268
FXUS63 KFSD 170900
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
400 AM CDT Fri Jul 17 2026

.KEY MESSAGES...

- Hot conditions will continue this afternoon and again Sunday
  where heat indices could climb to around 100, especially west
  of Highway 81. Saturday should see a slight break from the
  heat as winds turn northerly behind a weak front.

- Very patchy morning valley fog is possible daily, but
  widespread dense fog remains unlikely. Fog could reduce
  visibility below two miles at times.

- Wildfire smoke will return over the weekend. While lower
  surface concentrations are expected, any sensitive groups
  should begin to monitor their local air quality.

- Precipitation is very unlikely (less than 10%) through
  Saturday night. Isolated to scattered shower and storm chances
  return Sunday evening and night, but confidence is low on
  details.

&&

.UPDATE...
Issued at 356 AM CDT Fri Jul 17 2026

Taking a look across the area this morning, mostly clear and quiet
conditions persist. Similar the last few days, a few patchy spots of
areas of valley fog have developed this morning mainly due to
lighter winds and linger low level moisture. While this fog won`t
likely hang around long, there could be some temporary visibility
reductions through mid-morning so make sure to drive with care.
Otherwise, the focus continues to be on the heat today. Similar to
the past few days, highs will likely peak in the low to upper 90s
with the warmest conditions slightly offset from the highest dew
points. However, with a southwesterly wind in place and weak warm
air advection aloft (WAA); we could get just enough of a push to
break into low 100 degree heat index values across parts of the area
this afternoon. With this in mind, went ahead and issued an area-
wide heat advisory from 1 pm to 9 pm so make sure to stay hydrated!
Lastly, a cold front will progress through the area this afternoon
and evening. While this could potentially lead to few spotty showers
mainly along the Highway-14 corridor, not expecting any stronger
activity at this time.

&&

.DISCUSSION...
Issued at 1247 PM CDT Thu Jul 16 2026

Upper level flow goes through a touch of a transition Friday into
early next week. The first will be a glancing blow from some
stronger northwest flow aloft that drops south through northern MN.
This will bring a weak front into the area Friday night into
Saturday. Ahead of this front temperatures should warm quite a bit
with some enhanced mixing as surface winds turn a bit southwest.
This should lead to highs more widespread in the mid and upper 90s.
With dew points expected to be in the 60s, heat indices in the
afternoon could approach 100 degrees.

By Friday night winds will turn more northerly which will allow for
a bit of a break from the heat for many. Highs will likely range
from the mid 80s in southwest MN to the mid 90s closer to the
Missouri River.

As the next wave approaches the Canadian border Sunday, surface
winds will turn southerly and bring hotter temperatures back to the
area. The hottest will be west of I-29 while east of I-29 the return
flow will be slower to set up. The combination of temperatures and
humidity may push heat indices above 100 near and west of highway 81.

Ahead of this wave later Saturday night into Sunday morning some mid
level moisture and weak instability may allow for some ACCAS
showers/very isolated thunder. Will have to watch trends through the
day Sunday as this mid level moisture could linger and bring some
enhanced cumulus and spotty showers throughout the day. Very low
confidence in this right now however.

As this wave moves through ND into MN Sunday night another front
will sag south and may have enough forcing, instability and moisture
to allow isolated to scattered showers and storms to develop, mainly
north of I-90. Confidence remains a bit low, but an isolated severe
storm will be possible.

Monday is a tough call on temperatures and precipitation chances.
Model agreement on surface frontal position not real high and this
will play a decent role in how hot it gets. Monday could be another
day with heat indices above 100, especially south of I-90. Will be a
bit of a wait and see, especially considering how temperatures have
been coming up short of expectations for several days now.

Tuesday into Thursday should see spotty chances for showers and
storms with near to a bit below normal temperatures, generally
highs in the 80s and lows in the upper 50s to mid 60s.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1221 AM CDT Fri Jul 17 2026

VFR conditions are expected to prevail this period, with clear skies
and winds that are light and variable. Friday after sunrise winds
become southerly around 10 kts.  By mid-day a cold front will
approach KHON and progress through the region to the southeast.
Behind the front winds become northerly and gusts increase to 15 kts.

Friday afternoon as the cold front advances there is a low chance
(15%) for light showers and isolated thunderstorms. Severe weather
is not anticipated. Storms look to remain north of I-90 and into
southwest Minnesota by evening. Showers end near the end of the
period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from 1 PM this afternoon to 9 PM CDT this
     evening for SDZ038>040-050-052>071.
MN...Heat Advisory from 1 PM this afternoon to 9 PM CDT this
     evening for MNZ071-072-080-081-089-090-097-098.
IA...Heat Advisory from 1 PM this afternoon to 9 PM CDT this
     evening for IAZ001>003-012>014-020>022-031-032.
NE...Heat Advisory from 1 PM this afternoon to 9 PM CDT this
     evening for NEZ013-014.

&&

$$

UPDATE...05/Meyers/AJP
DISCUSSION...08
AVIATION...AJP