St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

895
FXUS63 KEAX 050816
AFDEAX

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

.KEY MESSAGES...

- Hazardous / prolonged heat continues through the weekend and into
next week.

  - Extreme Heat Warning remains in effect through 8 PM Saturday area
    wide and through 8 PM Tuesday for areas along and south of
    a line from St. Joseph MO to Boonville MO

- Chances (20 to 35 percent) for thunderstorms Sunday afternoon
  and evening, with greatest chances tending to be over northern
  Missouri.

&&

.DISCUSSION...
Issued at 315 AM CDT Sat Sep 5 2026

The general pattern evolution across the CONUS remains high
confidence. The LREF 500mb spreads are predominantly < 3 dam across
CONUS until mid-week. Even then, majority of the increasing spreads
are understandably seen arcing over the Central and Southern Plains,
keeping area 500mb spreads <= 3 dam through next week. What does
this mean? Since we are currently entrenched within mid-level
ridging, it generally means well above normal temperatures stick
around through the forecast. For general reference, 30-year normal
highs are around the low to mid 80s this time of the year. Of
course, 500mb pattern evolution does not tell the whole story, and
there are some details within the forecast, aside from heat, worth
noting, including storm chances, backdoor cold front, and more
substantial relief later in the forecast.

The existing Omega block pattern is expected to largely remain
locked in place through the weekend. While this keeps peak heat
potential similar to previous few days, in the mid to upper 90s,
there will be an opportunity for that temperature forecast to bust
this weekend. Today will not be that day though with light southerly
flow and a 700 mb temp ridge nosing into the area that will keep any
air-mass convection from developing. Those chances should remain
relegated more toward the Ozarks portions of the state where 700mb
temps are a couple degrees cooler and may allow convective temps to
be achieved. So mid-upper 90s, even touching 100 possible, for much
of the area today. By the latter portions of today, a surface high
dropping into the Great Lakes region will begin to push a backdoor
cool front (generous wording there) into NE Missouri. This will do a
couple of things. Most notably it will drop Sunday highs into the
upper 80s and lower 90s for NE and E Missouri. Unfortunately it
tends to stall out as it pushes westward across the state, providing
limited or no relief to areas W and S of a line from around
Maryville MO to Columbia MO. This results in the end of the Extreme
Heat Warning for portions of N/NE Missouri Saturday evening, and
continuing further south through Tuesday. Concurrently, 700mb temps
will fall across the area, setting the table for the potential for
some scattered thunderstorm activity near the surface boundary and
westward where this cooling may allow scattered air-mass convection
to be achieved. Additionally, shower/storm activity rounding the mid-
level ridge may drop S/SE out of Nebraska/Iowa along the expected
CAPE axis. Timing for all of this would be Sunday afternoon and into
the evening. Wind profiles do not support organization, but a very
dry sub-cloudbase layer could provide opportunities for evaporatively
enhanced downdrafts. As hinted earlier, this too provides the chance
for a busted temperature forecast in areas that see storms,
especially if areal coverage of activity increases.

By late weekend and into the early work week, the Omega Block begins
to break down in response to a Polar Stream trough pushing the New
England cutoff low eastward. The western CONUS cutoff low will take
advantage and begin to move E/NE itself, eventually yielding surface
low development over eastern Montana and into the southern Canadian
Plains. This will also act to push the mid-level ridge back eastward
and generally begin to flatten. Unfortunately, no notable relief to
the area, in fact a general brief resurgence of the heat as the
850mb temp ridge axis angles into the state. Expect temperatures
Monday to be similar to Sunday, but surge back warmer a few degrees
on Tuesday back into the upper 90s and around 100 for many. By
Wednesday, the mid-level ridge flattens and a cold front will begin
to approach the area from the north. This too is where uncertainty
begins to increase with some varied timing in arrival time. Slower
arrival may yield an extension of the Extreme Heat Warning one more
day, but confidence is not quite there to extend with LREF and NBM
MaxT spreads of 6 to 10 degrees. Higher confidence in relief (but
likely still at least a few degrees above normal) by Thursday and to
end the week though, including potential for some shower/storm
activity in/around the front as well as shortwave activity.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1153 PM CDT Fri Sep 4 2026

VFR conditions through the period. Light southerly winds are
expected to become more easterly after 06/0000Z.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Extreme Heat Warning until 8 PM CDT Tuesday for MOZ020>022-
     028>031-037>040-043>046-053-054.
     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-
     102>105.

&&

$$

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