St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

481
FXUS63 KEAX 172335
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
635 PM CDT Thu Sep 17 2026

.KEY MESSAGES...

- Slight chances (15-25%) of storms in NE MO overnight into
  tomorrow morning. More substantial rainfall is expected late
  Friday through Monday.

- A few strong to isolated severe storms are possible Saturday
  afternoon/evening with damaging winds the main threat. Heavy
  rain will also be possible which may lead to localized flash
  flooding across NE KS/NW MO where recent heavy rain fall.

- Hot Conditions persist through Saturday before cooler, more
  seasonable temperatures return early next week.

&&

.DISCUSSION...
Issued at 226 PM CDT Thu Sep 17 2026

Today the local area is under an influence of a upper level ridge
centered over the southern Plains and lower Mississippi River
Valley. This will bring warm temperatures to most of the area south
of a weak surface cold front stretched across northern Missouri.
South of this front temperatures will achieve the low to mid 90s
with heat index values in the 100-105 range. For areas behind the
front across the northern CWA temperatures will hold in the low to
mid 80s. Tonight, the boundary will become stationary near the
Highway 36 corridor as a LLJ gets ramped up and noses into the area.
This will bring the chance for a few storms across the north central
and northeastern Missouri overnight into tomorrow morning. Tomorrow,
the upper level ridge become amplified over the region as the
stationary front lifts north of the area as a warm front. Increased
WAA will aid in highs rising into the upper 80s to upper 90s. Heat
index values will range from the upper 90s to near 105.

We are looking at the potential for an active weekend ahead. There
is increased confidence that the upper-level trough in the Pacific
NW will progress southeast Saturday night, beginning to flatten out
the ridge of high pressure over the SE CONUS. The exit region of the
trough will likely set up over the rockies, favoring the development
of a surface low and synoptic cold front at the surface. There is
still some uncertainty about where this front will set up Friday
night but the current ensemble consensus places the front along NW
MO and extending from the CO foothills into central IA. This
boundary may coincide with the development of a nocturnal LLJ Friday
night. While we are still far enough out that the CAMs can`t resolve
the entire event Friday night into Saturday, there is a signal for
fairly strong CAPE values Friday evening over NW MO. All these
mechanisms favor ascent and we could see the potential for severe
weather, primarily damaging winds, for northern MO Friday night.

Storms will potentially stick around throughout the weekend as
ensemble consensus shows the front stalling out across our CWA as
the trough and ridge fight for dominance over our CWA. This setup
favors the development of shortwaves that could bring several rounds
of showers Saturday and Sunday. A few of the storms on Saturday
afternoon/evening may be strong to severe with isolated damaging
winds the main threat. Deterministic guidance also has PWAT
values near 2.0 inches along the front, which is above average
for this time of year and as a result we could see locally heavy
rainfall along the front. The air behind the cold front looks
to be considerably cooler so we can`t rule out the potential for
convection and storms on Sunday but we will have a better idea
about this potential once we are in range for higher resolution
guidance.

On the bright side, there is high confidence that the cold front
will move through our area Monday with ensemble guidance (25th-75th
percentile) bringing highs down into the 70s for most of the CWA and
low 80s for our southern most counties. Guidance also shows the
upper-level ridge weakening after the frontal passage resulting in
more zonal flow that could keep rain chances around Monday and
Tuesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 634 PM CDT Thu Sep 17 2026

VFR conditions will prevail through the period with few-sct high
clouds forecast. Did introduce MVFR at KSTJ from 12-15z Thurs, but
am not confident in dense fog development due to slightly elevated
surface winds and marginal low-level saturation. Still, KSTJ has a
tendency to overperform when it comes to fog, so will continue to
monitor. Winds become southwesterly between 7-11kts Thursday after
15z.

&&

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

&&

$$

DISCUSSION...73/IPC
AVIATION...Shaw