St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

923
FXUS63 KEAX 052252
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
552 PM CDT Sat Sep 5 2026

...Updated 00z Aviation...

.KEY MESSAGES...

- Hazardous heat continuing through the weekend and into parts  of
next week. An Extreme Heat Warning remains in effect  areawide until
8 PM Saturday and for counties generally along  and south of US-36
until Sunday at 8 PM. The Kansas City Metro  and surrounding
counties remains under an Extreme Heat   Warning until 8 PM Tuesday.

- Showers and storms will be possible (30-50% chance) Sunday
afternoon and evening. The highest chances are in northern  Missouri.

- Marginal Risk (Level 1 of 5) for severe storms capable of
  damaging wind gusts and hail.

&&

.DISCUSSION...
Issued at 327 PM CDT Sat Sep 5 2026

The Omega-block pattern will remain the focal point of the short-
term forecast with little changes to overall upper-level flow in the
last 24 hours or so. Peak heating is expected to resemble that of
yesterday given a lack of any other potential limiting factors. Just
before 9 AM Saturday, several sites across the region had already
started reporting heat index values in the upper 80s and lower 90s.
Given the fact that several sites were comfortably overachieving
forecast temperatures by 3-5 degrees this morning, afternoon
temperatures and highs were nudged up slightly. With temperatures
climbing into the upper 90s as we progress through the afternoon, we
could see widespread heat index values of 105F across much of
Missouri and far eastern Kansas. Some locations may be able to
surpass this 105F threshold, primarily those in our southernmost
counties where there`s a 60-80% chance of air temperatures hitting
or exceeding 100F.

With a backdoor cold front moving through overnight, temperatures
across northern Missouri are expected to top somewhere in the upper
80s (NE MO) or low/mid 90s (NW MO). This temperature reduction looks
to prevent widespread triple digit heat index values, and so the
Extreme Warning for these portions of the state will come to an end
around 8 PM today. Unfortunately, not all will be able to reap the
benefits of this "cold" front tomorrow as recent guidance has this
boundary coming to a halt generally north and west of the Missouri
River. As the day progresses, the front should begin to creep to the
southwest, but it doesn`t appear to be early enough to mitigate the
effects of diurnal heating. Temperatures in the mid/upper 90s are
currently forecast along and south of the I-70 corridor on Sunday,
but if the front is able to surge further south earlier in the day,
it could prevent these maximum temperatures from being realized.

Another consideration for Sunday is the potential for showers and
thunderstorms to develop in the afternoon and evening hours. Cooling
mid-level temperatures and steepening lapse rates ahead of the
boundary may permit scattered air-mass thunderstorm development in a
strong warm-air advection regime. Generally speaking, most storms
should be your run-of-the-mill ordinary thunderstorm, but forecast
soundings adopt a noteworthy inverted-V shape so downburst winds are
certainly not out of the question. It`s possible we could also see a
few stronger updrafts conducive of hail production but am not as
convinced on that threat as of yet. CAMs draw in additional
convection from the Northern Plains during the evening hours though
it`s unclear how this may evolve in our area with worsening
instability...current thinking is that any convection that does move
in from the north will rapidly lose intensity after sunset, though
strong wind gusts may be possible initially. SPC has highlighted
much of the CWA in a Marginal Risk (Level 1 of 5), encompassing both
of these possibilities. Overall, there`s about a 30-50% chance of
showers/storms across northern Missouri Sunday evening. Further
south and east, probabilities are lesser at around 20-30%.

The backdoor cold front will have completed its journey through the
CWA by Monday morning. This should result in somewhat cooler
conditions across the region, especially in central portions of
Missouri, hence the portion of the Extreme Heat Warning extending
from St. Joseph to Boonville will end at 8 PM on Sunday. A third
section of the Extreme Heat Warning that includes the Kansas City
Metro will be allowed to remain in effect until Tuesday evening at 8
PM. Conditions on Monday in the vicinity of the Kansas City Metro
and south appear borderline enough to warrant the continuation of
the warning for now, especially considering the widespread Major
(Level 3 of 4) and Extreme (Level 4 of 4) HeatRisk despite slightly
lesser temperatures and heat index values. Moreover, heat is
expected to recover on Tuesday, extending the already prolonged heat
event. Uncertainty still exists in regards to Wednesday as the
thermal ridge collapses and a low-pressure system marches along the
northern US border. This system will bring another cold front
through the region, but the timing of the frontal passage will
dictate whether heat headlines need to be extended through Wednesday
or not. As this frontal passage is better resolved in the guidance,
a decision will be made on whether an extension is necessary. To end
the week, expect closer to normal temperatures in the mid/upper 80s
and low 90s in addition to more shower and storm chances as
shortwaves snake through a more zonal pattern.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 549 PM CDT Sat Sep 5 2026

The diurnal cumulus will continue to dissipiate as we get past
sunset this evening. Any clouds that linger will have VFR bases.
Sunday afternoon, warm and moist airmass may result in shower
and thunderstorm activity after 20z. Given the scattered nature
of activity, will just place in PROB30 groups at STJ and the KC
Metro TAF sites for this issuance.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Extreme Heat Warning until 8 PM CDT Tuesday for MOZ028-029-037-
     043-053.
     Extreme Heat Warning until 8 PM CDT Sunday for MOZ020>022-030-
     031-038>040-044>046-054.
     Extreme Heat Warning until 8 PM CDT this evening for
     MOZ001>008-011>017-023>025-032-033.
KS...Extreme Heat Warning until 8 PM CDT Tuesday for KSZ025-057-060-
     103>105.
     Extreme Heat Warning until 8 PM CDT Sunday for KSZ102.

&&

$$

DISCUSSION...Macko
AVIATION...Krull