St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

234
FXUS63 KEAX 181729
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
1229 PM CDT Tue Aug 18 2026

...Updated 18z Aviation...

.KEY MESSAGES...

- Severe thunderstorms are possible today and tonight, with the
  most likely timing from late this evening through the
  overnight hours.

- Near-normal temperatures likely Wednesday into early next week
  with low precipitation chances, mainly early next week.

&&

.DISCUSSION...
Issued at 224 AM CDT Tue Aug 18 2026

A convective system is moving southeast through Nebraska as of 07Z
and how this system evolves through sunrise and beyond will play a
major role in where/ how convection develops/ evolves this afternoon
and through the overnight. Anticipating this system will weaken
as it moves southeast and begins to affect the northwestern
portions of the forecast area early this morning. Instability
is substantially weaker over northwestern and north central
Missouri, which should favor a weakening trend as it approaches
the area. That said, there is some potential for it persist
further southeast and bring some strong wind gusts into
northwestern Missouri early this morning. Cloud cover
associated with the decaying MCS may limit the potential
instability over the norther tier of Missouri and overall, the
slight risk has been consolidated more to the southwestern
extent of the previous outlook. This evening, the surface
pattern will feature an area of low pressure over southern
Kansas, with a what looks like a warm front extending east into
the southern portions of the forecast area. This will lead to
MLCAPE values as high as 2500J/kg across eastern Kansas and
western Missouri. As a subtle shortwave trough moves east,
increasing flow aloft will support deep-layer shear increasing
to over 40 kts. A strong low-level jet will also develop with
strong moisture transport northward into the boundary.
Convergence along this boundary will get the main convective
episode going and will initially support supercells with a large
hail and damaging wind threat, though a tornado or two can`t be
ruled out as well. Over time, this will evolve into a more
linear/bowing segment with damaging winds becoming the main
hazard. Overall, the most likely window for severe storms looks
like roughly 02Z/9PM through 09Z/4AM. In addition to the severe
weather threat, high precipitable water values will support
localized heavy rainfall and potential for flash flooding. The
area is also under a slight risk for excessive rainfall. Looking
over flash flood guidance, values are fairly high 2-3"/hr for
areas where the greatest QPF is situated so will not be issuing
a flood watch with this forecast.

For the remainder of the forecast, temperatures will be closer
to normal for this time of year, which is generally in the
middle to upper 80s. Ensemble mean 500mb heights and anomalies
favor northwesterly flow over the middle of the country with
ridging over the western half of the CONUS and troughing over
the eastern half. This pattern looks generally dry, and that is
generally what the forecast shows. But we`ll need to watch for
embedded shortwaves and/or internal PV anomalies generated from
upstream convection, that may affect the area. These are not
resolvable on this scale, both spatially and temporally, thus
the generally dry forecast.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1225 PM CDT Tue Aug 18 2026

Decaying showers are still present over eastern Kansas and
western MO. We are expecting these to continue to produce
showers at STJ and the KC Metro terminals through at least 19z.
Ceilings are expected to remain VFR through most of this
activity. The cold front moves through later tonight and through
the overnight hours, and is expected to development showers and
thunderstorms across much of the region. The timing for this
seems favorable between 03-04z, then continues into early
Wednesday morning. During heaviest precipitation activity,
periods of IFR conditions are possible. Activity should push out
of the area after 12z Wednesday morning.

&&

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

&&

$$

DISCUSSION...CDB
AVIATION...Krull