St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

308
FXUS63 KEAX 202325
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
625 PM CDT Mon Jul 20 2026

.KEY MESSAGES...

* Hazardous heat continues today with forecast heat indices between
  105-110F. A Heat Advisory is in effect until 9 PM tonight
  areawide, continuing through 7 PM Tuesday for portions of east-
  central Kansas and west-central/central Missouri.

* There is a 30-40% chance of showers and storms in north-
  central and northeast Missouri late tonight and early Tuesday
  morning. The strongest storms could produce damaging wind
  gusts and small hail.

* Cooler temperatures for the remainder of the work week with
  increasing chances for showers and storms mid/late week. Heavy
  rainfall looks to be the main hazard at this time.

&&

.DISCUSSION...
Issued at 219 PM CDT Mon Jul 20 2026

Recent upper-air and surface analyses depict a mid-latitude cyclone
over western Ontario with an attendant cold front draped across the
Northern Plains and another surface boundary just west of the
Mississippi River. Meanwhile, the upper-level ridge that has
engulfed much of the CONUS continues to be suppressed by the cyclone
and various shortwave disturbances running through the mean flow.

Though the upper-level ridge is on a weakening trend, it remains
influential enough for the continuation of hazardous heat this
afternoon. Dewpoints in the mid/upper 70s have held strong with most
sites recording heat indices above 100F (and a few above 105F)
before noon today. Unfortunately, dewpoints are expected to remain
largely unchanged if not slightly higher than current observations
this afternoon given light surface winds and weak mixing. As
temperatures increase this afternoon, expect widespread heat indices
in the 105-110F range. A Heat Advisory is in effect areawide through
9 PM tonight, with a section of counties in east-central Kansas and
west-central/central Missouri staying under a Heat Advisory until 7
PM Tuesday.

As the cyclone advances to the east, it will drag the cold front
observed over the Northern Plains through the Midwest overnight and
through the early morning hours on Tuesday. Storms are anticipated
to develop along and ahead of this front in Wisconsin and Iowa and
perhaps as far west as Nebraska later this evening. CAMs aren`t
particularly excited about the prospect of strong storms closer to
home...many now suggest that storm clusters will decay substantially
before reaching the northern Missouri border, an area where the pre-
existing storms would have to contend with poor shear and limited
upper-level support. Storms may be able to sustain themselves for a
brief period after moving south have held onto 30-40% PoPs across
north-central and northeast Missouri after midnight. The sooner any
storms are able to reach these areas, the greater the chance of
seeing a strong/severe storm. The primary hazard would be damaging
winds, but trends point to weakening storms by the time they reach
northern Missouri. Additional storm development along the cold
front as it moves through Kansas and Missouri is not expected
given a stout layer of dry air in the low/mid levels. For most,
the only impact from this frontal passage will be cooler
temperatures...though areas under the Heat Advisory through 7 PM
Tuesday (generally south of I-70) may not get as much reprieve
from the heat until Wednesday. Temperatures will continue to
gradually cool as we progress through the remainder of the work
week. but a rebuilding ridge looks to heat the region back up
over the weekend.

Rain chances will return midweek as a series of shortwave
disturbances roll through the Plains, interacting with the remnants
of Tropical Depression 2 and resulting in a setup almost
reminiscent of a Predecessor Rainfall Event (PRE). During
midweek, high pressure is expected to build across the Southern
Plains as TD 2 drifts into the western Gulf. The proximity of
these features will allow deep tropical moisture to wrap
anticyclonically into the Southwest, Great Plains, and Midwest.
Our first chance at precipitation will arrive Thursday morning,
likely in the form of a decaying complex of showers/storms out
of western/central Kansas...currently, 40-50% PoPs exist in the
western portions of the CWA for this reason. Greater chances
(60%+) arrive overnight Thursday into Friday morning when the
low-level jet intensifies, pulling more tropical moisture into
the area. Forecast PWATs currently sit in the 2-2.5" range which
is well above the 90th percentile climatology for TOP.
Unsurprisingly, WPC has highlighted much of the area in a Slight
Risk for excessive rainfall on both Thursday and Friday. Though
we are still a bit of a ways out, it does appear we are looking
at some degree of a heavy rain setup for the latter half of the
week.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 625 PM CDT Mon Jul 20 2026

VFR conditions prevailing at all terminals through the forecast
period. Some diurnal cu lingers at downtown terminals, but no
flight impacts are expected. Primary forecast impacts will be
from a passing cold front from the northwest, which will impact
terminals between 8-11z. Winds expected to swing from the
southwest towards the north with the passage of the front. There
is some indication from guidance that isolated showers/storms
are possible with the passage of the cold front, but confidence
in this solution is low, so have left out mentions of this in
current TAF issuance. Otherwise, no other flight impacts are
anticipated through the remainder of the forecast period.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 9 PM CDT this evening for MOZ001>008-
     011>017-020>025-028>033-037>039.
     Heat Advisory until 7 PM CDT Tuesday for MOZ040-043>046-053-
     054.
KS...Heat Advisory until 9 PM CDT this evening for KSZ025-102>105.
     Heat Advisory until 7 PM CDT Tuesday for KSZ057-060.

&&

$$

DISCUSSION...Macko
AVIATION...SPG