St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

806
FXUS63 KEAX 081123
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
623 AM CDT Tue Sep 8 2026

...12z Aviation Update...

.KEY MESSAGES...

- Dangerous heat will see a brief resurgence today for most
  locations, and potentially into Wednesday for areas south of
  the Missouri River.

- A few strong to severe storms are possible this evening into
  the overnight hours, mainly across northern Missouri. And
  again Wednesday afternoon to evening, mainly south of I-70.

- Cooler/ more seasonal temperatures move into the area for the
  later half of the week and through the weekend.

&&

.DISCUSSION...
Issued at 356 AM CDT Tue Sep 8 2026

Change is afoot ... but the change that most probably want is still
a day away. Instead, today will be highlighted by a brief resurgence
of heat across much of the area. As the remnant Omega Block that
helped yield the prolonged heat continues to break down, the mid-
level low lifting into the Canadian Plains will push the mid-
level/500mb ridge back overhead and with it the 850mb thermal ridge.
Additionally, winds will shift back more southerly, helping lift a
plume of moisture/higher dew points into the area.  All of that will
yield highs jumping back into the mid 90s to around 100 and heat
index values toward 105 or greater in many locations. Given some
displacement between highest temps and highest dew points, this
tends to result in similar forecast heat index values for a majority
of the CWA. The exception may be the far NE, such as Kirksville,
where both peak heat and peak humidity may not quite make it. This
also results in both continued and renewed heat headlines. SW areas,
including the KC Metro counties, remain in an Extreme Heat Warning
given the prolonged duration they have experienced. Areas to the
N/NE/E, to a line from roughly Bethany to Columbia, will have a Heat
Advisory in place. At this time, all heat headlines expire this
evening, but there remains the potential for far southern counties
of the CWA to be extended into Wednesday, all dependent on frontal
progression. Fairly significant uncertainty remains in that regard,
as seen in NBM probabilities of MaxT >= 95 and LREF probabilities of
ApparentT > 100 on Wednesday. In both cases, both struggle to depict
probabilities > 70 percent. Collaboration with SGF/LSX yielded the
decision to hold off on Wednesday at this time, as hinted above. The
noted trend within NBM and LREF probabilities has been a tad slower
frontal progression, reflected in bit higher probabilities vs 24 hrs
ago.

As the aforementioned front drops toward and through the area, so
too associated showers and storms. The strong to severe threat
remains on the lower overall in the traditional, organized, sense
for the area with supportive deep layer shear remaining displaced
well north. There should be modest MUCAPE values ahead of the front
later today, but the question becomes just when first storms may
enter NW/N Missouri. Should the suggested slower frontal progression
trend prevail, storms may not arrive until around/after 06z. This
would tend to limit the severe threat as MUCAPE subsides and
activity becomes elevated. Will note though that dry low-levels will
be in place and evaporatively enhanced down drafts / downbursts
could yet be possible with any of the more robust initial updrafts.
Generally expect more a general shower / isolated thunder threat at
the moment though. No issues with the new SPC Day 1 Marginal Risk
over the far NW/N.

Into Wednesday, frontal progress is the key. Aside from the already
discussed heat, it too would dictate location of any strong/severe
storm threats Wednesday afternoon/evening. The new SPC Day 2 Outlook
has expanded the Marginal Risk northward vs the old Day 3 Outlook,
also suggesting a slower frontal passage trend. Overall, environment
ahead of the front Wednesday will be similar to that on Tuesday,
aside from being further south. At least modest MUCAPE >1500 J/kg is
likely, but looks to continue to lack overall supportive deep layer
shear. The resulting main risk would be strong and damaging winds
given the dry low levels / inverted-V model soundings. There may be
a small window for hail as well, dependent on just how much
instability is able build in ahead of the front and if a bit better
shear environment can develop.

By Thursday, widespread relief behind the frontal passage, finally
putting an end to the incessant heat discussions of late. Much
welcome highs in the low to mid 80s across the entirety of the area.
And 80s largely forecast through the weekend. The next opportunity
for precipitation may move through Saturday as deterministic
synoptic models depict another frontal boundary dropping through the
Northern and Central Plains from a surface low lifting northward
through Minnesota and into Ontario.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 617 AM CDT Tue Sep 8 2026

VFR conditions to prevail through the TAF period across the
sites. KSTJ could be the lone exception with the potential for
showers/storms moving into its area toward the very end of the
new TAF period. Even so, ceilings should remain VFR, so would
need to be driven by rainfall driven visibility reductions.
Otherwise, S winds become more SW during the daytime, including
sustained around 10 to 15 kts and occasional gusts into the
teens kts. Depending on frontal timing, winds may shift more
northerly late in the period or just after, among the KC Metro
trio of sites.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Extreme Heat Warning until 8 PM CDT this evening for MOZ028-
     029-037-043-053.
     Heat Advisory from noon today to 8 PM CDT this evening for
     MOZ001>005-011>015-020>023-030>032-038>040-044>046-054.
KS...Extreme Heat Warning until 8 PM CDT this evening for KSZ025-
     057-060-103>105.
     Heat Advisory from noon today to 8 PM CDT this evening for
     KSZ102.

&&

$$

DISCUSSION...Curtis
SHORT TERM...
LONG TERM...
AVIATION...Curtis