St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

468
FXUS63 KEAX 190808
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
308 AM CDT Sat Sep 19 2026

.KEY MESSAGES...

- Hot and Humid Saturday Afternoon

- Thunderstorms This Evening through Overnight; Some Severe Storms
Possible

- Cooler After Sunday

&&

.DISCUSSION...
Issued at 308 AM CDT Sat Sep 19 2026

The trough over the Intermountain West will send a few vort maxima
into the Central CONUS as we head into Saturday, which will provide
gradual H5 height falls across the area. The dCVA associated with
this will continue to deepen a surface cyclone which is beginning to
expand eastward, with surface pressure falls currently reaching into
eastern Kansas and eastern Nebraska. The warm front that moved
through today made into the far northeastern zones of the forecast
area, and extends into northwest Iowa, while the cold front trailing
this system is currently positioned from roughly Omaha, Nebraska
southwestward toward Colby, Kansas as of 08z this morning. Radar
early this morning is starting to show activity in southeast
Nebraska and northwest Missouri near the Triple Point, co-located
with an area of upper-level divergence. Off and on rain showers and
perhaps some scattered thunderstorms will develop as the day
progresses through early afternoon, but should remain mostly sub-
severe in our forecast area. Continued low-level southerly flow will
provide WAA keeping air temperatures in the mid 90s today, with
dewpoints reaching the upper 60s to lower 70s. The main focus for
strong thunderstorm activity is favored after 23z this evening,
mainly along the cold front as the primary forcing mechanism. Ahead
of the cold front, most of the eastern Plains and lower Missouri
River Valley will have plenty of daytime insolation that will work
to destabilize the boundary layer. As the main short-wave trough
moves overhead, mid-level cooling will promote steeper mid-level
lapse rates that will pave the path for stronger updrafts,
especially as this sits on top of warm moist boundary layer. As the
primary short-wave trough axis moves through, stronger mid-level jet
streak should help to provide increasing deep layer shear, with 0-
6km bulk values around 30-35 kts, and some deterministic guidance
does show this overspreading parts of the warm sector and extends
behind the cold front. This solution is a bit further east than what
previous numerical model guidance was suggesting the past couple of
days. Based on 00z HREF guidance, the warm sector appears capable of
SBCAPE above 1500 J/kg across much of the forecast, with a
concentrated axis of near 2500 J/kg from near Emporia KS northeast
toward south-central Iowa, just clipping the Kansas City Metro
northland. The initial development of the strongest storms is
expected over Central Kansas after daytime heating. West of the
forecast area, initial storms will remain discrete, and with some
directional shear in the first kilometer or two, could see a few
supercells develop out there. However, by the time strongest
convergence along the cold front enters our eastern and northeastern
Kansas Counties, the deep layer shear vector is progged to orient
more parallel to the boundary and with the low-level jet increasing,
is expected to result in upscale growth into some kind of QLCS or
MCS like mode. Depending on the amount of boundary layer mixing that
occurs and how quickly the front propagates, RAP soundings on the
warm side of the boundary have been hinting at inverted-v like
structure below the progged cloud bases, with DCAPE pushing above
1100 J/kg. This type of environment would favor downburst potential
with newer updrafts. But then as upscale growth continues, stronger
cool pool development may lead to strong outflow winds. Current
expectation is that the large hail threat will mainly be confined to
areas well west of Kansas City tied to where a supercell storm mode
is more likely. However, if along the front we have more broken line
segments and still get new updraft development, the steep mid-level
lapse rates and healthy CAPE profiles through the hail-growth zone
may help get hail stones up to around golf ball size. Heading into
the overnight hours, even after FROPA, another area of mid-level
height falls will promote additional lift, and is expected to keep
shower and thunderstorm activity going. While the severe hail and
wind threat may start to diminish, especially as the front moves
toward Central Missouri, continued rainfall may augment hydro and
flooding issues that started earlier this week, especially for areas
north of the Kansas City Metro that were hit hard this week. HREF
proability-matched mean QPF values are roughly around 1 inch, but
there are concerns that these values could be exceeded if this
boundary stalls. Current deterministic CAM guidance suggests that
the stronger storms and showers will be fairly progressive enough to
limit training, with stratiform rain trailing the main system having
fairly low hourly rainfall rates. With most guidance suggesting that
showers will start to weaken as they cross into Missouri, have not
issued a Flood Watch. We will note that some rivers and streams are
running at elevated levels from the heavy rain that occurred earlier
this week, and if rainfall above 1.00 inch falls into those basins,
may send some rivers back to flood stage.

Sunday, the main cold front will pass through by the early evening.
Southern zones in the forecast area may still hit the mid 80s for
temperatures, while northern Missouri and northeast Kansas will be
in the upper 60s and lower 70s for daily highs. Continued H5
disturbances may provide more rain shower activity, but thunderstorm
potential should be limited as there does not appear to a great
opportunity for destabilization. We may see more rain shower
activity reinvigorate early Monday as H5 closed-low sits over the
Upper Midwest, but uncertain how much lift that will provide for the
lower Missouri River Valley. The next work week will feature much
more seasonable afternoon temperatures.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1150 PM CDT Fri Sep 18 2026

VFR conditions are expected across the region for the majority
of the TAF period before TSRA chances increase in the final 6
hours. For much of Saturday, anticipate southwesterly surface
winds before becoming more westerly/northwesterly in the
evening. Thunderstorm chances increase across eastern Kansas and
western Missouri around/after sunset Saturday evening. Decided
to go with PROB30s for all TAF sites given some remaining
timing/placement uncertainty but the PROB30 groups do account
for the most likely TSRA window for this TAF period. With
storms, VIS could drop to MVFR. Behind the cold front, winds to
shift out of the north with CIGs falling to MVFR or lower...this
change looks most likely after 06Z Sunday, but a slightly
earlier progression of the front could lead to shifts in the
closing hours of the TAF period.

&&

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

&&

$$

DISCUSSION...Krull
AVIATION...Macko