this evening. Otherwise, look for 
northerly/northeasterly winds to prevail overnight, with winds 
forecast to become southeasterly by tomorrow afternoon. 

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...APT
LONG TERM...APT
AVIATION...SST