Sioux Center, Iowa Weather Forecast Discussion

640
FXUS63 KFSD 061117
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
617 AM CDT Sat Sep 6 2025
.KEY MESSAGES...
- Some patchy frost and river and valley fog is possible this morning.
  Otherwise, partly cloudy skies and fall-like highs in the
  50-60s.
- Patchy frost is again possible Sunday morning with
  temperatures falling to the mid 30s to low 40s. Areas at
  elevation along the Buffalo Ridge are the most likely to see
  the lowest temperatures.
- Chances for isolated to scattered thunderstorms Monday. Some could
  be strong to severe.
- Additional chances for thunderstorms in the latter half of next
  week.
&&
.DISCUSSION...
Issued at 236 AM CDT Sat Sep 6 2025
TODAY: This morning we may see patchy areas of frost as low
temperatures fall into the mid to upper 30s. In addition, some
patchy areas of river and valley fog may form this morning. The rest
of today will be a lovely, fall-like day with partly sunny skies and
highs in the 60s. Aloft, weak moisture advection in the mid-levels
will allow for some diurnally driven afternoon cumulus to
develop, especially over southwestern Minnesota. Meanwhile, a
surface high pressure begins to push into the northern Plains
Saturday afternoon. Light, westerly winds will become
northwesterly and increase to 5-10 mph with peak afternoon
mixing. Gusts should be less than 20 mph, with the strongest
expected again over southwestern Minnesota. Overnight, winds
will become light and variable and skies will clear. High
potential for radiational cooling will allow lows to fall to the
mid 30s to low 40s. With this in mind, patchy frost may be
possible by early Sunday morning. Especially for areas at
elevation along the Buffalo Ridge. Those with tender outdoor
plants may want to cover them or bring them inside if possible.
In addition, patchy river and valley fog is also possible by
Sunday morning.
SUNDAY-MONDAY: High pressure slowly moves southeast through the
region Sunday, gradually turning winds southerly. Winds will be
slightly breezy at 5-10 mph with areas of central South Dakota
seeing up to 15 mph. A strong push of WAA will warm 850 mb
temperatures to 12-16 degrees C. Mixing this down to the surface
will see highs in the mid 60s over northwestern Minnesota, to the
low 70s elsewhere. WAA overnight will keep lows for Monday morning
warm, in the 50s.
A surface low will move into central South Dakota pushing a warm
front through our region late Sunday evening and into Monday
morning. Guidance is in low agreement on when and where moisture
will advect into the region ahead of the wave. Slower solutions
would indicate showers to be unlikely due to lack of moisture.
However, solutions that have moisture in place before the passage of
the front would align with 800-1200 J/kg of CAPE, around 25 kts of 0-
6 bulk shear, and an increasing low-level jet. This could support
isolated strong to marginally severe thunderstorms Monday morning.
Strong WAA behind the warm front will boost Monday afternoon highs
significantly, into the mid 70s to mid 80s. Continued moisture
advection on southerly winds will help to destabilize the
atmosphere throughout the afternoon. Elevated CAPE of 1500-2000
J/kg, with lapse rates of 7.0-7.5 deg C/km, and marginal bulk
shear of 25-30 kts may be enough to support isolated to
scattered strong to severe thunderstorms late Monday evening
into Tuesday morning. Confidence in severe storms is low at this
point due to two factors. One, a fairly strong cap will be in
place over much of the region. This could work to prevent
updrafts from forming. However, as the upper wave works through
the region that may provide enough forcing to break the cap. The
second factor is the low model agreement on strength, timing,
and track of the wave. However, enough of a risk exists to keep
thunderstorm chances in the forecast.
REST OF THE WEEK: Tuesday an upper ridge begins to push in from the
west, clearing showers out of the area by late Tuesday morning.
Highs will climb into the upper 70s to mid 80s. Wednesday looks to
remain dry with continued seasonably warm temperatures in the upper
70s to mid 80s. Storm chances return Wednesday evening as a ridge
rider wave works through the pattern. As the ridge begins to break
down Thursday into Friday additional chances for storms are
possible.
&&
.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 617 AM CDT Sat Sep 6 2025
Winds this morning are light and variable. Some patchy fog may
develop along rivers and valleys. Skies are mostly clear but some
clouds around 6000 ft AGL have begun to drift in from the northwest.
As the day continues, expect diurnally driven cumulus to continue to
develop. Despite the clouds, ceilings should remain VFR for the
entirety of the period. Clouds will dissipate as we lose
afternoon heating. In addition, winds will become northwesterly
late this morning as we begin to mix. Speeds of 5-10 kts
sustained with gusts around 20 kts are possible. Winds will
become light and variable again tonight.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...AJP
AVIATION...AJP

NWS FSD Office Area Forecast Discussion