Weather alerts for the NWS Sioux Falls SD forecast area

000
FXUS63 KFSD 281147
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
647 AM CDT Wed Oct 28 2026

.KEY MESSAGES...

- Patchy fog, some locally dense, will continue to impact the
  area through the morning commute. Though widespread dense fog
  is not expected, be sure to use extra caution on the roads. 
  Fog should lift by the mid to late morning.

- Rain and isolated storm chances return Wednesday into
  Wednesday evening mainly near and east of I-29. If storms can
  develop, an isolated stronger storm capable of ping pong ball
  sized hail and 60 mph wind gusts is possible between 1 PM and
  8 PM CDT.

- Additional rain chances, including a few isolated
  thunderstorms, return late this week into the weekend.

&&

.UPDATE...
Issued at 313 AM CDT Wed Oct 28 2026

Low stratus continues to build northeastward early this 
morning, though we're also seeing some breaks in the clouds 
over portions of northwest Iowa. This has allowed for some fog 
to develop there, which has been locally dense at times. Other 
areas seeing locally dense fog include the higher elevations of 
the Coteau des Prairies where the stratus has lowered enough to 
reach the ground. Slightly elevated winds look to prevent 
widespread dense fog development and thus will hold off on fog 
headlines at this time. Trends will be monitored closely. 
Patchy fog is likely elsewhere, but chances for dense fog 
outside of the previously mentioned areas are low (<30%). Any 
fog should burn off by mid to late morning. 

The main story to watch today will be the chance of thunderstorms
this afternoon as an isolated severe storm remains possible 
mainly near and east of I-29. At this point, the main area to
watch will be closer to the upper level support with the
shortwave ejecting across the upper Midwest. This is where 
shear values will be the highest, mainly over far east central 
South Dakota into southwest Minnesota. Latest guidance is 
showing perhaps a bit better elevated instability collocated 
with this area of higher shear this afternoon. Will increase the
hail size threat to ping pong balls to account for this as some
elevated supercell structures may develop in these areas. 

The chance of surface based storms has further diminished given
models holding onto a surface cap, likely due to the cloud 
cover expected through much of the day today. However, if there 
ends up being less clouds than expected, more heating could 
result in very isolated surface based strong to severe storms. 
Main concern with this will be over northwestern Iowa and far
southern Minnesota where 60 mph wind gusts will be the main 
threat in any surface based storms, along with hail to half 
dollar in size. All that said, currently thinking the better 
chances for severe weather will be east of the area where the 
stronger low level jet will be located, but be sure to keep an 
eye to the sky this afternoon! Timing for an isolated severe 
storm is between 1 pm and 8 pm.

&&

.DISCUSSION...
Issued at 314 PM CDT Tue Oct 27 2026

Clouds will continue to gradually become broken from west to east 
for the remainder of this afternoon and into the evening. Those in 
central South Dakota may get a few glimpses of sunshine yet. Tonight 
winds will be light out of the south, and lows will be in the 40s to 
low 50s. Nearly calm conditions may result in dense fog development 
overnight. Ensemble guidance indicates a broad area of 50-70% 
probability of visibility of 2 miles or less. While the worst 
conditions look to remain along and north of I-90, caution should be 
used everywhere. Fog may linger into the mid-to-late morning.

Looking aloft for Wednesday we see a broad wave taking shape over 
western Canada, extending down over the central High Plains. At the 
surface a low pressure will settle over central Canada and a cold 
front will develop and drape from there through eastern North 
Dakota, central South Dakota, and into southeastern Wyoming. 
Moderate warm air and moisture advection will pool ahead of this 
front, working to destabilize the boundary layer. Highs will climb 
into the 60s to the low 70s over northwest Iowa, while dewpoints 
climb into the upper 50s and low 60s. Though skies will be partly 
cloudy, surface heating through breaks in the clouds may work to 
further destabilize the environment, especially east of I-29. MLCAPE 
of 500-1000 J/kg is possible. Mid-level lapse rates will be marginal 
at 6.5 to 7.0 deg C. However, the 0-6 km bulk shear will be 40+ kts, 
enough to support a stronger thunderstorm or two. As the upper level 
trough, upper right jet entrance region, and surface front move to 
the east scattered showers and thunderstorms are expected to form 
over central South Dakota in the late morning to early afternoon. As 
this system continues to pivot, storms will expand to the east 
mostly along and north of I-90. By mid-to-late afternoon the axis of 
the upper trough and surface front will cross into the area of best 
thermodynamic parameters east of I-29. A few stronger, possibly 
severe thunderstorms may develop. While conditions are favorable of 
surface based supercells, strong boundary layer capping will likely 
keep most storms elevated and sub-severe producing small hail and 
wind gusts to 45 mph. Should a stronger surface based storm develop, 
it could produce large hail up to the size of a half dollar, and 
damaging wind gusts in excess of 60 mph. This matches well with the 
latest SPC Day 2 outlook with a Marginal (level 1 of 5) Risk of 
severe storms. Despite the chance for stronger storms, most will 
only see a few hundredth to a couple tenths of accumulation. Those 
under any stronger storms could see up to an inch. Storms should 
push east of the CWA by midnight Thursday morning. Cold air 
advection behind the front on northerly winds will reduce overnight 
lows to the mid 30s to 40s. 

Thursday will be dry but cooler as flow aloft becomes quasi-zonal 
and surface high pressure pushes in from the northwest. As the high 
moves into central Minnesota through the afternoon winds gradually 
change from northerly to east-southeasterly. Soundings indicate 
mixing will be shallow in the afternoon, only reaching up to around 
the 925 mb layer. Temperatures in the 925 mb layer have been 
trending slightly down over the past few model runs. In addition, 
lingering clouds may also limit surface heating. After collaboration 
with neighbors have opted to reduce NBM high temperatures a couple 
of degrees by blending it with CONSShort. Highs are now expected to 
climb into the 50s to mid 60s. 

Friday will be mostly dry as we watch the approach of a strong upper 
wave from the southwest. Highs will climb into the upper 50s and mid 
60s. Friday late afternoon into the evening the wave and surface low 
will begin producing showers and thunderstorms that will slowly move 
north to northeast through Friday night and most of Saturday. 
Saturday evening and most of Sunday will be dry with highs in the 
50s and 60s. Followed by another strong upper wave that will bring 
extended chances for rain into the first half of next week. Long 
range ensembles indicate a high probability (70-90%) of total rain 
equal to 1 inch or more from Friday evening through next 
Wednesday. Further details are vague at this point and there is 
much uncertainty with track and evolution of these waves.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 647 AM CDT Wed Oct 28 2026

Areas of fog and mainly IFR stratus (locally LIFR or MVFR) will 
continue to impact the area through this morning. Any fog should 
lift by the mid to late morning hours and cigs should slowly but 
surely lift throughout the day today. Stratus will also be eroding 
from west to east as a cold front sweeps through the area today into 
this evening. Fog is possible once again tonight/tomorrow morning, 
but low confidence in the extent of this round of fog preclude 
mention in the TAFs at this time. 

The aforementioned frontal passage will bring a wind shift with 
southerly winds turning northwesterly as the day progresses. The 
front will moving into central South Dakota by the late morning and 
exit into central Minnesota and central Iowa by the early evening. 
Ahead of the front, scattered showers will be possible across the 
area. A few thunderstorms may be embedded within this activity, but 
coverage is expected to be low. Thus, left thunder out of the TAFs 
at this time. The better chances for thunderstorms will be north of 
I-90 in far eastern South Dakota into southwest Minnesota.

&&

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

&&

$$

UPDATE...Samet
DISCUSSION...AJP
AVIATION...Samet