St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

620
FXUS63 KEAX 282325
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
625 PM CDT Fri Aug 28 2026

...Updated 00z Aviation...

.KEY MESSAGES...

- Heat will build into the region this weekend and prevail
  through the remainder of the forecast. Heat index values will
  range from near 100 to 105 Sunday through Friday next week,
  with the hottest time frame coming Sunday and Monday when
  highs will approach 100.

- Low chances for precipitation (10-25%), almost nightly/early
  morning, across far northern Missouri and extreme northeastern
  Kansas.

&&

.DISCUSSION...
Issued at 225 PM CDT Fri Aug 28 2026

Water vapor imagery with 500mb heights plotted shows a strong
upper ridge centered over the western Plains. This ridging will
spread to the east this weekend and when combined with
increasing southerly low-level flow, will result in
temperatures climbing into the 90s over the southwestern half of
the forecast area tomorrow, then the entire forecast area
Sunday through the remainder of the forecast. Our current
forecast has highs in the upper 90s Sunday and Monday across
eastern Kansas and western Missouri. But there is some potential
for temperatures to reach or exceed 100 degrees. The model
certainty tool shows roughly a 10-20% chance of this occurring
both Sunday and Monday. For this to be achieved, deeper mixing
would need to occur, resulting in a drier airmass, similar to
the deterministic GFS. This seems to be an outlier and what
appears more likely to occur is a bit shallower mixing and not
quite as dry an airmass. Regardless, the result is heat index
values as high as 105 degrees from Sunday onward. We`ll need to
closely monitor this balance between forecast temperatures and
dewpoints since slightly better moisture, like the deterministic
NAM, would lead to more widespread heat index values closer to
105. Looking at ensemble probabilities for heat index values
reaching 105 or greater, each day next week shows fairly low
probabilities of exceedance, generally less than 10-20%. So
while we may not hit our heat advisory criteria, this will still
be a long stretch of time with unseasonably hot weather with
highs 10-15 degrees above normal and overnight lows,
particularly in urban areas, barely dropping below 80 degrees.
Will continue to make the heat the primary message in our DSS
packet as result.

The other thing to mention with this forecast is the low potential
for precipitation to move into northern Missouri and extreme
northeastern Kansas, on nearly a nightly/early morning basis. PoPs
across the norther portions of the forecast area range generally
from 10% to as high as 25%. For tonight, this is mainly due to
isentropic ascent with a strong low-level jet focusing better
chances further north of the forecast area. Chances diminish Sunday
and Monday night/morning as the ridge axis is moving through. Beyond
this, the ridge shifts east into the Southeast and that allows
shortwaves to influence the area as well as the low-level jet to
potentially focus across northern portions of the forecast
area. This pattern may also support stronger moisture transport
into the area, helping lead to better chances for
precipitation if that can be focused.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 623 PM CDT Fri Aug 28 2026

High pressure is starting to exit the region but will provide
one more evening of mostly clear skies across the area. Winds
will shift more southerly and remain between 5 and 10 kts, which
should also help to hinder fog development early Saturday
morning. Wind gusts pick up during the afternoon on Saturday.

&&

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

&&

$$

DISCUSSION...CDB
AVIATION...Krull