306
FXUS63 KEAX 191105
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
605 AM CDT Sun May 19 2024

.KEY MESSAGES...

- Isolated Shower/Storms Northern Missouri This Afternoon

- Congealed Convective System Late Tonight Early Monday; Conditional
Severe Wind Threat

- Severe Storms Forecast Tuesday

&&

.DISCUSSION...
Issued at 340 AM CDT Sun May 19 2024

Widespread precipitation is expected across our forecast area
starting late tonight and continuing through Monday. The severe
threat for both late tonight and throughout the day Monday are
conditional and contain high degrees of uncertainty. Overall,
ensemble probabilities for precipitation are high, over 90 percent
chances for measurable precipitation across most of the forecast
area, and most points hold around a 40 percent chance for exceeding
0.50 inches of rainfall. Synoptically, persistent mid-level
southwesterly flow with strong vorticity maxima will provide
multiple opportunities of favorable kinematics. The big
uncertainties for our area will be thermodynamic recovery from
Sunday into Monday. This will largely depend on how potential MCS
behaves Sunday Night. If our area is to see any severe winds or hail
from MCS, the MCS will be largely dependent on cold pool dynamics
maintaining it.

This morning, mid-level ridge axis has cleared the area. Low-level
flow continues to provide warm air advection into the region,
keeping temperatures generally in the mid to upper 60s, with a few
70s still being reported between 07-08 UTC. Strong PV anomaly
continues to sit over the Pacific Northwest, with a 2.0+ PVU as low
as 700mb. The troughing pattern continues, creating brisk
southwesterly flow across the Central CONUS. A stronger short-wave
and associated surface cyclone has lifted into Canada, but the
trailing cold front made it about two-thirds of the way southeast
into our forecast area before stalling. As of this morning, a mid-
level vorticity maxima has been ejecting from the Front Range into
the High Plains. This has briefly provided H5 height rises into the
lower Missouri River Valley early this morning, which has helped
stall the cold front in its current position. In western Kansas, the
dCVA associated with this vorticity maxima has resulted in surface
cyclogenesis, and has been deepening over the past few hours.
Surface pressure falls are slowly occurring eastward, and will
continue to do so through the afternoon hours, This will provide
backing to lower-level winds, and should begin to push the thermal
boundary back north as a warm front later this afternoon. With the
pressure falls expanding eastward and thermal boundary in place,
convergence may increase along the boundary for areas primarily
north of Hwy. 36 this afternoon which could force a few showers or
even thunderstorms. With flow southwesterly between 700-600mb, an
EML will likely be present this afternoon above the boundary layer,
which will result in steep lapse rates. If the subtle height rises
through this morning are enough to keep skies clear, boundary
layer destabilization could support a few stronger updrafts
along the warm front. However, the better kinematic support for
deep layer shear will still be much further west over Central
Kansas. This will make it difficult for storms along the warm
front this afternoon to organize, thus limiting the severe
threat. The stronger EML may also result in capping of near
surface parcels, thus limiting severe potential this afternoon
in our northern CWA. The main concern for Sunday Night into
early Monday morning will be how convection over Central Kansas
evolves. Over the Central Plains, the EML will be quite strong,
along with robust boundary layer mixing in the presence of
deepening surface cyclone. Dryline will also be in play in far
western Kansas late this afternoon. Plenty of sources of low-
level convergence in the Central Plains for initiation of
storms. With drier air aloft and stronger boundary layer mixing
creating inverted-v soundings in the lowest part of the
troposphere, along with increasing wind shear with the mid-level
vort max, convection likely congeals as low-level jet ramps up
and allows strong segments, with some bowing structure to it, to
develop in Central Kansas. Over the Central Plains, CAPE should
be high enough to support this for a bit. However, CAPE values
quickly dwindle after sunset from far eastern Kansas into
Central Missouri. HREF mean SBCAPE values are just a tad under
2000 J/kg by 0400z, and by 0600z, when the favorable kinematics
and mid-level vort max are passing through, mean HREF CAPE
values are under 1000 J/kg which generally would not be
favorable for supporting a late Spring early Summer time MCS.
However, if the shear and MCS cold pool vorticity remain in
balance, the system could continue into our area. Current
downshear Corfidi vector estimates indicate a strong healthy MCS
could be moving at 50+ kts. Propagation speed alone could get
near severe criteria for wind gusts. With that being said, this
is all conditional on an MCS holding up. CAM guidance since 00z
indicates the MCS breaking down as it crosses the Hwy. 75
corridor, essentially as it outruns its instability axis. HREF
QPF mean values quickly drop-off as it enters our area as well.
Simulated radar reflectivity fields appear to indicate the
system becoming outflow dominant into the early morning hours of
Monday, which would greatly limit the severe threat with the
system. Overall, current feeling is that it is a 50/50 coin toss
on how organized this system is as it rolls through. Will need
to watch trends closely through the afternoon, and radar
observations may be the best indication. If the system breaks
apart and does not materialize the wind and hail threats, we may
still see efficient rainfall that could present some hydrology
issues, especially if the system slows down. However, HREF does
not provide much concern with hydro though, as probability
matched mean QPF values have a few pockets of 1.25 inches, with
widespread 0.75 to 1.00 inch elsewhere. Most areas should be
able to handle this, as long as it is spread out over a period
of a few hours.

