298
FXUS63 KEAX 171116
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
616 AM CDT Sat May 17 2025

...Updated 12z Aviation...

.KEY MESSAGES...

- Quiet Weather Through Saturday Late Afternoon

- Rain Showers and Thunderstorms Sunday; Conditional Severe Threat

- Severe Thunderstorms Expected Monday, Tuesday Threat Shifted
  Southeastward

- Heavy Rainfall Likely Leads To Flooding Issues Monday and Tuesday

&&

.DISCUSSION...
Issued at 350 AM CDT Sat May 17 2025

Closed-low system is starting to move into the Northern Great Lakes
Region. An area of mid-level troughing over the eastern Pacific and
another area of troughing near the Baja Peninsula have prompted an
H5 height rise response across the Central CONUS through the
overnight hours that will eventually lead to a ridge axis passing
through the area. Subtle dCVA starts in the Front Range into the
Texas Panhandle this afternoon that will kick off surface
cyclogenesis broadly across the High Plains. This keeps low-level
flow southerly and southwesterly from the southern Plains into the
lower Missouri River Valley for Saturday, helping to amplify the H5
heights. This thermal ridge axis passes through, brining
temperatures back into the upper 70s and lower 80s, even after the
passage of the cold front trailing the closed-low system well north
of the area from last night. May see a few clouds this afternoon
with some upper-level moisture that moves through but most of this
should move east, and subsidence with the H5 height rises should
lead to mostly sunny conditions across our forecast area, for the
exception of far northern Missouri which may see lingering cloud
cover. By late evening, the trough axis over Pacific accelerates
inland and phases with the with southern trough axis, strengthening
dCVA and surface cyclogenesis over the Front Range. Stronger theta-e
transport occurs across the southern Plains into the eastern Plains
of Kansas, along with the warm front surging northward. Expecting to
see isentropic upglide as this moves northward, and will be enough
to generate rain showers and perhaps isolated thunderstorm activity
into our southwestern forecast area, and could clip portions of the
KC metro. H5 level will still largely be characterized  by a ridging
regime which could hinder lift with the surging warm front, but CAMs
are showing some hints of a few localized, though weak, vort maxima
moving through. LLJ development could increase some convergence, but
overall forcing and kinematic support is not impressive, therefore
not expecting activity late tonight and very early Sunday morning to
pose a severe risk. That risk will likely remain along and south of
the U.S. Hwy. 400 corridor.

Sunday late morning through afternoon, deep H5 trough axis and
associated jet streak heads toward the High Plains that will begin
to lift the trough, acquiring a negative tilt as Sunday afternoon
progresses. The dCVA across the High Plains drastically strengthens
at this time, and expecting a maturing cyclone to begin moving
eastward. Strong WAA along with favorable moisture transport occurs
from east-central Kansas to the middle Mississippi River Valley,
with warm front surging toward the Iowa-Missouri state line and
pushing primary H5 ridge axis completely across the area.
Deterministic guidance solutions still demonstrate some discrepancy
with how far north this boundary eventually travels, continuing some
uncertainty with how the mesoscale environment exactly evolves.
Strong mixing over the High Plains of Kansas will allow a dry line
to propagate from western Kansas into Central Kansas through the
afternoon, and CAMs continue to favor strong convergence along this
feature as it pushes up against a high theta-e airmass east of
Interstate 135/U.S. Hwy. 81. Across central and southeastern Kansas,
surface troughing extends eastward and mid-level vort maxima eject
from the primary trough, which begins to stall over the High Plains
of Nebraska as it attempts to close-off. Convection initiation from
central Kansas to east-central Kansas is depicted between 18z-21z in
the HRRR along with a few other CAMs. However, the eastward mixing
of the dryline is still not consistent amongst all available
guidance, and the surging of the warm front is also playing a factor
in where the favorable forcing/convergence along a dry line
encounters a favorable segment of the ambient warm-sector. Once
convection does get going in eastern Kansas, 0-6km bulk shear values
of 30 kts should allow updrafts to organize efficiently, oriented
perpendicular to the dryline feature. This can favor a discrete
storm mode in eastern Kansas, with the shear environment supporting
supercell development. If convection takes longer to initiate and is
closer to the onset of the LLJ, discrete storm mode may not last
long, and congeal more into an MCS like feature. This eventually
will start to move toward western Missouri into our forecast area.
Our counties should have plenty of moisture by this time, with
dewpoints pushing into the 60s, and expecting MUCAPE values to start
to push above 3000 J/kg. However, areas along the Kansas-Missouri
stateline still appeared capped, with most areas around -100 J/kg
CIN within the area of favorable forcing. While eastern Kansas may
see quite a bit of activity, where the enhanced risk is in the
SWODY2 outlook, initiation may not be possible in Missouri. Current
thinking is that any activity that makes it to Central Missouri may
come in the form of an organized MCS of some kind that initiates in
Kansas and is then able to sustain itself as it encounters a capped
environment through Missouri. The wild card for forcing will be if
the dryline feature can continue to mix eastward and provide enough
convergence to break through the cap in western Missouri. Therefore,
thinking damaging wind gusts and hail would be the primary threat if
a stronger MCS is able to materialize. Low-level shear environment
could support a tornado, but the only way for this to happen is if
the currently expected cap erodes and our area is able to achieve CI
of discrete storms. Therefore, this makes any probabilities for
tornadic activity on Sunday extremely conditional from the state KS-
MO stateline and eastward. Fine mesoscale details will largely
determine the eastward extent of severe convection for Sunday
evening and very early Monday morning.

