St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

632
FXUS63 KEAX 051749
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
1249 PM CDT Wed Aug 5 2026

.KEY MESSAGES...

- Multiple Rounds of Showers and Thunderstorms Today Through
  Thursday Morning

- Flood Watch Issued for Central Missouri Tonight through Thursday
  Morning

- Brief Break from 90s Temperatures, But Warm Up Possible Over the
  Weekend Again

&&

.DISCUSSION...
Issued at 356 AM CDT Wed Aug 5 2026

Mid-level trough axis this morning is currently positioned across
the eastern Plains, and will continue to shift eastward with
additional digging toward the lower Missouri River Valley. Several
pockets of upper-level divergence has been providing extra lift
across much of the Upper Midwest and middle Mississippi River Valley
over the past 12-18 hours. Surface cyclone has continued to deepen
across parts of the Central and Southern Plains, with surface
troughing extending northeastward into northern Missouri. This area
of surface troughing is also where a stalled thermal boundary
currently sits. And overnight convection in eastern Nebraska,
northwest Missouri, and western Iowa has provided precipitation drag
on the cool side to further reinforce the temperature gradient
associated with it. This will set the stage for favorable forcing
Wednesday afternoon and evening for new development. For the
remainder of the morning, a few weak mid-level vort maxima are set
to track across the area, which may provide enough mid-level lift of
a warm and moisture boundary layer along and ahead of the frontal
boundary to generate some shower activity. 06z HRRR and other CAMs
have been keeping morning activity more in northern Missouri to
Central Iowa, where stronger surface convergence has been present
along the boundary this morning. This area has also seen few mid-
level disturbances that provided further lift, compared to areas
south of Hwy. 36 this morning. The NAMNest is the only model that
tries to generate stronger convection further south during the
morning hours, but current radar trends seem to support more of a
HRRR and even RRFS solution. Wind shear, especially with the low-
level jet could help organize convection this morning in our
northern zones, but the better kinematic support for that is
currently concentrated over Central Iowa. We will need to watch
rainfall rates if anything does move southward, especially in Adair
County MO and surrounding areas that saw locally heavy rainfall late
Tuesday evening.

Most of the redevelopment and threat for severe weather on Wednesday
afternoon and evening is going to heavily depend on seeing some
clearing, and having enough boundary layer destabilization to get
stronger storms going. We should see the surface cyclone move
slightly eastward, with surface troughing and associated pressure
falls moving further into the lower Missouri River Valley.
Differential heating potential along the boundary will also play a
role in convergence. Stronger theta-e advection this afternoon and
evening should help areas southeast of the thermal boundary reach
MUCAPE values between 1500-2000 J/kg. Some solutions that completely
clear out morning activity push SBCAPE values to  near 3500 J/kg.
Getting activity to initiate with plenty of low-level and even mid-
level kinematic support should not be a problem. And while
destabilization occurs and increasing CAPE values, lapse rates based
on model soundings on the warm side of the boundary are not overly
steep. Selecting a few points throughout the forecast area, we are
not seeing any lapse rates get much steeper than 6C/km. This may
end up being the limiting factor to getting stronger cores this
afternoon, despite 0-6km bulk shear values between 30-40 kts
(potentially nearing 50kt later Wednesday evening in Central MO).
While the kinematic parameters may initially look favorable for
supercell storm mode, the broadscale lift support by the approaching
500mb vort maxima may lead to interference, yielding widespread
multicells through the afternoon. As for storm evolution, there
looks to be 3 distinct rounds of convection initiation. The first is
already occurring this morning in Iowa and northern Missouri. The
potential for this to move southward across the rest of the forecast
area appears to dwindling, though there are few light radar returns
over central Kansas that will need to be monitored. After 18z today,
when there will be some destabilization (the magnitude of it will
largely depend on any cloud clearing if we are able to get some
subsidence after any more rain showers). Multiple CAM solutions
develop multi cells from eastern Kansas to Central Missouri. Based
on simulated radar reflectivity fields, the stronger cores between
18-22z this afternoon are closer to Central MO. And this may be
because those areas may be further removed from cloud cover that is
otherwise closer to the boundary, and perhaps larger surface
pressure fall drop through the afternoon. However, lapse rates from
soundings near the environment CI there are still not overly
impressive, and any cells that develop will have to tap into the
shear to organize. With the moisture that is present (PWATs ranging
between 1.75 to nearly 2.00 inches on the warm side of the
boundary), precipitation loading may be enough to create stronger
vertical pressure gradient perturbations that could lead to
localized downburst winds to around 60 MPH. Expect the KDP values
from dual-polarization to be quite high with large liquid water
content in these storms. This precipitation loading possibility may
extend westward into the KC metro, especially with forcing along the
boundary. However the thermodynamic environment may not as great.
Any activity that develops in the afternoon will have a battle
between favorable forcing and favorable thermodynamics.

