168
FXUS63 KSGF 181905
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
Issued by National Weather Service St Louis MO
205 PM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Thunderstorms are expected overnight tonight with the focus
  across central Missouri. A few storms could be severe with
  damaging winds the primary threat.

- Another round of thunderstorms is possible Wednesday evening,
  this time with the focus across southern Missouri. Damaging
  winds and heavy rainfall will be the primary threats.

- Hot and humid conditions continue to the south of a cold front
  on Wednesday with southwest Missouri having the best chance
  (50%) of seeing heat index values near 105 again.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 200 PM CDT Tue Aug 18 2026

An upper level ridge is reorganizing over the Southwest US while
a trough is passing through the Upper Midwest pushing east
toward New England in the coming days. At the surface, high
pressure currently over the lower Ohio Valley will push east
toward the southern Appalachians, with a moist southerly flow
through the Southern Plains and into the Ozarks. It`s this
southerly flow beneath the influence of the ridge that has led
to another day of hot weather in southwest Missouri and eastern
Kansas. Looking to the north, the remnants of a convective
complex that moved into northwest Missouri this morning
continues to dissipate as it heads east. However, redevelopment
is expected this evening across northeast Kansas and northwest
Missouri where the convective outflow intersects with an
increasing low level jet. The developing storms would then track
ESE primarily through central Missouri overnight. Initiation is
expected around 9 or 10PM with storms not likely in our forecast
area until between midnight and 6AM. With the warm, moist air
mass feeding these storms and modest wind shear available,
convective clusters capable of damaging winds will be possible.
In addition, heavy rain rates of 1 to 2 inches per hour can be
expected, though the focus for persistent rainfall at the moment
remains just to our north closer to I-70.

Convection wanes Wednesday morning, though convective outflow
pushes an effective cold front southward through the region.
This will shove the hot and humid air mass further southwest for
Wednesday, with the primary forecast uncertainty hinging on
where that boundary lands. South of the front another hot and
humid day is expected, with heat index values approaching 105,
but north of the front it will be considerably cooler,
potentially only in the 80s with cloud cover. NBM interquartile
range for high temperatures on Wednesday is from 8 to 10
degrees, rather large for a Day 1 forecast this time of year.
This reflects the uncertainty on that frontal position which
will be determined by the track of convection tonight and the
intensity of the push southward of the outflow. Southwest
Missouri has the best chance (50%) of seeing another day of heat
index values near 105, though confidence is not quite high
enough to extend the Heat Advisory just yet.

Another round of convection is expected to fire in the vicinity
of the boundary Wednesday evening. At this time the boundary is
likely to be across far southern Missouri near the Arkansas
border. Storms forming here will have access to the hot, humid,
unstable air mass south of the front and moderately strong wind
shear. Supercells and convective clusters will both be
possible, with damaging winds and heavy rainfall the primary
threats and hail or a tornado as secondary threats. These
storms are expected to push south into Arkansas by around
midnight Wednesday night as the front gets a better push
southward behind the upper trough moving through the Great
Lakes.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 200 PM CDT Tue Aug 18 2026

The story in the long range forecast will be the battle between
cool air masses pouring out of Canada beneath a trough in the
Eastern US and hot conditions building beneath the ridge over
the Southwest US. Our forecast area will frequently be at the
boundary of these two air masses, with heat building to the west
while cooler air hangs on to the east beneath northwesterly
flow aloft. There will also be occasional chances for
thunderstorms as impulses rotate around the ridge, but limited
moisture flowing north through the Plains will limit how
frequent or widespread these convective complexes may be. Latest
NBM PoP remains quite low (20 percent or less) through the
extended forecast, but Low Resolution Ensemble guidance does
show 30 to 50 percent probability of measurable rainfall in any
24 hour period through this weekend, indicating greater
confidence that some storms will be around but timing and
location uncertainty is keeping the PoP lower.

Confidence is greatest in cooler conditions Thursday into
Friday, with NBM high temperature interquartile range of 5
degrees or less. However, uncertainty increases for the weekend
with that same interquartile range rising to 10 degrees or more
Sunday and Monday. If we stay more under the influence of the
cooler air masses, temperatures will tend to top out in the 80s,
but if the hotter air from the ridge noses in, then we will see
temperatures approach 100 degrees again. Current NBM forecast is
a blend which does reflect a rather large gradient, hotter in
the west and cooler in the east.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1219 PM CDT Tue Aug 18 2026

VFR conditions will continue at the TAF sites tonight into
tomorrow. A complex of thunderstorms is expected to form and
pass by to the north tonight, but is unlikely to impact any of
the terminals locally. There`s an outside chance of a shower
during the day Wednesday, but confidence is too low to include
in the TAF at this stage. Some minor low level wind shear is
likely tonight at JLN and BBG as southwesterly flow picks up
aloft over the top of light SSE surface flow. This decreases in
the morning as winds aloft ramp down and surface winds turn back
southwesterly with deeper mixing.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
KS...None.
MO...None.

&&

$$

SHORT TERM...
LONG TERM...
AVIATION...