St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

708
FXUS63 KEAX 131124
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
624 AM CDT Sun Sep 13 2026

.KEY MESSAGES...

- Multiple rounds of showers and storms are expected this week, especially
  Monday night through Wednesday across northern Missouri and
  northeastern Kansas. The threat for flooding is increasing,
  especially north of the Missouri River.

- Well above normal temperatures are likely Monday and Tuesday
  along and south of the I-70 corridor. Heat index values may
  climb into the 100 to 105 range.

&&

.DISCUSSION...
Issued at 238 AM CDT Sun Sep 13 2026

It`s another complex and challenging forecast tonight as quasi-zonal
flow continues across the middle of the country, with stronger jet
energy to our north and low-level jet fed storms across eastern
Kansas this morning. Through the remainder of the overnight into
Sunday morning, low-level flow will increase further north across
northeastern Kansas and northwestern Missouri. This is resulting in
renewed convective development from north central Kansas into
northeastern Kansas. As this low-level jet, and convergence on its
nose, shift east this morning, we should see showers and storms
drift east as well, moving into northwestern Missouri as result.
With the waning of the low-level jet during the day, precipitation
should decrease with time. Tonight however, as the low-level jet
reinvigorates, strong moisture transport will lead to anomalously
high precipitable water values streaming into eastern Kansas and
western Missouri. We should see new convective development anywhere
from eastern Kansas to western Missouri, most likely in the 06Z to
09Z time frame, on the nose of the low-level jet. This corresponds
to very strong isentropic ascent from the 305K surface through the
310K surface. Given all these trends, have decreased PoPs through
the day, then ramp them up again tonight into tomorrow morning. While
the overall threat of severe weather looks low today and tonight,
can`t rule out a strong storm capable of some strong winds and
hail, especially tonight into tomorrow morning.

Additional rounds of showers and storms are likely through at least
the middle part of the week. The setup for Tuesday night into
Wednesday morning looks particularly interesting with regards to
heavy rainfall. A frontal boundary is likely to stall in the area
with deep flow generally parallel to that boundary. Copious amounts
of moisture are transported north into the area from a strong low-
level jet. This leads to precipitable water values above the 99th
percentile, pushing 2 to 2.25". With deep flow parallel to the
boundary, training storms are likely, and with the anomalously moist
airmass in place, heavy rainfall and potential for flash flooding is
becoming more likely. A large slight risk for excessive rainfall has
been placed over much of the forecast area. It`s possible, as
confidence in placement and magnitude increase, this will be
upgraded. We may need a flood watch at some point in the next
day or so to account for the increasing risk of flooding
rainfall. Cumulatively, the forecast continues to show
widespread 3-5" rain amounts for northern Missouri, mainly north
of the Missouri River.

With regards to the potential for heat, the southern portions of the
forecast may see highs in the low to mid 90s Monday and Tuesday,
with dewpoints climbing into the low to mid 70s. This leads to heat
index values in the 100 to 105 range. It`s possible a heat advisory
will be needed for a portion of the forecast area Monday and
Tuesday. But given the potential for storms and cloud cover,
confidence is still somewhat low at this point.

&&


.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 621 AM CDT Sun Sep 13 2026

VFR conditions are likely through the forecast. Light easterly
to southeasterly winds are expected through the period with a
chance for thunderstorms late tonight/early tomorrow morning.
Have added a PROB30 mention for this potential.

&&

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

&&

$$

DISCUSSION...CDB
AVIATION...CDB