Later in the evening after sunset, as the low-level jet starts to
ramp up (nearly 40kts in some CAM guidance), additional convergence
along the thermal boundary is likely to initiate, and this may
develop closer to the KC metro unless the boundary shifts eastward
or surface pressure fall trends drastically move toward eastern
Missouri. Lapse rates continue to very rather poor, but with theta-e
advection through the afternoon, overall instability should be
there. Thunderstorms in the evening are more likely to be elevated,
unless there is a dramatic modification to the boundary layer prior
to sunset. As the low-level jet kicks, the HRRR and RAP shows
impressive effective-inflow layer shear into thunderstorms that
develop, that will once again be able to help them organize.
However, given the the weaker lapse rates, it may take longer for
storms to congeal and organize before that reach potential severe
strength, and therefore, makes the severe threat more favorable for
areas east and southeast of KC metro even through this evening. Wind
gusts will continue to be the primary threat, with precipitation
loading helping to produce winds, even if the thunderstorm bases are
elevated. As the front then moves eastward through the night,
additional H5 short-wave perturbations may continue to provide lift
and post-frontal shower/storm activity through Thursday afternoon.
Most of the post-frontal activity, while it may still have access to
healthy moisture, will likely be lacking sufficient instability to
continue any kind of severe threat. However, if additional rainfall
activity falls over areas again, this may lead to hydrology issues.

A Flood Watch has been issued for central Missouri for Wednesday
evening through Thursday morning. The airmass ahead of the boundary
is characterized by PWATs between 1.75 and 2.00 inches, along with
warm cloud depths attempting to push about 4km, and skinny CAPE
thermal profiles (thanks to the weaker lapse rates). While it is
unclear if training storms along the boundary will become problem,
multiple rounds of showers even if a few hours apart could still
lead to rainfall rates between 1.5 to 2.0 inches per hour,
especially in central Missouri. 00z HREF mean QPF has between and 1
to 2 inches of rainfall east of Hwy. 65 tonight through Thursday
morning. Probability matched mean (PMM) values retain maximum
pockets exceeding 3", and other ensemble guidance depicts some
potential for as much as 3-5 inches of rainfall in Central Missouri
that could occur within a 3 hour period. This is the reason for
issuing the Flood Watch across Central Missouri. For areas further
west, heavy rainfall is still likely. However, rural areas that have
been dry should be able to handle a couple of inches of rainfall.
And with the signal in the HREF and other CAM guidance not being as
strong for exceeding 3 inches of QPF, did not draw the Flood Watch
back as far west with this initial issuance. If we see stronger
cores initiate this afternoon further west, and still expect evening
development along the low-level jet to bring more rainfall, westward
expansion may become possible. But as of right now, even maximum QPF
values from ensemble suites is not as threatening in our west as it
is in our eastern zones. As for the KC metro and flooding, the
overall QPF signal is for only  around 1.0 to 1.5 inches over the
event. However, if we get activity further west, and see this fall
within 60 to 90 minutes, we may see typical urban flooding issues
arise, including some of the flashy creeks streams in the metro.

A break from rain shower activity is expected Thursday Night into
early Friday, but another short-wave perturbation may bring more
rain back to parts of the forecast area. Ensemble trends though the
remainder of the weekend have backed off on rainfall potential,
compared to output from a few days ago. However, after the relief
from temperatures on Thursday, if the ridge over the western CONUS
continues to build, we may see strong WAA that helps to send
temperatures back into the 90s over the weekend, and that may
continue into the next work week.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1235 PM CDT Wed Aug 5 2026

Patchy showers continue across the region this early afternoon,
and will likely linger through mid to late afternoon. Additional
shower and thunderstorm development is likely by around 4z
Thursday, with periods of moderate to heavy rain and reduced VIS
possible along with MVFR CIGs. Rain should come to an end after
12z Thursday, with MVFR CIGs continuing through the remainder of
the morning hours.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch from 7 PM CDT this evening through Thursday
     morning for MOZ007-008-016-017-024-025-032-033-039-040-
     045-046.
KS...None.

&&

$$

DISCUSSION...Krull
AVIATION...BMW