St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

364
FXUS63 KEAX 271128
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
628 AM CDT Sun Sep 27 2026

.KEY MESSAGES...

- Isolated to scattered showers again today, mainly for areas south/east
  of I-35. A few thunderstorms are possible as well, but severe
  weather is not expected.

- The potential for heavy rain and flooding for the middle of
  the week is increasing. Multiple rounds of heavy rain are
  expected in the region from Tuesday night through Thursday.

&&

.DISCUSSION...
Issued at 221 AM CDT Sun Sep 27 2026

Water vapor imagery shows a shortwave trough over northern Missouri,
slowly moving eastward. It`s progress is being hampered by the the
deep upper low/ Nor`Easter over the eastern US that is stuck within
a broad upper ridge. This is close to a Rex block setup but not
quite there just yet and it seems unlikely to evolve into a true
blocking pattern. Regardless, it is still slowing the progression of
waves through the middle of the country. There is another wave,
potentially a subtle internal PV anomaly, leading to showers and
storms in southeastern Kansas as of 07Z. with the near blocking
pattern to the east, this wave will meander over/through the
southern half of the forecast area today, leading to continued
isolated to scattered showers and thunderstorms, mainly south/ east
of I-35. While we`ll see greater instability, especially across
eastern Kansas and far western Missouri, shear remains weak so
severe weather is not anticipated. Precipitation chances should
finally start to wind down by 03Z to 06Z Monday, leading to dry
conditions for Monday into Tuesday.

Focus then turns to the potential for widespread heavy rainfall and
flooding for the middle to later portions of the work week,
Tuesday night through mainly Thursday. From a synoptic
perspective, this pattern flashes heavy rainfall. In the upper-
levels, a potent shortwave trough will be moving into the
Southwest. This will help draw copious amounts of mid and upper-
level moisture from the Pacific into the central US. This
moisture is will be the remnants of what is currently Hurricane
Polo. In the lower-levels, a broad high pressure area over the
eastern US will lead to a strong moisture transport from the
Gulf northward into eastern Kansas and western Missouri. This
combination of rich lower-to-mid-level moisture and upper-level
moisture will lead to very anomalous precipitable water values.
In fact, these values are 3+ standard deviations above normal
for this time of year, above the 99.5 percentile for a large
portion of the area, and at the max values on the NAEFS
percentiles and GEFS M-climate. Ensemble guidance shows roughly
a 10-20% chance for at least four inches of rain for the run
ending at 7PM Friday. This jumps to 20-30%+ for total rain of at
least 3 inches through the same time frame. With all that said,
there remains a fair amount of uncertainty on where the
heaviest rains will actually setup. That will largely depend on
where the strongest forcing sets up as the shortwave ejects into
the Plains Wednesday into Thursday as the system takes on
distinctive mid-lattitude cyclone characteristics, with a
notable deformation area, a warm frontal region extending
eastward, and cold front extending southward. Each of these
areas will provide a focus for heavy rainfall and placement of
these features will be key to defining the areas with the
greatest flooding potential.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 628 AM CDT Sun Sep 27 2026

VFR conditions currently may trend to MVFR (20-40% chance) with
ceilings around 1500 ft. There is some potential (15-20%) for
IFR ceilings as well from later this morning through the
afternoon. These conditions are more likely across northeastern
KS into northwestern MO and adjacent areas of NE and IA, with
lower probabilities further south and east. While confidence
isn`t particularly high on these conditions occurring, with
chances less than 50% for the terminals, have maintained the
mention in the forecast. Based on HREF probabilities, conditions
likely trend to VFR by 06Z to 09Z tomorrow morning. Winds will
be light through the forecast with winds generally from the east
to southeast.

&&

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

&&

$$

DISCUSSION...CDB
AVIATION...CDB