259
FXUS63 KEAX 120843
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
343 AM CDT Mon Aug 12 2024

.KEY MESSAGES...

- Showers/Storms Through Late Morning Today

- More Showers and Storms Tuesday through Middle of Week

- High Heat Index Values Possible Wednesday Southwest CWA

&&

.DISCUSSION...
Issued at 343 AM CDT Mon Aug 12 2024

Mid-level short-wave axis is close to the IA-MO-NE triple point and
has been forcing a group a showers/storms from NW Missouri into west-
central Iowa during the overnight hours. Warm front currently sits
in far eastern Kansas from just west of the KC Metro toward Fort
Scott KS. The first round of rain that brought a swath of 1.5 to 2.5
inches of rainfall in the western KC metro utilized much of the
instability close to the warm front. As of 08z, MUCAPE in our
counties has dipped to around 500 J/kg. There is still some activity
on-going in south-central Kansas where instability has been higher
as this is deeper into a rich theta-e airmass. For the remainder of
the morning, expecting large scale ascent to maintain showers/storms
primarily north of Interstate 70, and this will push mainly
eastward. At this point, efficient rainfall is still possible with
amounts of 1-2 inches possible, but the lack of favorable
thermodynamics is expected to keep storms sub-severe. HREF mean QPF
north of Interstate 70 is around 1.25 to 1.5 inches. There are a few
pockets where HREF output depicts a 40 percent probability of
exceeding 1.5 inches of rainfall. As for flooding in north-central
Missouri, does not seem favorable at this point. Flash flood
guidance suggest a rainfall rate of 3+ inches in 3 hours is needed
for widespread flooding. For areas closer to Interstate 70 and
southward, there is potential for additional shower activity to fill
in along the warm front as the short-wave continues to dig and large
scale ascent increases. CAM solutions this morning have not been
consistent with development through the remainder of the morning. It
is a situation where the forcing and moisture is there, but the
thermodynamics may struggle to support a convective structure. As
mentioned before, there is some activity in south-central Kansas
that could continue eastward within a wing of stronger insentropic
ascent, but given the lack of any further diabatic heating or other
source of instability, hard to confidently declare robust
development. The greater instability axis dives toward the Ozarks,
so any new development along the leading short-wave may dive south
of the area if it develops. PWATs throughout most of the area are
still around 2.00 inches, and with stronger storms we certainly saw
efficient rainfall production. The good news for the western KC
metro is that most activity should stay north as the warm front
slowly advances toward the northeast. However, should there be more
robust development that finds a way to maintain itself, another inch
of rainfall through Wyandotte and Johnson [KS] Counties could result
in some minor flooding. Once the short-wave passes through, we
should see a break from precipitation for the remainder of Monday
afternoon. Currently expecting temperatures in the western part of
the area to reach the lower 80s as stronger WAA pushes temperatures
upward. Northeast portions of the forecast area likely remain much
cooler with dense cloud cover and precipitation keeping temperatures
in the lower 70s.

Late tonight and into Tuesday morning, another mid-level short-wave
works through the mid-level ridge pattern that will provide
additional kinematic forcing for shower and thunderstorm
development. Another area of dCVA over the Front Range will continue
to provide modest surface pressure falls from the Central Plains
into the lower Missouri River Valley with a thermal boundary likely
somewhere over Central Missouri. Expecting another higher theta-e
airmass at least within the boundary layer to be in place, though
overall instability may still be lower with a saturated column and
weaker lapse rates. Current HREF mean MUCAPE does not exceed 1000
J/kg. Current CAM guidance depicts the bulk of the forcing on the
southwestern third of the CWA, moving through primarily in the mid
to late morning hours of Tuesday. Deep layer shear is coming in
weaker with this short-wave Tuesday compared to the one experienced
early Monday morning. Overall severe threat appears limited. QPF
will also be progged lower given that lack of organization, HREF
mean values generally between 0.25 and 0.75 inches from just west of
KC to Springfield, MO. HREF probability matched mean (PMM) values
for Tuesday morning along this QPF axis is around 1.25 inches. The
strongest forcing and mid-level support exits the forecast area
between 18-20z on Tuesday, but continued isentropic ascent and
higher theta-e airmass may support linger activity. Most ensemble
probabilities maintain at least 20 to 30 percent probability for
some measurable rainfall for the remainder of the afternoon and
evening on Tuesday.

Wednesday, broad warm sector sets up from the eastern Plains into
the mid-Mississippi River Valley, as the ridge axis pushes eastward.
A series of short-waves and vort maxima on the backside will
continue to promote cyclogenesis across the Plains and should see a
steady uptick in surface pressure falls through the afternoon on
Wednesday. Higher theta-e airmass pushes eastward and should start
to see better CAPE, with potential for EML from 700mb-500mb to be in
place that could steepen lapse rates and yield higher CAPE values.
The primary question will be deep layer wind shear through,
especially from eastern Kansas into Missouri. Weaker flow may result
in weaker shear. However, with increasing surface convergence and
pressure falls along an axis of destabilization, could support a few
stronger updrafts. This is largely conditional on early morning
isentropic shower activity clearing in time for this destabilization
to occur. Primary threat would be for storms to produce severe hail
and some damaging wind gusts. Given the high uncertainty of how
Tuesday activity spills into Wednesday morning, will not attempt to
pinpoint mesoscale details at this time. Will also need to keep an
eye on QPF trends heading into Wednesday, as the ground across much
of the area may remain saturated, meaning flooding and other hydro
issues become more problematic. In addition to storm chances, the
push of strong WAA along with higher humidity may have the potential
to yield heat index values in the triple digits, primarily for the
western and southwestern portions of the forecast area. Confidence
at this time is medium-low, as cloud cover and lingering
precipitation drag could greatly keep temperatures much lower.

For the end of the week, additional short-waves may bring more
precipitation chances, with temperatures generally in the upper
80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1224 AM CDT Mon Aug 12 2024

First round of showers is moving eastward, more development is
expected heading into the overnight hours. Ceilings will
gradually drop to IFR by the early morning hours of Monday. Most
precipitation activity should between 12z-14z. There is still
moderate amounts of uncertainty with thunderstorm trends and
timing through the overnight hours.

&&

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

&&

$$

DISCUSSION...Krull
AVIATION...Krull