Monday late morning and through the afternoon, H5 vort max should be
exiting the area, moving favorable kinematic forcing out of the
area. There is still potential for lingering precipitation from
overnight MCS to be ongoing. Another short-wave trough and vorticity
maxima ejects out of the Front Range will the PV anomaly still sits
over the Northern Rockies Region. This will provide more deepening
for the surface cyclone in western Kansas and should enhance
southerly flow into the lower Missouri River Valley. This will
provide stronger theta-e advection and send surface dewpoints into
the upper 60s across most of the forecast area. The short-wave
trough will briefly provide H5 height rises at some point on Monday
which should limit large scale ascent through the afternoon.
However, will need to keep an eye out on outflow boundary activity
across the area left over form remnant MCS, and may need to remain
on the lookout for remnant MCV that could greatly modify the
mesoscale environment. Perhaps stronger differential heating along
one of these boundaries provides a greater source of convergence
that can overcome the lack of large scale synoptic ascent through
the afternoon, and locally increase wind shear. Some model guidance
does destabilize the boundary layer again, resulting in MLCAPE
values near 2500 J/kg. If new initiation occurs Monday afternoon
into evening, there would be potential for a few severe storms.
However, this is very conditional, thus leading to low confidence in
the occurrence of severe weather. There are several possible
mesoscale scenarios that could evolve on Monday.

Tuesday remains to be the most robust synoptic scale support our
forecast area will have through this multi-day stretch of convective
activity. A stronger short-wave trough and robust vorticity maximum
ejects out of the Front Range and phases once again with surface
cyclone over the High Plains. The PV anomaly over the Pacific
Northwest is finally progged to start moving eastward with broader
jet streak developing, moving the system further east. The short-
wave trough begins to develop a negative tilt and lifts into the
Central Plains by mid-afternoon. As the cyclone shifts eastward,
surface pressure falls become more rapid and will start to back
surface winds into the lower Missouri River Valley, and provide
stronger theta-e advection into our region. There is still
uncertainty with how early the trough begins to lift and where this
will place the best mid-level kinematic support, but overall ascent
will be widespread across the Central CONUS that it should bring
stronger storms to much of the area. With 700-600mb flow
transporting a stronger EML into the region, mid-level lapse rates
will steepen through the afternoon. Model soundings indicate this
combination along with boundary layer destabilization to yield
MLCAPE values potentially in excess of 3000 J/kg, and amongst NBM
members holds a 50 percent chance to achieve this. If the jet streak
approaches our area, the warm sector could experience 0-6km bulk
shear values between 50-60 kts. A cold front will start moving
across the Central Plains during this time, further increasing
convergence across our area. This may be enough develop a few
discrete storms across a strong warm sector Tuesday afternoon into
early evening, especially if the trough does not lift too early
providing stronger synoptic scale ascent. Overall veering wind
profile and longer, looped, hodographs could support a few
supercells capable of damaging winds and large hail. A conditional
tornado threat could be realized if the surface winds acquire a
southeasterly direction, providing better potential for low-level
streamwise vorticity ingest. It is still a bit far out to call for
this though, and will need to monitor how Monday activity, if any,
alters the environment. If the trough starts to lift early and
synoptic scale ascent is not as strong, then convection initiation
on Tuesday will have to wait a few more hours until the cold front
comes through and pushes up on the warm unstable boundary layer. In
this scenario, deep layer shear is still strong but the vector is
oriented parallel to it, resulting in quick upscale growth. However,
the strong kinematics and stronger mid-level lapse rates could
provide potential for a few stronger bowing like segments along the
cold front, presenting a damaging wind threat with potential for
strong vertical pressure perturbation gradients to develop. The vort
max is progged to clear the area by late Tuesday Night into early
Wednesday morning, with the cold front surging ahead and strong
surface anti-cyclone moving in behind it. As for hydro issues, the
system will likely be progressive enough, but, if heavier rainfall
occurs with Monday convection, may start to see some flooding
issues. Current ensembles though keep greater QPF and excessive
rainfall potential further north of our area closer to the warm
front. Along the cold front, while training storms in a boundary
relative sense are possible, the front should likely be progressive
enough to limit this threat.

Wednesday should see a brief break from precipitation and
thunderstorm activity, but more short-waves are possible toward end
of next week with elevated probabilities for accumulating rainfall.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 555 AM CDT Sun May 19 2024

VFR conditions will continue through 00z Monday, with variable
winds this morning becoming predominantly southeasterly this
afternoon and increasing to 10 to 15 kt with occasionally higher
gusts. Convection will develop to the west this afternoon and
attempt to move into the area around or after 03z. Uncertainty
is quite high regarding the intensity of these storms, but
confidence is increasing regarding at least some direct impacts
at the terminals in the 03z to 06z time frame (probabilities
around or above 50 percent). Additional storms may develop
after 06z, but confidence is much lower with this potential --
think a PROB30 mention is prudent for now.

&&

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

&&

$$

DISCUSSION...Krull
AVIATION...CMS