Marcus, Iowa Weather Forecast Discussion

518
FXUS63 KFSD 101743
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
1243 PM CDT Wed Sep 10 2025
.KEY MESSAGES...
- Canadian wildfire smoke will linger aloft through tonight. Any
  surface impact will be minimal.
- Temperatures warm to well above mid-September normals Thursday
  through Saturday.
- The next best chance for showers and thunderstorms (30-50
  percent) will be Saturday night through Sunday.
&&
.DISCUSSION...
Issued at 335 AM CDT Wed Sep 10 2025
Light winds and mostly clear skies have resulted in fairly
widespread dense fog across a good portion of the area early this
morning. Lowest visibilities currently reside from east central SD,
through southwest MN, and into portions of northwest IA, and the
current Dense Fog Advisory covers this well. Will continue to
monitor through the morning hours for possible expansion if
conditions deteriorate farther to the south/west. Look for any fog
that develops to burn off by mid to late morning.
Otherwise, the warming trend continues for today as an upper level
ridge oriented over the eastern Rockies nudges eastward through the
day. With that, highs will climb into the mid/upper 70s east to
lower/mid 80s west. There will be a little more breeziness today
west of Interstate 29, this in response to an increasing surface
pressure gradient and slightly higher winds aloft over that area.
Guidance continues to show Canadian wildfire smoke streaming over
the region at least into tonight, though it appears there will be a
lesser chance of smoke reaching the surface. Tonight will be a mild
night with lows in the mid 50s to lower 60s. With light winds east
of Interstate 29, may again see a risk of fog over that area.
Summertime heat slowly builds into the area for Thursday through
Saturday as the aforementioned upper level ridge moves from west to
east across the region through the period. 700/850 mb temperatures
will be in the top 10th percentile or greater with respect to NAEFS
climatology, and related to that highs will rise into the 80s for
Thursday, then 80s to lower 90s for Friday and Saturday. Rainfall
chances look to remain low (less than 20%) through the period.
Model guidance shows some consensus on an uptick in shower and
thunderstorm chances by Saturday night and Sunday as an upper level
trough over the western CONUS begins to shift into the Plains
states. There may be an increase in severe storm chances during this
period as shortwaves lift out of the trough on a southwesterly upper
level flow - but this will be dependent on placement of frontal
boundaries and how much moisture return is realized across our area.
Some risk of severe weather is supported by latest CIPS analogs.
Rainfall chances become even more uncertain by the beginning of next
week with model differences, though temperatures look to remain
above seasonal averages with highs in the mid to upper 80s.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1240 PM CDT Wed Sep 10 2025
Morning fog has dissipated, but some low stratus remains along with
some developing MVFR CU to start the period. These clouds should
gradually lift through the afternoon, leading to VFR conditions
area- wide this evening. More fog is expected to develop late
tonight into early tomorrow morning, though it is not expected
to be as dense as it was this morning at least at the TAF sites.
This is due to higher winds and some high cloud cover, but
visibilities could still drop to MVFR to IFR along and east of
I-29 especially around daybreak tomorrow. The best chance of
seeing dense fog with visibilities a quarter mile or lower will
be over southwest Minnesota. After fog lifts, VFR conditions are
expected to end the period.
Winds will be out of the east-southeast through this evening,
turning more southeasterly into tomorrow morning. Strongest gusts
through the period (20-25 kts) will be along and west of the James
River this afternoon, and then along and west of I-29 late tomorrow
morning.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...JM
AVIATION...Samet

NWS FSD Office Area Forecast Discussion