St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

101
FXUS63 KEAX 231727
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
1227 PM CDT Thu Jul 23 2026

.KEY MESSAGES...

- 30-50% rain chances this morning along and west of I-49/I-29
  as the decaying remnants of showers in the Central Plains push
  into eastern Kansas and western Missouri.

- Widespread measurable rainfall expected late tonight into
  Friday, with accumulations up to an inch in most locations.
  Localized corridors up to 2-4" will be possible, which would
  increase flash flood concerns for these locations.

- Temperatures return to the upper 90s this weekend, with 100+
  degree heat indices making a comeback as well.

&&

.DISCUSSION...
Issued at 1221 AM CDT Thu Jul 23 2026

Current Conditions & Synoptic Overview:

At the surface, high pressure has built across the Midwest, with
ridging aloft across the western US and troughing along the East
Coast. The northeast quadrant of the ridge aloft is being
suppressed by a shortwave trough ejecting across the High
Plains, and this shortwave is the forcing mechanism for a
cluster of showers across southwest Nebraska and northwest
Kansas early this morning, as well as a narrow line of weak
radar echoes ahead of the shortwave across southeast Nebraska
and into northwest Missouri.


Rain Chances Today and Tonight:

As the high pressure slides east, surface and low-level winds
turn southeasterly across our area today. The shortwave is
progged to continue slowly moving across Kansas and Nebraska
through the day today. A leading vort max ahead of the shortwave
moves across west-central Missouri this morning, bringing
15-50% chances of showers with it as activity moves from Kansas
into western Missouri. Coverage appears to become increasingly
scattered with this activity as it progresses further east and
south, so many areas will likely stay dry, especially the
northeast portions of the forecast area.

850mb dew points increase gradually through the day, but
sounding analysis indicates that much of the area will still
have a fairly deep layer of dry air to overcome before precip
reaches the ground. This decreases confidence that areas with
showers visible on radar will see rain down at the surface this
morning into this afternoon, with virga potentially dominating
for most of the day. There is little to no instability available
to help deepen the convection, so precip is expected to fall as
light showers today, with an isolated rumble of thunder possible
in the far southern portion of the CWA. HREF/REFS mean QPF
aligns with these expectations, with a very light QPF footprint
confined to areas generally along and west of I-49/I-29.

Sounding profiles begin to moisten by this evening, when
isentropic ascent begins increasing and another leading vort max
pushes into the area ahead of the shortwave. Showery activity
is expected to develop in northern Missouri along the narrow
dCVA axis this evening due to the enhanced forcing, but the main
show for rainfall won`t begin until late tonight into Friday
morning.


Heavy Rainfall Potential Late Tonight Into Friday:

Lee cyclogenesis in the Plains intensifies tonight, lifting a
warm front north along the 30kt nocturnal LLJ into southern
Missouri by Friday morning. Moisture advection intensifies with
the LLJ as well, exceeding 2.25" PW values by daybreak on
Friday. The main precip shield/MCS develops in eastern Kansas
after midnight, with most guidance suggesting the complex
reaches the western edge of the forecast area between 3AM-6AM
Friday. Initially, the complex should move more of a west-east
direction as rain develops along the nose of the LLJ, but
movement is expected to pivot to move more northwest-southeast
through the morning and into the afternoon as the shortwave
sags southeast through the day. The isentropic ascent is
strongest around and just after 12Z Friday, when convection is
expected to be strongest and most widespread.

There are varying signals for how Friday may evolve. High-res
guidance suggests the system will generally be progressive, but
may see redevelopment behind the initial rain shield.
Generally, rain will be primarily driven by isentropic ascent
rather than pure convective processes, so stratiform rain
processes will likely dominate for much of the event.
Instability is meager (<500 J/kg), so there will likely be a
few embedded rumbles of thunder and corridors of deeper towers
with more efficient convective rain rates at times, but
overall heavy rainfall and flooding threats are expected to
remain localized to the narrow corridors of deep convection
where rates can exceed 1.5-2" per hour. It may not be a complete
all-day washout in all areas, but most should expect rain
through the morning hours and then at least on-and-off through
the afternoon and into the evening.

High-res ensembles also suggest that widespread accumulations
will be measurable but not overly impressive or concerning,
with most areas getting less than an inch of rain. However, HREF
and REFS LPMMs do show a few highly localized swaths of
accumulations up to 5" where that deep convection occurs, which
would be reasonable to expect within such a moist environment.


Temperatures Climb This Weekend:

Rain and the associated cloud cover will help to limit
temperatures today and tomorrow, so highs have been dropped a
few degrees accordingly, with highs in the upper 70s to low 80s.
The ridge aloft recovers from the shortwave intrusion and
re-strengthens, with southwesterly low-level flow once again
advecting hot air back into the region. Hot and humid conditions
settle back into the area Saturday-Monday, with temperatures in
the upper 90s and dew points in the low to mid-70s. This brings
us back to heat indices in the 100-110 degree range, which means
a Heat Advisory may become necessary before too much longer.


Next Round of Rain Chances Sunday/Monday:

While there is still considerable uncertainty in the location
and details of features beyond Saturday, guidance does indicate
that a favorable setup for severe weather to our north in Iowa
on Sunday, when another shortwave may impinge on the northeast
quadrant of the ridge and increase rain chances. Current NBM
PoPs do not tell this story well, and the current SPC Day 4 15%
Risk remains confined to the Upper Midwest, but machine learning
guidance pulls an area of 15-30% severe weather probabilities as
far south as northern Missouri on Sunday, so it`s possible we
get clipped in our north by the MCS remnants from areas further
north. Considering the hot and humid air mass that will be in
place, if forcing shifts slightly further south, the environment
would certainly support thunderstorms, so we will continue to
monitor future guidance suites for potential southward shifts.
The other thing this system could do is increase cloud cover on
Monday, which would be beneficial in reducing temperatures.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1225 PM CDT Thu Jul 23 2026

VFR conditions prevailing for the remainder of the day today.
Presently, some -SHRA persists to the west of terminals from
this morning. Have left in a PROB30 group through 20z to account
for remnant showers as they gradually dissipate through the day.
Else, expecting the next significant impact to terminals
overnight into tomorrow morning with a weather system entering
from the west around 9z. Guidance has been variable with the
onset of weather with this system, but confidence is still
present in weather impacting all terminals through the remainder
of the forecast period. Guidance also indicates lowering
ceilings/visibilities with the system, so have included a line
of approximate timing for MVFR ceilings and lowering
visibilities with heavier rainfall.

&&

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

&&

$$

DISCUSSION...Camden
AVIATION...SPG