492
FXUS63 KEAX 211738
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
1238 PM CDT Sat Sep 21 2024

...Updated 18z Aviation...

.KEY MESSAGES...

* Active weather through the weekend

  * Welcome widespread rainfall, especially later tonight
    through Sun

  * Low severe storm and flood threats

* Cooler late weekend into next week - Highs 60s to 70s

&&

.DISCUSSION...
Issued at 352 AM CDT Sat Sep 21 2024

The beginnings of an active weekend were seen early in the overnight
hours as a cluster of storms worked through Kansas and into west-
central and southwest Missouri. A few storms were on the strong to
severe side, primarily winds, in Kansas, before weakening as they
worked into the area and a less supportive storm environment.
Activity does continue early this morning as the parent shortwave
continues to move through southern Missouri, and should remain
largely general thunderstorms to showers. That will be just the
first of multiple rounds of showers and storms through the remainder
of the weekend, including more widespread opportunities to help
relieve recent drought/dryness across much of the area.

Quickly looking big picture, features that will be most responsible
for our activity remain the SW CONUS trough sliding eastward across
the southern Rockies and a northern stream trough working eastward
across the southern Canadian Plains and US-Canadian border area.

For today, shortwave energy coming off the SW CONUS trough will
continue to develop broad surface low over the High Plains and aide
in boosting southerly flow enough to lift the cool front over the
area back northward as a warm front. As this occurs, ongoing
moisture return/theta-e advection will provide broad and persistent
lift and the opportunity for scattered shower and storm activity.
This activity will be markedly further north than last night/this
morning as a result. While there will be some elevated instability
to work with, HREF depictions of 500-1500 J/kg, the effective shear
environment will be such that organization is not expected. Some of
the stronger storms may produce some small hail and gusty winds, but
severe threat is not expected and also reflected within the SPC Day
1 Convective Outlook with Marginal Risk over northwest CWA to
General Thunder elsewhere. Probably of more interest will be the
rain and heavy rain potential. Ongoing and persistent moisture
advection will keep and push PWat values to around 2 inches and
remain through the weekend. With the more scattered nature and lack
of feature to focus/cause training storms, the hydrologic threat
will be low. Rather, the rain is likely to be welcome given the
recent very dry/drought conditions. NBM QPF 24 hour (ending Sunday
1am) probabilities of 1" or greater as high as 50 to 60 percent over
large portions of northern Missouri and 0.5" probabilities largely
70 to 80 percent over the same area. Of note, there are pockets of
40 to near 50 percent probabilities for 2.0". More on that in a
minute.

By late tonight and into/through Sunday, SW CONUS trough will begin
to move out into the Plains, enhancing surface low development and
continued moisture advection and isentropic lift into the area.
Concurrently, cold front sliding southward from the parent Canadian
surface low, enhanced by developing northern High Plains surface
high, will approach and move into/through the CWA. These, plus
better upper level support/lift will work to continue and enhance
shower/storm development and coverage. Bulk of activity Sunday
within the CAW appears to be overriding the cold front, limiting
strong/severe storm development. CAMs suggest frontal boundary will
push far enough south that best strong to severe risk may reside in
the SGF CWA Sunday afternoon. With mean winds roughly parallel to
the front, training showers/storms will provide another opportunity
for areas of moderate to heavy rainfall. NBM 24 hour probabilities
(ending Monday 1am) of 2.0" or greater again peak over northern
Missouri, in the neighborhood of 50 to near 70 percent. This could
provide an opportunity for a flood threat should similar areas see
amounts in excess of 2" to 3" each day this weekend. Even so, threat
remains lower-end given current hydrologic capacity and duration
over which these rains will occur. Lighter precipitation activity
may continue into/through Monday, especially over eastern areas of
the CWA, as the original SW CONUS trough weakens and passes over the
state.

Aside from today, temperatures will be markedly cooler Sunday and
through the work week with highs in the 60s Monday then rebounding a
bit into the 70s rest of the week. Uncertain precipitation
opportunities during the week as well with various depictions of a
closed low developing and parking itself over some portion of the
region.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1235 PM CDT Sat Sep 21 2024

Showers will continue through the remainder of the afternoon and
evening. Cold front moves back through late tonight, and will
result in thunderstorm activity between 04-08z. Timing could be
slightly earlier of the front moves through faster, and then
some uncertainty with how long it will linger. As front moves
through, also expecting a brief period of IFR conditions, with
longer low-end MVFR conditions. Gusty winds expected with the
approach of the thunderstorms.

&&

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

&&

$$

DISCUSSION...Curtis
AVIATION...Krull