Fairfax, South Dakota Weather Forecast Discussion

771
FXUS63 KFSD 051802
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
102 PM CDT Sun Oct 5 2025
.KEY MESSAGES...
- A cold front will pass through the area today, resulting in
  cooler high temperatures. Early morning light showers will
  give way to another round of showers late this afternoon and
  evening across mainly northwest Iowa. A few rumbles of thunder
  are possible.
- Elevated fire danger is possible today along and southeast of
  a Marshall, Minnesota to Sioux Falls, South Dakota, to
  Yankton, South Dakota line where humidity values will be
  lowest.
- Near seasonable temperatures return on Monday before highs
  slowly warm back to above average through the rest of the
  week.
&&
.DISCUSSION...
Issued at 339 AM CDT Sun Oct 5 2025
Light showers begin the day today as a cold front continues to push
through the forecast area early this morning. These showers have
been encountering drier air as they push eastwards. Some may survive
as they push eastwards with the front but should see coverage overall
decrease, especially as the better forcing for ascent pushes
northwest of the area. Breezy winds will persist through the morning
hours thanks to the cold advective push right behind the surface
front. Winds will turn westerly for the morning hours with gusts up
to 25-40 mph. Winds will be decreasing through the afternoon hours
as the front pushes southeast of the area while high temperatures
warm to the upper 60s to low 80s from northwest to southeast. That
said, elevated fire danger remains possible, mainly along and
southeast of a Marshall, Minnesota to Sioux Falls, South Dakota, to
Yankton, South Dakota line where humidity values will be lowest
around 30% thanks to dew points falling to the upper 40s to low 50s.
At the same time, this is the same area where winds will be weakest
with gusts weakening to just about 25 mph. While elevated fire
danger is still possible in this area, have decided to hold off on
issuing a Special Weather Statement (SPS) at this time given the
marginal fire danger conditions. At the same time, light showers may
develop across portions of northwest Iowa during the late afternoon
to early evening hours behind the main cold front. The bulk of the
showers and thunderstorms look to develop along to just barely ahead
of the front southeast of the area. With lingering instability
behind the front, could see a few rumbles of thunder in the light
showers that do develop. Showers across northwest Iowa should end by
about midnight. Mainly quiet conditions are expected through the
overnight hours with low temperatures falling to 40s. The exception
will be another round of showers developing across northern Nebraska
and southerly South Dakota just before daybreak tomorrow.
These showers will kick off the day on Monday as strong
frontogenesis (FGEN) takes place between 700-600 mb. The lift from
the front will cool the mid levels to saturation, especially in the
dendritic growth zone (DGZ). With sufficient omega in the DGZ, light
rain showers will persist along the Missouri River Valley and into
adjacent portions of northwest Iowa throughout the day on Monday.
With forcing for ascent slowly weakening throughout the day, only
light rainfall amounts are expected on the order of a few
hundredths. Cloud cover will blanket the area for the majority of
the day, keeping high temperatures near seasonable in the 60s across
the area. Low temperatures will fall to the 40s overnight.
Tuesday and Wednesday will be quiet days with high temperatures
slowly warming from the 60s on Tuesday to the low 70s on Wednesday
thanks to weak ridging aloft. Wind remain light on Tuesday but
strengthen again on Wednesday as the surface pressure gradient will
re-tighten, bringing breezy winds back to the area. This could
result in some elevated fire danger but the strongest winds look to
be offset from the lower humidity at this time. Lows will fall to
the 40s Tuesday night before warming back to the 40s and 50s
Wednesday night.
Temperatures remain in the 70s for Thursday and Friday but could
potentially see some very light rain on Thursday as a weak shortwave
trough passes through the Northern Plains. The ensembles are in
decent agreement as they show a broad 20-60% chance for exceeding a
mere hundredth of an inch, mainly on Thursday. Once the wave pushes
southeast of the area, Friday looks to be a more quiet day.
Uncertainty increases in the upper level patterns evolution for the
weekend. Medium range guidance shows a rather large trough pushing
into the Northern Plains. The ensembles paint a similar picture but
are slower with the upper trough. They also diverge in how the
trough evolves into next week with some ensembles developing a
cutoff low and others keep it as a progressive wave. Too early to
say what evolution will occur at this time but will monitor over the
next week. Otherwise, high temperatures will remain in the 70s.
&&
.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...Meyers
AVIATION...AJP

NWS FSD Office Area Forecast Discussion