822
FXUS63 KFSD 051938
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
238 PM CDT Sun Oct 5 2025

.KEY MESSAGES...

- Elevated fire danger due to winds gusting 25-30 mph this afternoon.
  Minimum relative humidity values will be greater than 40%,
  but dry grasses and crops still have the potential to catch
  fire and spread rapidly.

- Light showers with some rumbles of thunder possible into the evening
  hours, mostly east of I-29. A second round of showers for
  Monday morning into the afternoon, mostly south of I-90.

- Near seasonable temperatures Monday, with a gradual warming trend
  through the rest of the week.

&&

.DISCUSSION...
Issued at 237 PM CDT Sun Oct 5 2025

Looking aloft at GOES upper-level water vapor we can see the wave
responsible for our showers today. At the surface a cold front will
continue to move slowly southeast through the region. As of 2 pm
CDT, a line of showers and thunderstorms is located east of Highway
60 in northwestern Iowa and southwestern Minnesota. These are
expected to intensify slightly and become more numerous as the cold
front moves through this area. This is in response to diurnal
heating and mid-level moisture influx increasing instability. Severe
weather is not expected, but dry low-level air may aid in
strengthening down draft gusts to around 50 mph. Storms move
southeast through the evening hours and should be clear of the area
after midnight tonight. Monday morning there is another chance for
showers and thunderstorms, mostly south of I-90, though a few may
drift farther north. Rainfall totals will be light, with just a few
hundredths possible.

Highs in general will be cooler today thanks to the cloud cover and
the northwesterly winds behind the front. Areas west of a line from
Yankton-Sioux Falls-Marshall will see the coolest highs in the mid
60s to mid 70s as you move from west to east. East of the line,
upper 70s to low 80s are expected. Grassland Fire Danger will once
again be elevated today thanks to gusty winds of 25-30 mph. Despite
minimum relative humidity values being well above critical (>40%),
with grasses and crops nearly cured (dry) any fires have the
potential to spread quickly. Please use caution with hot
machinery, sources of sparks, and report any fires immediately.

Tonight the cold front continues to push southeast of the region but
it`s progression slows significantly. There is some variation in
guidance, but for the most part the front looks to be out of the
region by around midnight tonight. Overnight lows will fall to mid
40s. Near sunrise Monday, a subtle wave works northeast through the
pattern resulting in weak 600 mb frontogenesis. This combined
with sufficient omega in the DGZ could result in another round
of light showers to storms. These storms are not expected to
become strong, as there is very little instability present. But
a few lightning strikes are possible. Area most likely to see
showers looks to be along and south of I-90, with the
possibility that a few showers may intrude a bit farther north.
Showers should taper off over the afternoon and evening. Again,
totals will be low, just a few hundredths to a tenth at most.
Highs for Monday will be about 5 or so degrees below seasonable
averages (Average is upper 60s), in the upper 50s to low 60s.
Lows will be around seasonal averages in the low 40s. Grassland
fire danger will be low, due to the cooler temperatures, higher
relative humidity values (40-55%) and northerly winds becoming
light.

Tuesday an upper ridge moves over the northern Plains with high
pressure at the surface. Conditions will be dry with light winds
becoming westerly to southwesterly. Highs will be around the
seasonal averages, in the upper 60s, with lows in the 40s. Wednesday
will also be dry with southerly winds increasing to 10-20 mph with
gusts 25-30 mph. Strongest winds are expected over central South
Dakota and will decrease as you head east. WAA in the midlevels will
help surface temperatures to climb into the low 70s with warm lows
in the 50s.

Wednesday night model guidance begins to diverge. The GFS has a mid-
level wave move sharply southeast through the region bringing
chances for rain Wednesday night through the day Thursday. The Euro
and Canadian indicate a much weaker wave, with only spotty chances
for rain. At this time range details are vague, but this potential
system will be monitored over the coming days.

Another upper ridge builds in for Friday and the weekend, with dry
conditions expected. WAA continues to warm the mid-levels with
soundings indicating good mixing through these layers. Surface
temperatures will warm into the mid to upper 70s for Thursday.
Friday just slightly cooler with highs in the low to upper 70s, with
Saturday and Sunday in the upper 70s to possibly some low 80s. Lows
Thursday through the weekend will be on the warm side, in the
50s.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 101 PM CDT Sun Oct 5 2025

A mix of VFR to MVFR ceilings as clouds stream in behind a cold
front that is currently draped roughly from Yankton, to Sioux Falls,
to Marshall. Clouds should thin this afternoon as dry air
entrainment occurs from above and below. Those that remain will
continue to trek southeastward.

Winds east of the front remain southeasterly, but will become
westerly to northwesterly as the front passes. Winds ahead of
the front are gusting to 20-30 kts. Winds will continue to gust
20-25 kts behind the front before gradually tapering off this
evening, becoming light and variable overnight.

There are currently showers and thunderstorms east of Highway 60 in
northwestern Iowa. These are expected to intensify slightly as the
cold front moves through this area, and diurnal heating and mid-
level moisture influx reduce stability this afternoon. Severe
weather is not expected, but dry low-level air may aid in
strengthening down draft gusts to around 50 mph. Storms move
southeast through the evening hours and should be clear of the
area after midnight tonight. Towards the end of the period there
is another chance for showers and thunderstorms, mostly south
of I-90. These should only impact KSUX.

&&

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

&&

$$

DISCUSSION...AJP
AVIATION...AJP