-- Discussion containing changed information from previous version are highlighted. --
313
FXUS63 KEAX 040208
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
908 PM CDT Wed Jul 3 2024

.KEY MESSAGES...

- Showers and Storms This Evening and Overnight; Uncertainty with
Severe Potential

- Additional Shower/Storm Development Thursday Afternoon; Conditional
Severe Threat

- Flooding Possible With Heavy Rainfall

&&

.DISCUSSION...
Issued at 402 PM CDT Wed Jul 3 2024

Note, forecast confidence is fairly low. Overnight activity, which
is uncertain because of today`s cloud cover, will largely dictate
Thursday activity.

H3 trough axis is currently moving across the Rockies this afternoon
and has been keeping upper-level flow generally southwesterly. This
is sending a series of H5 short-waves and localized vort maxes into
the upper Midwest and lower Missouri River Valley. Stationary
thermal boundary remains parked from far southeast Kansas across
Central Missouri. Persistent upper-level divergence ahead of the
main trough axis has helped to augment lift and keep sky conditions
overcast for most of the day. The first short-wave perturbations is
approaching the KS-MO state line and has been generating light
shower activity mainly along Interstate 70 and south. Most of the
instability is confined to south of the thermal boundary, with
MLCAPE values around 1500 J/kg. The cloud cover has prevented
further destabilization this afternoon, which is likely the reason
for more general shower activity rather than robust thunderstorm
activity. Earlier this morning, CAMs were showing some deeper cores
attempting to develop, but cycles through the afternoon have held
off on convection. May see a few thunderstorms develop with one of
the passing short-waves, but overall lapse rates are note greatly
impressive. We may again see some wind if we see precipitation
loading, but the boundary layer is not as well mixed as it was last
night. The HRRR along with other CAMs are pointing to stronger
storms developing after 06z this evening along the front that will
begin moving southward as H5 height falls continue overnight. This
will produce more convergence from Interstate 70 and southward. Some
concern that the CAMs may be over estimating the instability a bit.
HREF mean values overnight are generally around 1000 J/kg.
Instability may be better further south toward the Interstate 44
corridor. The low-level jet will increase low-level wind shear
overnight in our southern counties and overall hodographs to
lengthen with the mid-level vort max increasing mid-level flow. If
convection initiates, it may be able to organize. If convection
develops, main issue will be wind gusts around 60 MPH, as LLJ
momentum could be dragged down by precipitation and precipitation
loading could lead to more downburst like storms. However,
confidence in this is rather low. We will also need to watch storm
training trends along the front. Overnight, our southern counties
are expected to see around 0.50 to 0.75 inches of rainfall, which
that itself is not an issue. However, if the probability matched
means from HREF output, between 1.50 and 2.00 inches are realized,
we may see some flash flooding. This has prompted the Flood Watch
for our southern counties. Continued rainfall Thursday may also lead
to more flooding. A lot of this is conditional on realizing deep
convection.

The current front then exits the Ozarks by mid-morning on Thursday.
More short-wave trough action over the Central Plains though will
continue to provide dCVA and result in surface cyclogenesis across
much of Kansas, with surface pressure falls extending eastward into
the lower Missouri River Valley. A trailing cold front will begin to
propagate across Kansas and eventually reach the MO-KS state line by
the middle of Thursday afternoon. The convergence along this front
will be strong, and likely augmented by larger scale synoptic ascent
ahead of the next localized mid-level vort max. Likely will see
thunderstorm development by Thursday afternoon that then continues
into the evening, mainly for Hwy. 36 and southward, though some
activity will make it to the Iowa state line. The main question is
how much instability develops. There will be stronger WAA and theta-
e advection into the area that will continue to keep dewpoints in
the upper 60s to lower 70s across the region. If there are any
breaks in cloud cover or weak subsidence through the morning,
insolation through a moist boundary layer will quickly result in
destabilization. Current HREF has been depicting mean SBCAPE values
near 2000 J/kg. With the surface pressure falls and backing surface
winds, with secondary jet streak moving over, long veering
hodographs will begin to develop. Stronger updrafts will have the
potential to become severe, and could develop supercell structure to
a few of the discrete storms. Mid-level lapse rates are again not
looking that impressive given how moist the column is, but with
rapid boundary layer destabilization and plenty of moisture,
stronger updrafts are still possible. Precipitation loading once
again will present a wind threat with stronger storms. Perhaps
stronger shear could support some larger hail, though with the large
amount of melting not sure hailstones much larger than half-dollar
would survive to the ground. There could be a conditional tornado
threat if the low-level hodographs curve enough at the time of
favorable forcing and lower LCLs, however if areal coverage of
storms quickly increases would expect a lot of disruptions to the
inflow of individual storms. Overall, would be most concerned about
downburst winds with storms tomorrow. Will need a close watch on
meso analysis for trends in both the wind field and instability to
assess threats/hazards with storms. And if there is too much
convective debris from morning activity, we may not see much in the
way of impressive storms. Even if storms are not overly robust, will
still be concerned about lightning activity storms for July 4th
activities, and may still see sub-severe wind gusts. In addition,
PWATs will likely again exceed 2 inches, which could lead to
efficient rainfall production. Again the heavier rainfall may
concentrate south of U.S. Hwy. 50, which could result in more
flooding. Thus, the flood watch will be in effect through midnight
Thursday Night. Overall ensemble probabilities for exceeding one
inch of rainfall in our southern counties is around 30 percent. HREF
probability matched means for 24 hours totals are around 2 inches,
with higher amounts further into the Ozarks Region.

For the remainder of the week into the weekend, temperatures will be
in the upper 80s to lower 90s. Current ensemble probabilities
indicate mostly dry conditions through Friday after the cold frontal
passage. However, more short-wave activity into the weekend will
bring additional rain shower and thunderstorm chances.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
-- Changed Discussion --
Issued at 901 PM CDT Wed Jul 3 2024

Ceilings slowly improving with MVFR conditions returning around
09z for all TAF sites. The shower activity from Kansas has
already moved across the area at all TAF sits and moved east as
of 02z. However the uncertainty with the thunderstorms past 09z
is increasing confidence as the thunderstorm line from Nebraska
looks to be pushing southeast towards Missouri with potential to
be around 06z-09z. This potential for shower and thunderstorm
activity late tonight into the early morning hours with
potential between 09-12z. There is a severe thunderstorm risk
further on Thursday July 4th particularly for areas highlighted
from KMCI, KMKC, and KIXD brining low ceilings, thunderstorms
and winds but it will also depends the activity for overnight
tonight.
-- End Changed Discussion --

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch through late Thursday night for MOZ040-045-046-053-
     054.
KS...Flood Watch through late Thursday night for KSZ060.

&&

$$

DISCUSSION...Krull
AVIATION...Kreller