603
FXUS63 KEAX 221133
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
633 AM CDT Sat Jun 22 2024

.KEY MESSAGES...

- Isolated/Scattered Storms Tonight; A Few Severe Possible

- Hot and Humid Over Next 7 Days

- Additional Shower/Storm Chances Through Midweek

&&

.DISCUSSION...
Issued at 346 AM CDT Sat Jun 22 2024

H5 short-wave perturbation over Iowa will continue to moving toward
the Great Lakes Region as a another short-wave/vort max over the
Rockies develops and is set to eject across the Central Plains later
this afternoon. This will continue to deamplify the H5 ridge pattern
that has aided in bringing warm and humid conditions to the region
this weekend. The dCVA with this short-wave over the Front Range has
been intensifying resulting in surface cyclogenesis across the High
Plains during the early morning hours. Already starting to see
modest pressure falls into the eastern Plains and western portions
of the lower Missouri River Valley, and with this surface flow has
been slowly backing. This has continued to provide enhanced theta-e
advection heading into the overnight hours. Moisture transport
between 850-700mb has been stronger than originally anticipated
which has largely eliminated the EML that had been present the past
few days, and current GOES-16 satellite products show cloud cover
over much of Central Kansas this morning that will shift eastward
with the cyclone tracking across the area. There is some low-end
potential to see a few pop-up showers through the afternoon with
warm and moist boundary layer in-place, though if we see increasing
cloud cover prior to noon, destabilization will not be as rapid as
it was on Friday afternoon. Kinematic forcing starts to increase
after 21z this afternoon when the rate of H5 height falls increases
along with surface pressure falls and convergence along the trailing
cold front. The cold front will be the main feature of focus for
eventual convection initiation across our forecast area. CAMs
solutions have been wavering since last night with respect to
favored timing of CI. With the HRRR specifically, some runs has
started CI as early as 21z, with other holding off until 00z when
the front has reached about the Interstate 35 corridor in Central
Missouri. While the convergence and other kinematic support may be
present as early as 21z, there is concern that HRRR/RAP may be
mixing out too rapidly and not handling the cloud cover incoming
from central Kansas overly well. While temperatures in the upper 90s
may be possible, the mixing of dewpoints down into the lower 60s as
indicated by the HRRR may be too strong. Thinking it will take a bit
longer for boundary layer destabilization and will need the cold
front to be much closer for sufficient convergence. Therefore,
thinking most favorable timing for CI will be after 23z this
evening, and perhaps may hold until after 00z. One factor benefiting
CI is the cap is much weaker with the lack of EML. However, while CI
may be easier to come by with this moisture advection, it is
impacting the mid-level lapse rates considerably which may play a
role in updraft strength once CI occurs, and also will limit
coverage of storms. Overall MLCAPE and SBCAPE values will be easy to
realize with the high theta-e boundary this afternoon, HREF mean
values in the ballpark of 2000-2500 J/kg. With cold front and
surface cyclone creating enough convergence, CI should be able to
get going. The main question is how strong can the activity get, and
will it be maintained and how that changes areal coverage. Mid-level
lapse rates may struggle to steepen beyond 7.0 C/km today, and will
be battling at 700mb temperature near 12.0C. Updrafts close to the
front with 0-6km bulk shear values between 30-40 kts may quickly
become sheared apart if the updrafts are not overly wide. Perhaps
stronger low-level storm-relative inflow could help feed a stronger
moisture content into the storms to overcome this, but ideally would
need better mid-level buoyancy for parcel ascent to continue. With
that being said, initial discrete storms along the front will
primarily pose a wind threat, especially if a well mixed boundary
layer fosters high theta-e deficits by late this evening that could
generate stronger evaporative cooling. Although there is some CAPE
present within the hail growth zone, the potential for stronger
storm-relative inflow with weaker mid-level lapse rates likely
limited the large hail threat though still could see quarter to half-
dollar size hail with stronger updrafts. With backing surface winds
ahead of the approaching cyclone, low-level hodographs will
demonstrate clockwise curvature that could yield 0-1km SRH values
near 150 m^2/s^2 in close proximity to the cold front. This may be
able to support a brief tornado if updrafts are able to overcome the
weaker low-level lapse rates and become a supercell. However,
depending on initial storm motions though and increasing deep layer
shear, the discrete storm updrafts may become too quickly disrupted
before surface vorticity can be effectively realized in our area.
Better environment for a tornado threat will be further north and
northeast of our counties. Therefore, tornado threat appears very
limited at this time in north-central Missouri, and will mainly
focus on damaging wind threat with storms. Eventually, the low-level
jet ramps up and isolated/scattered storms will start to congeal
into a few clusters. If the boundary layer remains well mixed, some
of the LLJ momentum may be transported downward that would continue
a damaging wind threat with storm clusters heading into the evening.
Again though, some storms may end up being very short-lived if the
kinematics and moist boundary layer can`t overcome the meager mid-
level lapse rates. Storms should then exit the area by early morning
Sunday as the cold front moves through the area. With respect to
QPF,  the front looks to be rather progressive across our area which
should limit most hydro related concerns. The GEFS and other
ensemble suites have rather high probabilities for QPF of at least
0.10 inches, generally above 60 percent for areas along and north
Interstate 70 in our forecast area. The GEFS does have a swath of 30-
40 percent probabilities for at least 0.50 inches of QPF as the low-
level jet ramps up across portions of Central Missouri. The HREF
mean has not been overly excited with QPF, generally between 0.25-
0.35 inches for most areas. Local probability matched mean values
for QPF from the 00z HREF has a few pockets of 1.5 inches, which
could be realized with more robust updrafts in a environment with
PWATs approaching 2". Expecting anywhere between 0.25 to 0.50 inches
for areas that seems thunderstorms this evening, with localized
amounts between 0.75 to 1.00 inch possible. Will need to monitor a
few rivers in streams in north-central and northwest Missouri should
heavier rainfall activity occur.

