St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

895
FXUS63 KEAX 181128
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
628 AM CDT Thu Jun 18 2026

.KEY MESSAGES...

- Quiet, cooler weather to close out an active week.

- Next opportunity for active weather overnight Saturday through
Sunday, with increasing concerns for severe/hydro impacts.

- Around seasonally normal temperatures through the forecast period.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 259 AM CDT Thu Jun 18 2026

In the wake of the cold front that pushed through late yesterday,
conditions across the area will remain cooler and drier through the
day today. There is some chance (15-30%) for light rain showers
across the area, with adequate mid-level moisture invigorated by a
shortwave impulse. However, with relatively dry low-levels post-
frontal passage, not overly confident that rain showers will be
vigorous enough to have much of an impact at the surface. Have
included mentions of sprinkles in the forecast with this thought in
mind, as well as light rain showers to account for anything that`s
able to reach through the drier low layers of the atmosphere.
Persistent CAA and northerly flow, coupled with cloud cover through
most of the day areawide, will contribute to lower highs tomorrow in
the mid-upper 70s. As clouds clear out from the north later in the
day, there`s the potential for temperatures to rise some as surface
heating takes effect in those areas. However, generally low
confidence (10-15%) in breaking the 80s tomorrow. Friday looks much
the same, with a small disturbance increasing PoPs (30-50%)
generally south of I-70 through Saturday.

Going into Saturday, the focal point of any severe concerns has
effectively shifted westward with subsequent forecasts. As high
pressure slides off towards the east, a shortwave trough will eject
off the Rockies. As this disturbance traverses eastward through the
day, a surge of instability out ahead of the disturbance will prompt
thunderstorm development that gradually evolves upscale into an MCS,
which is expected to impact our forecast area overnight into Sunday.
Conditions remain relatively favorable for continued storm
sustenance as it moves into eastern KS/western MO, with strong
effective bulk shear along the surging LLJ and ample MLCAPE despite
marginal SBCAPE, alongside sufficient mid-level lapse rates. As
storms progress further eastward through the night, primary concerns
would be damaging winds across our area, with an isolated
tornado along the leading edge possible from enhanced low-level
SRH through the LLJ. The primary concern for Saturday
night/Sunday morning, though, is excessive rainfall/flash
flooding. As the MCS progresses eastward and continued storm
development on the surging front is favored, the complex will
tap into an environment characterized by anomalously high PWATs
at/around 2" with surging south/southwesterly flow out ahead of
it, indicating very efficient rainfall. Deterministic guidance
has already started painting 2-3" of rainfall across the area as
the complex pushes through, with probabilistic guidance
indicating as high as a 10-25% chance of exceeding 2 inches over
6 hours in northwestern MO/northeastern KS. This approaches
current 6-hourly flash flood guidance across those northwestern
tiers of counties. Coupled with antecedent dry conditions across
this area over the previous few days, this could lead to more
water resistant soil, which could exacerbate flashiness under
excessive rainfall. On the opposite end of the spectrum,
excessive rainfall in areas that may see rainfall on Friday will
have to contend with saturated soils creating enhanced runoff
with more robust rainfall, which will also contribute to
enhanced flashiness. With these factors in mind, future
forecasts will need to continue to monitor the trend to evaluate
its severity and persistence, especially as more CAM forecasts
enter that time period.

The complex will push across our forecast area through the day
Sunday, gradually shifting concerns of excessive rainfall towards
the east through the day before clearing out of our area by Sunday
night. Temperatures are expected to climb back into the 80s by
Saturday, before cooling back down to the 70s Sunday into
Monday.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 259 AM CDT Thu Jun 18 2026

As the shortwave trough and associated storm complex moves off
towards the east, PoPs will clear behind amplified ridging Monday
through Tuesday. By Wednesday, an upper-level trough will dig down
from the Central Plains, with an associated cold frontal boundary
draping across the area and increasing PoPs through the end of the
forecast period. At the synoptic scale, there is some variation in
forecast solutions over our area by deterministic guidance. This
isn`t atypical to see in the extended forecast, especially under the
zonal/northwest flow regime we appear to find ourselves under with
ridging over the southwest CONUS and general troughing out to the
north and east. Future forecast iterations will need to see greater
consistency in solutions realized before any definitive statements
can be made about weather in the extended period. Otherwise, high
temperatures are expected to generally remain around the 80s, with
pleasant overnight lows in the high 50s/low 60s.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 625 AM CDT Thu Jun 18 2026

Currently VFR at all terminals. Watching some elevated rain
showers off in northern Missouri, not confident that these will
produce prevailing light rain at terminals due to dry low-
levels, so have elected for a PROB30 mention during the early
morning into the afternoon. If light showers do occur at
terminals, not expected any impacts to visibility or ceilings.
Otherwise, expecting cloud ceilings to clear out around 20-22z,
with generally northwesterly winds becoming variable around
3-4z tonight.


&&

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

&&

$$

SHORT TERM...SPG
LONG TERM...SPG
AVIATION...SPG