816
FXUS63 KEAX 212323
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
623 PM CDT Tue May 21 2024

.KEY MESSAGES...

- Chances for strong to severe storms this afternoon and evening continue
  across MO and KS. Storms are expected to start out as
  discrete cells before merging into a line of storms. All
  hazards are possible including damaging winds, large hail, and
  tornadoes.

- Storm chances will be greatly influenced by the position of
  the cold front and timing of storm initiation. Severe risk is
  significantly reduced behind the front.

&&

.MESOSCALE...
Issued at 127 PM CDT Tue May 21 2024

Satellite imagery shows an area of agitated cumulus
overspreading much of far eastern KS and western MO.
Observations show the cold front progressing into eastern KS.
Some convection has initiated across SE Nebraska; however, the
18Z TOP sounding shows a little bit of a CAP left curtailing
development further south at this time. This CAP is expected to
erode as daytime heating continues. SPC mesoanalysis shows
nearly 1000-2000 J/kg CAPE gain in the past 3 hours mostly due
to daytime heating. Bulk shear remains above 50kts with 0-1
helicity of 100-150 m2/s2. All of these factors keep
expectations for storm modes unchanged. Initial discrete storms
are anticipated before storms congeal into a line across central
MO. All severe hazards including large hail, damaging winds,
and tornadoes are possible.

Uncertainties remain as to where the front will be when
initiation takes place; however, trends in obs and CAMs suggest
storms starting to form within the next 1-3 hours.

&&

.DISCUSSION...
Issued at 107 PM CDT Tue May 21 2024

Short Term (Today-Tonight)

A small line of elevated storms moved across far northern MO during
the morning hours. Its concentration further north and quick
progression through the region does not look to impact the short
term forecast. Warm air and moisture advection into the region
continues ahead the approaching cold front.  This destabilizes the
atmosphere substantially  with some CAMs already projecting CAPE
values around 3000-4000 J/kg. Bulk shear above 50kts and midlevel
lapse rates greater than 8 C/km further increase confidence in the
potentially volatile environment. Storms are already beginning to
form across far SE Nebraska. Now, it is just a matter of how fast
the cold front progresses across eastern KS and how long it takes
for storms to initiate across the cold front.

Confidence is high that storms will form within the warm sector
ahead of the front; however, exactly where the front will be as
storms initiate is still in question. Short term model guidance
varies in the timing of convective initiation and the position of
the front. Citing two, the NAMnest initiates convection across
eastern KS pushing eastward into central MO through the evening.
Conversely, the HRRR suggests the front progressing further eastward
with storm initiation possible along and east of the I-35 corridor.
If the cold front progresses further eastward, those behind the
front may not see any storms regardless if there are within the
outlined risk areas.

Where models have been persistently agreeing is in the expected
storm modes and evolution of the system. Confidence is high that
storms are expected to start as discrete cells before congealing
into a line of storms across central and eastern MO. These discrete
cells are expected to bring chances for large hail (2+ inches),
damaging winds, and tornadoes. These threats are expected to
continue even as storms begin to linearize. Once the line becomes
fully organized, the primary threat transitions to damaging winds.
However, embedded brief tornadoes remain possible. Please ensure you
have multiple methods for receiving weather information; especially
during the late evening hours.

Longer Term (Extended Forecast)

The long term forecast remains persistent. A reinforcing vort
max will move through the Midwest on Wednesday, which may keep
storm chances in our southern fringes during the
afternoon/evening. More likely, though, is that storms will stay
south of the region Wednesday and Wednesday night (70 percent
chance). After the warm weather today, temperatures will be much
more seasonal on Wednesday in the wake of the system.

The pattern late this week into this weekend remains unsettled,
with general quasi-zonal or southwesterly low-amplitude flow in
place. Multiple perturbations will eject from a broad large-
scale trough in the West, leading to multiple chances for
convection through the holiday weekend. Ensembles are gradually
converging on a relatively higher threat Thursday night and
Friday as well as Sunday. With an open Gulf and relatively fast
flow in proximity to the perturbations, at least some severe
threat exists with each of these passing systems. Notably, the
CSU machine-learning probabilities provide nearly daily chances
of severe weather from Thursday through Monday for the region.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 618 PM CDT Tue May 21 2024

With today`s expected storms well east of the terminals this
evening, VFR conditions are expected at all the Kansas and
Missouri state line terminals through this TAF cycle. Only issue
to watch will be the strong west wind, which will be very gusty
through 03Z, then should ease up as it veers to the northwest.


&&

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

&&

$$

MESOSCALE...Pesel
DISCUSSION...Pesel/CMS
AVIATION...Cutter