Marcus, Iowa Weather Forecast Discussion

989
FXUS63 KFSD 301144
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
644 AM CDT Tue Sep 30 2025
.KEY MESSAGES...
- Well above normal temperatures will continue into the upcoming
  weekend. A few record temperatures are possible again late
  this week.
- Dry conditions will dominate the remainder of the week.
  However, spotty late night-morning sprinkles will be possible
  through midweek. Rain chances remain less than 20%.
- Dry and occasionally breezy afternoons will lead to localized
  fire weather concerns as fire fuels continue to dry out. Use
  caution if working in fields or drier grasses.
- Next reasonable risk for widespread rain arrives at some point
  next weekend, with a cooldown in temperatures to finish the
  weekend. Highest rain probabilities are focused Saturday night
  into Sunday.
&&
.DISCUSSION...
Issued at 340 AM CDT Tue Sep 30 2025
TODAY-WEDNESDAY: The next couple of days will be dominated by
southwest flow in the mid-upper levels, between a prominent
ridge over the Great Lakes and a developing trough off the
Pacific Northwest coast. Occasional waves will slide over the
northern Plains, which at minimum will produce more abundant
cloud cover than we have seen in recent days. Forecast soundings
continue to show a dry layer below any mid level cloud deck, so
rainfall chances will be limited. However, weak instability at
times within the cloud layer may be enough to produce spotty
sprinkles.
Midweek temperatures will settle back a bit from our very warm
(localized record setting) highs of yesterday, but still well
above normal with lower-mid 80s common. Without full sunshine,
we may not see mixing as deep as recent sunny days, but with the
sub-cloud layer still rather dry, continued to hedge dew points
toward the NBM 10th percentile this afternoon, which yields
minimum humidity levels of 35-45 percent. This will keep fire
weather concerns at bay, but southerly winds gusting 25-35 MPH
in areas along/west of I-29 could still lead to locally elevated
fire danger where grasses or crops have sufficiently dried. Use
caution to avoid sparks if working in these dry fuels.
THURSDAY-FRIDAY: The upper ridge builds back to the southwest
across the southern Plains while the Pacific Northwest trough
slowly moves onshore and digs southward into the Great Basin and
western Rockies. Warmer temperatures return to the northern
Plains and 850mb temperatures topping 20C could again support a
few high temperatures around 90F or slightly higher. Current
record highs for this period are largely in the mid 90s, but an
anomalous record of 89F for Sioux Falls on Friday may be in
jeopardy. Perhaps a better chance of seeing a few record warm
low temperatures with breezy nighttime winds helping to hold
lows in the 60s.
With continued drying of crops/grasses and afternoon humidity
levels falling as low as 30-40%, breezier days could again lead
to areas of elevated fire danger during the latter part of the
week.
SATURDAY ONWARD: Models diverge a bit on placement/strength, but
general consensus shows the western trough swinging northeast
into the northern Plains this weekend. This should spread some
rain chances back into parts of the region. Latest ensembles
tend to favor rain chances to our west through north, though
confidence is currently low (20-30%) on timing/location given
aforementioned divergent model solutions at this range.
Greater confidence that this pattern shift will lead to cooler
(more seasonable) temperatures settling into the region by early
next week. Keep in mind that normal highs for early October are
in the upper 60s to around 70F, and our current stretch of
warmth is broadly 15-25F above these seasonal normals.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 644 AM CDT Tue Sep 30 2025
VFR conditions will prevail through the period, with broad mid
to upper level cloud cover generally at or above 8kft AGL. A few
sprinkles possible from the more extensive mid-level clouds, but
impacts would be limited and confidence is too low to include in
the TAFs.
Light/variable winds to start the period will settle around to
south and increase through the morning. Occasional gusts 20-30kt
this afternoon through sunset, strongest west of US Hwy 81.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...JH
AVIATION...JH

NWS FSD Office Area Forecast Discussion