St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

006
FXUS63 KEAX 200927
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
427 AM CDT Wed May 20 2026

.KEY MESSAGES...

* Cooler conditions continue through the end of the workweek, with
  rainfall chances arriving as soon as Thursday morning (10-30%).
  The greatest chance for rain is overnight Thursday through Friday
  morning (70-80%).

* Low-end chances (20-30%) for rain extend into the weekend with
  temperatures creeping into the upper 70s and lower 80s.

&&

.DISCUSSION...
Issued at 424 AM CDT Wed May 20 2026

A loop of the latest H5 analyses depicts the unwavering nature of
the upper-level trough out west. While this system was enjoying its
West Coast vacation, lee cyclogenesis has begun in northern British
Columbia and Alberta as a 130+ kt jet streak runs over the Northern
Rockies. Over the next 24 hours, this process will produce two
distinct mid-level cyclones. One is expected to hold north along the
U.S./Canada border while the other is pulled south by the upper-
level jet. The latter`s influence may be felt as early as Thursday
as it ejects a series of shortwaves into the region. Guidance
suggests the first shortwave could move through as early as midnight
on Thursday. However, dry air aloft will limit rain potential for at
least several more hours. There are some indications that mid-level
moisture could improve as soon as Thursday morning, but this comes
many hours after the subtle vort max passes by. Rain is not out
of the question during the earlier portions of the day on
Thursday, but it will be reliant on the timing of saturation
aloft relative to that of the shortwave. Given these conditional
circumstances, hourly PoPs have been limited to 10-30% between
06Z and 18Z Thursday. Increasingly southerly mid and low-level
flow throughout the afternoon and evening on Thursday will
bolster rain chances as a second shortwave is introduced to the
region. The coincident timing of the shortwave and moisture
increases confidence in precipitation late Thursday afternoon
through early Friday morning, with the greatest 6-hourly PoPs
(70-80%) occurring overnight and early Friday morning.

As the mid-level low dives south along the Rocky Mountain range, lee
cyclogenesis looks to be induced yet again with a small lee cyclone
appearing just east of the New Mexico border as early as Friday
morning. Although rainfall chances should generally decline
throughout the day on Friday, the primary cyclone is outlooked to
bend northeastward through Nebraska and northwest Iowa late in the
day leading to increased low-level south/southwesterly flow, so WAA
induced showers remain a possibility. Some weak to modest
instability may be able to develop in the southern fringes of the
CWA, but shear looks to remain poor. Regardless, a rogue elevated
and sub-severe storm cannot be ruled out Friday evening.

Increased WAA courtesy of the primary mid-level low will help boost
temperatures into the lower 70s and upper 80s heading into the
weekend. By Saturday morning, the mid-level lee cyclone is expected
to arrive. Ample uncertainty remains on the type of impact this
system could have locally as current projections keep the surface
cyclone and boundary near the southern and eastern fringes of the
CWA. Should the placement be further north, shower and storm chances
would increase with more opportunities for ascent at the ready.
Modest instability also looks to exist south of the surface
boundary, so a further northward progression could open the door for
some degree of convective development Saturday afternoon. Like
Friday evening, though, shear profiles remain unimpressive. A day to
keep an eye on, but nothing to write home about for now.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1048 PM CDT Tue May 19 2026

High pressure continues to settle into the region and has help
improved the MVFR ceilings to VFR across most of the area. Area
of drizzle has pushed into southern Missouri. Winds will
gradually veer from northerly to northeasterly during the
overnight hours. VFR ceilings will scatter out by late morning.

&&

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

&&

$$

DISCUSSION...Macko
AVIATION...Krull