St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

142
FXUS63 KEAX 132303
AFDEAX

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

.KEY MESSAGES...

- Heavy rainfall leading to flooding is the primary concern with
  multiple rounds of showers and storms expected this week.
  Flood risk appears to be greatest north of the Missouri River.

- Slight Risk (Level 2 of 5) for severe weather for extreme
  northwestern portions of Missouri on Monday evening. There is
  a brief window where all hazards may be possible, but this is
  low probability. Showers/storms to increase in coverage over
  time with a diminishing severe risk overnight.

- Marginal Risk (Level 1 of 5) for severe weather for much of
  the forecast area on Tuesday. Damaging wind gusts are the main
  concern.

&&

.DISCUSSION...
Issued at 251 PM CDT Sun Sep 13 2026

Weak, quasi-zonal flow continues today with the surface boundary
having slid to the south of the forecast area. Overnight showers and
storms had mostly waned by sunrise, though some renewed development
was observed in eastern Kansas earlier this morning. A cursory
mesoanalysis investigation yielded the discovery of small area
of low- level frontogenesis that helped promote this resurgence
on the edge of a weakening low-level jet. Showers and storms
continued to work their way into our southeastern Kansas
counties this afternoon. With cloud tops warming substantially
over the course of the day, only a couple of light showers
remain with most remaining dry.

As we proceed into the late evening and overnight period, our rain
chances will increase once again as the low-level jet ramps up over
the Plains and kicks off elevated showers and storms. PWATs are
forecast to rise to around 1.8" with the moisture surge. With
elevated instability and shear, there may be a brief period
overnight where we could see some small hail and gustier winds, but
even these more organized storms should remain sub-severe. The main
concern would be heavy rainfall, particularly within a corridor
south of US-36 and between I-35 and US-65. It is just to the
northwest of this corridor where development is expected to occur on
the nose of the intensifying low-level jet roughly around midnight.
Northwesterly steering flow will guide storms to the southeast along
a strong 310K isentropic gradient as the night progresses, further
fueling efficient warm rain processes. WPC has highlighted the
northwestern and western portions of the forecast area in a Slight
Risk (Level 2 of 4) of excessive rainfall for reasons such as these.

Warmer conditions are expected on Monday as a warm front approaches
from the southwest. The question of how warm it will be depends
heavily on the speed of the boundary with cloud cover clearing in
its wake. Currently, maximum temperatures in our far south are
forecast to top out in the mid 90s, but this is assuming we clear
out rapidly after sunrise. Dewpoints in the low/mid 70s will keep
heat index values mostly in the upper 90s but some locations that
are able to heat up quickly may be able to approach 105. The warm
front is not expected to make it through northeast Missouri by
sunset, so temperatures may only top out in the low/mid 80s in those
areas.

Behind the warm front and ahead of an approaching cold front,
isolated storms may be possible across northwestern Missouri late
Monday afternoon and evening. By this time, moderate instability
will have built in across the region with around 35-40 kts of deep-
layer shear. There is a non-zero chance of some sort of discrete
development in the warm sector, but this potential seems to be
highest further north in eastern Nebraska and southern Iowa.
Currently, it seems the more likely scenario for far northwest
Missouri is that it gets clipped by upscale growth along the cold
front later Monday night. SPC has highlighted a sliver of northwest
Missouri in a Slight Risk (Level 2 of 5) for severe weather tomorrow
night for which all hazards could be possible. The severe threat
would likely peak between 6 PM and 9 PM before gradually lessening
through the overnight period.

The cold front will continue moving to the southeast over the course
of the day on Tuesday, bringing widespread rain and storm chances to
the region (best chances remain north of I-70 but still have 40-50%
PoPs further south). Much of the forecast area is encompassed in an
SPC Marginal Risk (Level 1 of 5) that day, but the greatest threat
remains the heavy rainfall with PWATs in excess of 2.0" and very
strong isentropic ascent parallel to the boundary and on the nose of
the low-level jet. Except for a few of our southeast counties, WPC
has enshrouded the area in another Slight Risk (Level 2 of 4) of
excessive rainfall on Tuesday. By Wednesday morning, the cold front
will have effectively stalled out along our southern CWA border,
only to ever so slightly drift back northward over the course of the
day. Though the setup is not quite as concerning from a rainfall
production standpoint, any additional rain on top of what had fallen
on Tuesday could exacerbate any existing flooding and flash flooding
concerns. That is, by Wednesday, it doesn`t appear that it will take
much cause flooding problems, and for this, WPC has included areas
generally north of I-70 in yet another Slight Risk (Level 2 of 4)
for excessive rainfall. Additional rainfall is possible Thursday and
beyond but these forecasts are lower confidence at this stage.
Regardless, between now and Friday night, we could see a large swath
of 3"+ total rain accumulations across northwestern Missouri and
northeastern Kansas, with isolated spots potentially exceeding 5".
Along and south of I-70, the cumulative rainfall accumulation
forecast is lower, ranging from 0.5" in our far southern tier
of counties up to around 2-2.5" in the vicinity of I-70. It is
very likely that a Flood Watch will be necessary for at least
part of the forecast area by this time tomorrow.

&&


.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 559 PM CDT Sun Sep 13 2026

VFR conditions are expected to prevail throughout the forecast
period. Scattered showers and thunderstorms are possible north
of I-70 after 06Z tonight. These storms may lead to some brief
visibility restrictions, but should be high based enough that
impacts will be minimal. Easterly winds are expected through the
overnight, but winds will turn clockwise after sunrise and
increase in intensity becoming southerly and gusty Monday
afternoon.

&&

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

&&

$$

DISCUSSION...Macko
AVIATION...BT