181
FXUS63 KEAX 050415
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
1115 PM CDT Tue Jun 4 2024

.KEY MESSAGES...

- Thunderstorms are expected this evening in much of the area
  (50 to 85 percent chance). Severe storms cannot be ruled out,
  with damaging winds and marginally severe hail the main
  threats.

- Dry and near-seasonal temperatures expected through the rest
  of the work week.

- Chances for storms return this weekend.

&&

.DISCUSSION...
Issued at 259 PM CDT Tue Jun 4 2024

Main forecast challenge remains the threat of severe weather
this evening.

A vigorous upper-level trough is moving through the northern
Plains this afternoon, with a surface cold front moving
east/southeast, extending from western Minnesota to northern
Kansas early this afternoon. A few storms have initiated near
the boundary in central Kansas, in advance of a weak
perturbation moving into the central/southern Plains and along
the northern periphery of moderately to strongly unstable air
(2000-3000 J/kg MLCAPE) and in the wake of an instability
minimum in portions of the CWA (via a departing MCV). CAMs
increase coverage of convection gradually through the evening
hours, though how quickly and to what extent remains rather
variable. Recent HRRR simulations are relatively aggressive,
producing scattered convection in northeast Kansas and northwest
Missouri through much of the evening before a somewhat more
organized broken line of convection moves through the CWA later
in the evening. The 12z NAM Nest is similar, though a little
more skittish on convection through mid evening.

One limiting factor to a more substantial severe threat is the
marginal shear in place (e.g., 0-6 km bulk shear < 30 kt). With
low-level winds remaining weak, the tornado threat is quite low;
however, dry midlevels and modest midlevel flow may permit the
development of strong wind gusts with the strongest convective
cores. Additionally, substantial instability should permit the
development of hail in the strongest cores (given what we are
observing to the west), particularly if convection remains
somewhat discrete. The greatest severe threat appears to be from
7 to 11 pm this evening, as the front moves into the CWA and
more substantial instability remains. The severe threat should
gradually diminish with time late in the evening/overnight as
nocturnal stabilization increases and convective outflow becomes
dominant.

The front will sweep through the CWA overnight, with any
precipitation exiting to our south and east by daybreak. The
remainder of the week will be dominated by northwest flow and a
surface high shifting southeastward through the Plains. This
should result in a dry/seasonal/pleasant period for the region.

Eventually, a midlevel ridge in the western U.S. will progress
into the Intermountain West, providing a more favorable track
for ejecting perturbations riding the ridge southeastward into
the Plains. Meanwhile, the surface high should move well to our
southeast by the weekend. This is a setup favorable for MCS
development in the warm season. Models are beginning to
converge on the first of such events occurring Friday night into
Saturday (e.g., the 12z GFS and CMC). The pattern is low-
predictability owing to the low amplitude of the overall upper
flow and potential convective augmentation of the midlevel
vorticity maxima. Nevertheless, with the increasingly favorable
overall pattern, think mention of low-chance (below 40 percent)
PoPs is warranted Friday night and Saturday. Subsequent
perturbations may track farther south (as suggested by
deterministic models), so PoPs are lower later in the weekend.
However, considerable modification to the forecast may occur
given the aforementioned low predictability.

Forecast uncertainty increases further next week as models
diverge in their handling of a weak upper low within the broader
upper ridging to our west. In the evolving pattern, would think
precipitation chances gradually increase, though specific timing
is quite uncertain at this point. Of higher certainty is the
continued near-seasonal temperature forecast given the lack of
high-amplitude ridging and the periodic chances of storms this
weekend onward.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1114 PM CDT Tue Jun 4 2024

VFR conditions are expected to persist through the TAF period.
Showers and thunderstorms are expected to continue to move east out
of the region by early Wednesday morning. Winds will come from the
north and then switch to the west by Wednesday afternoon. Winds are
anticipated to remain light with the occasional gust to 20 knots
with diurnal mixing.

&&

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

&&

$$

DISCUSSION...CMS
AVIATION...Collier