St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

729
FXUS63 KEAX 090249
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
949 PM CDT Tue Sep 8 2026

.KEY MESSAGES...

- Hot conditions may continue into Wednesday for areas in
  central and southern Missouri.

- A few strong to severe storms are possible late this evening
  into the overnight hours, mainly across northern Missouri. And
  again Wednesday afternoon to evening, mainly along and south
  of I-70.

- Cooler/more seasonal temperatures move into the area for the
  latter half of the week and through the weekend.

&&

.UPDATE...
Issued at 945 PM CDT Tue Sep 8 2026

Allowed the extreme heat warning and heat advisory to expire
earlier this evening. It is possible hot temperatures will
linger in far southern and southeastern portions of our forecast
area on Wednesday. However, confidence is too low at this time
for issuance of an additional heat advisory, given the approach
of a cold front from the north during the day and potential for
showers and storms in proximity to it. We will take a closer
look at this potential during the overnight hours.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 205 PM CDT Tue Sep 8 2026

Broad 500-hPa ridging remains centered over the central CONUS. A
shortwave and associated low pressure system are working across
southern Canada with a cold front draped across the Upper
Mississippi River Valley and into the Northern Plains. While
today remains hot, this cold front will continue progressing
south across MO tomorrow, which will bring some much needed
relief from the heat and multiple rounds of showers and storms.

Broad subsidence and dry air through the column have resulted
in clear skies across northern MO and northeastern KS today.
This will allow temperatures to rise into the upper 90s to near
100 degrees once again today with heat indices climbing above
105 degrees this afternoon. An Extreme Heat Warning remains in
effect for the KC Metro and areas south and west through 8 PM
this evening. A Heat Advisory is in effect for areas along and
southwest of a line from Bethany to Columbia through 8 PM. This
should be the last day of heat related headlines. As the front
moves through tomorrow, cloud cover and precipitation chances
should mitigate the potential of reaching advisory criteria.
Areas across the far southern portion of the CWA (Linn (KS),
Bates, and Henry counties) may reach heat indices of 105
degrees, but these conditions shouldn`t last for more than 1-2
hours, so have opted to hold off on extending the heat products
for these areas.

As previously mentioned, a cold front is moving south-southeast
across NE and IA this afternoon and will continue to progress
into northern MO overnight tonight. 1500-2500 J/kg of MUCAPE is
expected to pool along the frontal boundary, which paired with
the lift associated with the front will create a setup for
storms as the front moves through. The best timing for storms
across northern MO appears to be as early 3 AM and lasts through
sunrise before chances begin to diminish. Shear values are
marginal with 20-30 kts of deep layer shear, which is enough to
get some organization of storms, Model soundings across northern
MO feature dry air in the low- levels creating inverted-V
profiles. While most of the instability is elevated on the
front, these profiles favor pulsey downburst storms, which may
have enough downward momentum to punch through the stable
surface layer and bring strong to damaging winds to the surface.
This thinking aligns with the SPC Day 1 Convective Outlook,
which outlines northwestern MO in a Marginal (Level 1 of 5) Risk
for severe weather with the main hazard being damaging wind.

As the front continues to work south through the morning,
showers and weak storms will be possible (50-70%), but severe
weather is not anticipated as the low-levels become more
saturated and the inverted-V sounding profiles becomes less
prominent. MUCAPE values rebound through the afternoon and
evening as the front approaches the southern periphery of the
CWA bringing a renewed severe risk. As temperatures warm and
daytime mixing occurs, the inverted-V profile returns beneath
2000-3000 J/kg of MUCAPE. This once again makes strong to
damaging winds the primary threat, although marginally severe
hail cannot be ruled out. This severe threat largely exists from
the KC Metro southward during the late afternoon and early
evening and into the overnight as the front exits the southern
portion of the area.

Current expectations are for 0.5-1" of precipitation across the
area, with locally higher amounts possible. Given the dry
stretch of weather that the area has been locked in, it will
take 1.5-2" of rain in 1 hour and 2.5-4" in 3 hours to create
flash flooding concerns. Locally heavy rainfall will be
possible with the strongest storms given the 2-2.5" PWATs that
are currently in place across the area. Thus, localized flash
flooding is possible, but pinning down an exact threat area is
dependent on how individual storms evolve.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 103 PM CDT Tue Sep 8 2026

We will dry out briefly on Thursday and Friday with highs in
the mid to upper 80s. However, we are shaping up to have a wet
weekend. A surface low will lift out of Minnesota into Ontario,
dragging an associated cold front through the Northern and
Central Plains into our area. This front will bring widespread
rain and highs will remain in the mid 80s for most of the
forecast area. Currently models are holding rain off until late
Friday night/early Saturday morning.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 704 PM CDT Tue Sep 8 2026

Main concern for the next 24 hours is the cold-frontal passage
on Wednesday and associated shower/storm chances and wind
shifts. VFR expected tonight with south to southwest winds
around 10 kt. There may be some LLWS late tonight as a low-level
jet nocturnally intensifies; however, winds may stay just
elevated enough at the surface to meet TAF thresholds. On
Wednesday, increasing chances for showers in the morning and
storms in the afternoon (50-70 percent chance), but pinpointing
more precise timing remains low confidence at this time. As a
result, have kept PROB30 mention for SHRA/TSRA from late morning
through the afternoon at the TAF sites for now. Winds will shift
sharply to the northwest after frontal passage, which looks to
be 15-18z at STJ and 17-20z at the KC TAF sites.

&&

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

&&

$$

SHORT TERM...Carothers
LONG TERM...IPC
AVIATION...CMS
UPDATE...CMS