St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

935
FXUS63 KEAX 281115
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
615 AM CDT Mon Sep 28 2026

.KEY MESSAGES...

- Warm and dry conditions expected Monday and Tuesday.

- Several rounds of showers and storms are likely (60-80%
  chance) across the forecast area mid/late week. Heavy
  rainfall is possible, especially Wednesday night into
  Thursday.

&&

.DISCUSSION...
Issued at 326 AM CDT Mon Sep 28 2026

Surface and upper-air observations from 00Z show subtle changes to
the overall synoptic pattern over the last 12-24 hours. Over New
England, the upper trough has caught up to the closed low/Nor`Easter
embedded within the broader upper-level ridge. This system will
gradually be reabsorbed and carried northeast back to the Atlantic
over the coming days. Meanwhile, the upper trough across the western
CONUS is set to continue amplifying. As it does so, the base of the
trough is expected extend flush against the southern U.S. border,
closing itself off from the ~130 kt jet streak protruding into
British Columbia. Between now and Tuesday, conditions look rather
quiet as the axis of the ridge leading the western trough builds
into the region. Some patchy fog may be able to develop across
northern Missouri during the early morning hours on Monday where
winds are light and cloud cover is minimized. Warmer conditions are
expected across the region both Monday and Tuesday, with high
temperatures in the mid/upper 70s along and north of the US-36
corridor. Further south, maximum temperatures are more likely to
settle in the upper 70s and low 80s.

The dry weather will not last long, however, with rain chances
returning as soon as late Tuesday evening. Latest guidance suggests
that the remnants of weakening Hurricane Polo are to lift toward the
southern New Mexico/Texas border on Tuesday, by which point residual
tropical moisture and vorticity would be ingested into the
aforementioned cyclone. This system is then progged to surge
northeastward into portions of the Southern and Central Plains,
introducing heavy rainfall and flooding concerns. Tuesday night into
early Wednesday, showers and thunderstorms are expected to enshroud
much of the Plains as the low level jet intensifies in the vicinity
of the extremely moist airmass. Showers and storms will be most
likely across the northwestern and western portions of the forecast
Tuesday night, gradually expanding in coverage throughout the day on
Wednesday. As things stand now, all portions of the forecast area
have >80% PoPs sometime between Tuesday and Thursday night; for
most, the increased likelihood of rainfall arrives late Wednesday
night into Thursday when PWATs between 1.8 and 2.1 nose into the
area. For context, these values sit roughly around the 99th
percentile compared to both the NAEFS and GEFS climatologies.

While confidence in rain is high, confidence in total rainfall
accumulations is certainly less so. Looking back at LREF
probabilities from the middle of last week up through the most
recent run, there is a clear downward trend in total expected QPF.
However, this alone fails to tell the whole story; instead, high
uncertainty is confirmed by ensemble spreads. For total rainfall
accumulations by Friday evening, there is a 1.5 inch spread between
the 25th and 75th percentiles across the forecast area. For the 10th
and 90th percentiles, spread spikes to about 3.5 inches. Needless to
say, there are substantial challenges in skillfully assigning total
accumulations at this time. This is compounded by unclear frontal
boundary placements which are pivotal in determining key areas to
hone in on for flooding potential. Despite the level of uncertainty
remaining, widespread accumulations of 1.5" to 2" seem to be the
most likely solution at this junction. That said, it will be key to
follow system evolution and model trends over the coming days as
this will guide future updates.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 612 AM CDT Mon Sep 28 2026

Prevailing VFR conditions through the forecast period. As the
morning progresses, expect CIGs to gradually rise and give way
to SCT high clouds later this afternoon and evening with light
easterly winds.

&&

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

&&

$$

DISCUSSION...Macko
AVIATION...Macko