After the front passage on Sunday morning, most deterministic model
guidance depicts the mid and upper-level ridge amplifying again that
will bring another H5 height regime across most of the region and
promote southerly flow at the lower-levels of the troposphere. The WPC
Cluster Analysis for Monday through Thursday has most members in
good agreement for prominent ridging that will bring warm
temperatures and humid conditions for most of this week. Amongst NBM
members, the inner-quartile values are between 97 and 101F for most
points in our forecast area, with a consistent signal for dewpoints
in the upper 60s to lower 70s. This is expected to yield triple
digit heat index values multiple times next week, and may see a few
days where this meets or exceed 105. In addition, a few vort maxes
may drive around the ridge axis that could bring periods of
precipitation. Right now the best signal for accumulating rainfall
and storm chances is on Tuesday with a short-wave that drops out of
Canada, and most ensemble suites also focus increasing probabilities
for rainfall through the middle of the next work week. With
temperatures in the mid to upper 90s and dewpoints in the 70s, could
potentially see a boundary layer that promotes potential for
stronger storms and perhaps may see some severe potential, though
this will largely depend on how strong mid-level flow is and the
resultant deep layer shear environment. Will also need to keep a
closer eye on QPF trends and implications for river flows from
eastern Kansas to central Missouri.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 631 AM CDT Sat Jun 22 2024


VFR conditions oversee the 06Z TAF period. The scattered, upper-
level cloud cover currently observed near most TAF sites is
expected to partially clear around 16Z. Model guidance indicates
potential for thunderstorms after sunset, which will traverse
across the terminals from the northwest starting with STJ around
midnight. The cloud bases of these storms are anticipated to
remain above VFR thresholds. Winds will be substantial
throughout the daytime hours, out of the southwest at 10-20
knots with gusts possibly over 25 knots. A northwesterly wind
shift is expected overnight with frontal passage.


&&

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

&&

$$

DISCUSSION...Krull
AVIATION...Hayes