Monday, higher confidence in the occurrence of severe thunderstorms
across much of the area, but still uncertainty with respect the
primary hazard and dominant storm mode for the day. Although H5
trough transitions into a closed-low system, most of the flow across
the area remains southwesterly, continuing theta-e transport into
the entire lower Missouri River Valley. Still uncertain as to where
the warm-front surges to, and where it may eventually stall. Surface
cyclone will be making progress across Kansas during this time, a
corridor of surface pressure falls and troughing extending eastward
as far as eastern Missouri and western Illinois. Multiple mid-level
vort maxima should eject from the main trough over the Plains,
providing broadscale lift over the warm sector, while nose of H5 jet
streak works toward Missouri, and at some point during the day most
of the area experiences the left-exit region of the jet streak.
SBCAPE values are progged to climb above 3000 J/kg, with dewpoints
climbing into the upper 60s and perhaps even lower 70s. Additional
convergence should occur as cold front moves across Kansas trailing
the surface cyclone. There will be two areas of interest with this
system. The first will be the warm front, which likely coincides
with area of surface pressure falls through the afternoon hours of
Monday. With passing mid-level vort maxima and increasing deep layer
shear, discrete cell development if achieved will have a favorable
shear environment for the development of supercells. Directly along
the warm front, backing surface winds should cyclonically curve low-
level hodographs sufficiently to help develop low-level mesos, and
approaching H5 jet streak should lengthen mid and upper-level
portions of the hodograph, allowing discrete storms to easily
organize. In this environment, all modes of hazards are possible.
Depending on how expansive the warm-sector becomes, there may be
enough lift for stronger storms to develop south of actual warm
front that could also produce multiple hazards with extensive
tracks across the warm sector. Failure mode for this scenario would
be if the timing of boundary layer destabilization and mid-level
lift do not line up. Next opportunity, will be along the cold front.
There may be a short-window where the deep layer shear vector is
perpendicular to the cold front, allowing for additional discrete
development. Depending on where against the warm sector this would
occur will determine what the low-level wind shear profile looks
like, and therefore also controls tornado threat with this. If cold
front initiated storms ingest more cross-wise vorticity, this may
end up being more of hail and wind threat. Eventually, Monday
evening low-level jet develops, and if there are any discrete
storms, likely congeal into an MCS. Deep layer shear vectors become
more parallel to the cold front late Monday, further supporting
upscale growth. The 00z CAMs that run tonight may give us better
insight into potential storm mode evolution as their output will
start to cover most of the activity for Monday. Perhaps by this time
too, there will be better consensus on the warm front position.
Hydro will also be a problem starting Monday, with PWATs still above
1.5 inches across most of the forecast area. A stalled boundary
could result in training storm potential, especially if multiple
short-wave perturbations move across the warm-sector. Rainfall rates
of 1 to 2 inches per hour may become possible, resulting in flash
flooding and river flooding as well. What areas this impacts will
also be determined by where the warm front eventually positions.

Tuesday, cold front should start to push through the area, though
there is still some uncertainty which how the H5 closed-low
behaves. We still have quite a bit of large scale ascent, along with
convergence with both cold front and surface cyclone. What lingers
from Monday will control how much instability is left-over, and how
quickly the environment recovers by Tuesday morning and afternoon.
Biggest question, how far west is there a threat for strong to
severe storms on Tuesday. Some ensemble members keep probabilities
west of the Kansas City metro, while others push stuff east of Hwy.
65. At this time, will not dive much into potential mesoscale
outcomes with Tuesday, but be prepared for another round of severe
storms, or for Monday activity to continue much of Tuesday morning.
Additional rainfall will further augment flooding concerns. Beyond
Tuesday, cold front clears the area, but additional area of weak
forcing through the end of next week may bring additional
precipitation chances.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 613 AM CDT Sat May 17 2025

A few upper-level clouds may be spotted today, but ridge moves
through that should keep skies rather clear. Weaker pressure
gradient today keeps winds mostly calm. Showers and
thunderstorms may move in from southeast Kansas very late
Saturday Night and could pass by the KC metro terminals. For now
will throw showers into a PROB30 group. Sunday and Monday will
be active with multiples rounds of rain showers and
thunderstorms.

&&

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

&&

$$

DISCUSSION...Krull
AVIATION...Krull