Brookings, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

638
FXUS63 KFSD 190152
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
852 PM CDT Thu Jun 18 2026

.KEY MESSAGES...

- Isolated showers are possible (10-20% chance) over southwest
  Minnesota Friday afternoon. Wind gusts of 40 to 50 mph can`t
  be ruled out with this activity.

- More widespread rain risks return late Saturday into Sunday,
  though considerable uncertainty remains on the track of this
  system.

- Greatest severe weather risks continue to remain focused
  south of the Missouri River and Highway 20 corridor Saturday.

- Forecast rainfall totals vary significantly through Sunday,
  though greatest potential for excessive rainfall remains just
  south of the forecast area. Ensemble probabilities for >1.0"
  are around 20-40% near the Missouri River.

&&

.UPDATE...
Issued at 846 PM CDT Thu Jun 18 2026

As the last shower over northern Iowa fades, a dry evening is
in store for the area. Clouds over the northern High Plains will
drift into the area through the overnight hours from west to
east. Though winds turn light to calm overnight, these
increasing clouds should keep fog development at a minimum. The
exception is over parts of northwest Iowa mainly near and east
of a Spencer to Storm Lake line where the clouds don`t arrive
until sunrise or slightly afterwards. This is where the better
chances for fog reside, though probabilities are still quite low
at around a 20-30% chance at this time. Another cool June night
is ahead with lows in the low to mid 50s along the Missouri
River Valley to the upper 40s to low 50s elsewhere.

The forecast for tomorrow remains largely on track, see discussion
below for more details. One thing to note is that the chance for the
diurnally driven, potentially gusty showers tomorrow afternoon
have trended mostly east of the area into central and
southeastern Minnesota with the latest guidance, but still can`t
be ruled out over parts of southwest Minnesota (10-20% chance).

&&

.DISCUSSION...
Issued at 1247 PM CDT Thu Jun 18 2026

Still indications of some weak instability this afternoon, mainly
over parts of southwest MN. This could generate a few showers, of
which some gusty winds to 40 to 50 mph will be possible. This
activity will be driven mainly by the heat of the day so should
dissipate by about 9-10 pm.

A weak wave moves through Friday morning into the afternoon. The
combination of a modest increase in moisture in the mid levels with
weak instability above this moist layer, 700-500mb lapse rates about
7 degrees C, should allow for some ACCAS and showery activity during
this time. If the clouds and mid level moisture can exit by mid
afternoon, isolated diurnally driven showers may also pop up late
afternoon into the evening. Impacts from this will be minor, but
once again some gusty winds will be possible if some diurnally
driven showers can develop with fairly unidirectional winds with
height and fairly strong winds aloft.

Surface high pressure settles in Friday night into Saturday morning,
which could result in a little patchy fog.The better chances look to
be near the Big Sioux River Valley, but confidence is too low to
include in the forecast.

Saturday should be a fairly pleasant day with increasing clouds and
a fairly light easterly wind. Continued low humidity and highs
mostly in the 70s.

Upper level low pressure rocks northward later Saturday night into
Sunday morning. This lift will continue to fight the lower level dry
air, but especially south of I-90 rain and very isolated
thunderstorms will increase. With more confidence in this dry
layer, rainfall amounts have trended downward.

Sunday into Monday poses more problems as the models disagree
on handling the low pressure exiting. Rain chances should linger
Sunday into Monday but confidence on where and especially
amounts is very low.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 635 PM CDT Thu Jun 18 2026

Isolated showers that are located mainly north of I-90 to start
the period will gradually diminish through the evening hours. Mid to
high level clouds will gradually spread through the area from west
to east as winds turn light to calm overnight. This increasing cloud
cover should prevent most areas from seeing fog overnight, but can`t
rule out some patchy fog mainly near and east of a KSPW to KSLB line
where clouds arrive last early Friday morning. Chances for this are
low, around 20-30%.

Light showers also look to develop heading into Friday morning,
but VFR conditions are expected to continue through the end of
the period. Some thunder will be possible Friday afternoon
mainly in southwest Minnesota and adjacent portions of northwest
Iowa. Winds will increase from the west-northwest through the
day Friday. Afternoon winds on Friday will gust to near 30 kts,
highest over the higher elevations of the Coteau des Prairies.

&&

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

&&

$$

UPDATE...Samet
DISCUSSION...08
AVIATION...Samet