St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

467
FXUS63 KEAX 210856
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
356 AM CDT Thu May 21 2026

.KEY MESSAGES...

* Rain chances return this morning (20-40%). Greater likelihood for
  rain arrives Thursday evening through Friday morning (40-80%).

    - Recent trends have helped qualm (but not eliminate) flooding
      concerns associated with rain chances in the coming days.

* Most river levels continue to recede with a few rivers still
  yet to crest.

&&

.DISCUSSION...
Issued at 355 AM CDT Thu May 21 2026

Upper air analyses now clearly depict a strengthening mid-level low
off of the Northern Rockies. Over the coming hours and days, the
upper-level jet will pull this cyclone to the south as it sends a
couple of pulses through the Central Plains. The first of this pair
is well on its way, having aided in the development of overnight
showers along a mid-level moisture gradient extending from north
central Kansas into southwestern Iowa. As we continue through the
early morning, rain chances will improve ever so slightly across the
region with increased saturation aloft. Morning PoPs have been kept
on the lower end (20-40% along the MO/KS border with lower
probabilities off to the east) given relatively poor forcing.
Southwesterly mid/low level flow is expected to ramp up during the
day, helping guide showers out of northern Oklahoma and southern
Kansas into the area. Thursday evening, a second shortwave ejected
through the Plains will supply a CVA maxima while isentropic ascent
strengthens, especially south. This could set the stage for an
extended period of rainfall beginning late Thursday and lasting
through the early half of Friday. Probabilities for PWATs > 1" over
the course of the event remain both high (near 100%) and widespread,
but a signal for PWATs > 1.5" focuses in on areas south of I-70,
particularly along the southern MO/KS border, early Friday morning.
Trends have been such that QPF has lessened, now narrowing in on
widespread accumulations of 0.25 to 0.5" with locally higher amounts
possible. This has reduced flooding concerns, and in turn, resulted
in changes to the ERO for Thursday and Friday. A marginal risk for
excessive rainfall now exists roughly in the area south of I-670 and
along and west of the I-49 corridors, a downgrade from the slight
risk previously issued. Outside of this narrow area in eastern
Kansas and western Missouri, the CWA is no longer outlooked for
excessive rainfall.

Rain chances over the holiday weekend also appear to be on a
downward trend as a surface cyclone follows more closely to the
southern Missouri border. The greatest opportunity for shower/storm
development (10-30% chance) would occur Saturday afternoon overnight
into Sunday, mainly south of I-70. Contending with weak forcing, a
general lack of instability, and poor shear profiles, anything that
manages to develop would likely be the result of WAA/isentropic
ascent. As such, expectations remain low for weekend precipitation.

The active weather pattern looks to continue into next week with H5
clusters show a deepening mid-level trough west of the Rockies. Not
too dissimilar from this week, several shortwaves are expected to
run across the Plains while the mid-level cyclone is bogged down by
ridging along the East Coast. Though it is a bit too early to
comment on the significance of any rainfall or storms with much
certainty, ensembles do indicate the return of wet weather by
mid/late week. Otherwise, the positioning of the ridge just to the
east will promote southeasterly flow for much of the week, allowing
for temperatures to sit in the mid 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1217 AM CDT Thu May 21 2026

Borderline VFR/MVFR CIGs to persist for the next several hours
before falling bellow MVFR thresholds early/mid morning. Around
sunrise, some very light rain showers are possible, thus
warranting a brief PROB30 at all four terminals on Thursday
morning. Additional light rain may arrive towards the end of the
TAF period, but confidence remains too low to be included in
the TAF at this time.

&&

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

&&

$$

DISCUSSION...Macko
AVIATION...Macko