394
FXUS63 KEAX 182012
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
312 PM CDT Fri Apr 18 2025

.KEY MESSAGES...

- Thunderstorms are expected tonight, mainly south of Interstate
  70. Best chances of severe weather are to the south of the
  forecast area, but cannot rule out an isolated severe storm
  with large hail southeast of a Pleasanton to Kirksville line.

- Multiple rounds of showers and storms are expected Saturday
  through Sunday morning, especially near and southeast of I-35.
  Chances for severe weather will be low through this period.

- Another round of thunderstorms is likely Sunday afternoon.
  Severe-weather chances are higher with this round, especially
  east of the Kansas City area. Repeated rounds of rainfall may
  also cause some instances of river flooding (see Hydrology
  section below).

- After a brief dry period early next week, more chances for
  storms are apparent by midweek.

&&

.DISCUSSION...
Issued at 201 PM CDT Fri Apr 18 2025

The pattern will be quite active across the central U.S. through
much of the next seven days. Forecast challenges center on any
severe/flooding potential through Sunday, fine-tuning the
timing/geographical placement of precipitation through this
period, and after a brief break Monday into Tuesday, pinpointing
timing of precipitation potential Tuesday night onward.

A rather interesting upper-air pattern is setting up across the
CONUS late this week, with a deep/positively-tilted trough in
the Intermountain West and a broad, high-amplitude, positively-
tilted ridge downstream in the central/eastern U.S.
Southwesterly flow in the central U.S. will permit multiple
perturbations to eject northeastward from the aforementioned
larger-scale trough through Saturday night, before the main vort
max moves into/through the region on Sunday, acquiring a rapid
negative tilt as it does so. Such a pattern is recognized as one
favoring (1) a corridor of heavy rainfall (main threat of this
looks primarily south of our forecast area, though significant
QPF (2-4 inches) may occur in our far southern CWA by Sunday
night) via repeated bouts/training of convection and (2) a
notable/regional severe-weather event (tied to the main vort max
passage, which would be on Sunday).

The primary trend observed in CAMs today regarding convective
potential tonight has generally been a southward shift, which
suggests severe potential has diminished further for our
forecast area. Still cannot rule out a rogue severe storm with
marginally severe hail in our far south (primarily south of a
Pleasanton to Kirksville line), but think most precipitation
tonight will be benign. Indeed, beyond our southern CWA border
with WFO SGF, precipitation probabilities drop off rather
sharply (particularly when observing ensemble QPF). Areas
northwest of I-35 may see little precipitation at all through
tomorrow morning, while areas near/south of Pleasanton, Butler,
Clinton, and Sedalia may see totals up to an inch or more. Lows
tonight will mainly be in the 40s, in sharp contrast to
temperatures seen early this morning (mid to upper 60s).

With the southward shift in convection tonight, models are also
suggesting that it will be tougher to get precipitation farther
north into our area for much of the day on Saturday. This makes
sense, as models tend to underestimate the southward
displacement of instability, particularly when repeated rounds
of convection occur regionally. With a seemingly endless barrage
of perturbations ejecting into the Plains tonight and Saturday,
we suspect that precipitation will have a tough time progressing
northward into the forecast area for much of the day. For this
reason, we retain a rather sharp drop-off in PoPs across the
U.S. Highway 50 to U.S. Highway 36 corridors. And given such a
drop-off, rainfall totals are rather uncertain across most of
the area through Saturday. It is not out of the question (and,
in fact, fairly likely) that most areas north of U.S. Highway 36
see little or no precipitation through this time.

With precipitation chances highest in our south, a rather
unusual distribution of temperatures is forecast for Saturday,
with the highest max temps in our northern zones (upper 50s to
low 60s), with the lowest max temps south of U.S. Highway 50
(low to mid 50s). Given extensive cloud cover and repeated
rounds of precipitation, instability will be meager, and
severe-weather chances will be low Saturday and Saturday night.

Through Saturday night, the upper pattern will have evolved
considerably. The upstream deep trough will have been digging
into western Texas and vicinity, becoming more neutrally tilted
during this time. Rapid cyclogenesis will commence in the
southern Plains by Sunday morning, with widespread convection
developing within the system`s warm sector and via warm
advection to the north and northwest of the quasi-stationary
front. This latter area of precipitation will move into the
region Saturday night into Sunday morning. How this
precipitation/convection evolves will be key to what follows on
Sunday afternoon. Given how quickly the system acquires a
negative tilt Sunday morning, the previously mentioned quasi-
stationary front should surge northward as a warm front quickly
through the central Plains during the day, taking much of the
warm-advection precipitation with it. The 12z NAM Nest (among
other longer-running CAMs) shows this process well, developing
a narrow corridor of diabatic heating immediately in advance of
the system`s cold front/dryline. With intense large-scale ascent
nosing impinging upon the front/dryline, little heating will be
required to generate widespread and vigorous convection by
midday or shortly thereafter. Proximity soundings in immediate
advance of the front/dryline are impressive, with deep-layer
shear well in excess of 40 kt, ample low-level SRH, and thin but
deep CAPE profiles. Along with the overall setup, these
ingredients indicate a very favorable severe-weather
environment. In coordination with the SPC, the Day-3 outlook now
covers most of the CWA in at least a marginal risk, with an
enhanced risk now in place in central Missouri. The overall
setup is favorable for all severe hazards, but will be
contingent on how quickly the immediate downstream environment
recovers and subsequently destabilizes after the overnight
convection. Nevertheless, the strong agreement amongst
deterministic/ensemble solutions at this range suggests that the
severe potential appears to be increasing markedly on Sunday.
For the KC area, another two factors will be important: the
timing of initiation and the speed of the front/dryline surge.
Consensus would suggest probabilities for severe weather are
much higher to the east of the metro, but any trend toward
slower eastward progression would put the metro in play.

Meanwhile, this final round of convection Sunday afternoon will
have led to a period of 2-4 inches of rainfall in our far south.
This will be enough to produce some instances of river flooding;
however, at this time, most flooding would appear to be minor
and/or of the nuisance variety.

The low and attendant negative-tilt trough blast northeastward
Sunday night and Monday, leaving the region in quasi-zonal upper
flow. A brief dry period should result Monday into Tuesday.
However, most guidance is quick to return the upper flow to a
more southwest-to-northeast orientation by midweek. Additional
vorticity maxima should progress into the Plains with a wide
open Gulf in play. Additional rounds of convection appear
probable Tuesday night into the rest of next week. For now, have
broad-brushed 30-65 percent PoPs for much of this period, with
model timing uncertainty not allowing for much fine-tuning at
this stage.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1225 PM CDT Fri Apr 18 2025

Some brief showers are moving through the area early this
afternoon, and have provided somewhat variable ceilings and
winds for short periods of time as they have moved through. Most
of these showers should be east of the terminals by 19z. MVFR
ceilings will continue this afternoon, though there is a >50
percent chance of a period of VFR between 22z and 05z at the TAF
sites. As convection develops to the south this evening and
tonight, some periods of showers may approach the TAF sites
after 05z. Better chances of thunder are to the south of the
terminals, though chances are high enough for TAF mention at
IXD. A brief drier period may occur again after daybreak
Saturday. Oscillations between VFR and MVFR are probable between
05z and 18z Saturday as well, with TAF amendments likely during
this period.

Winds will generally be from the northwest or north this
afternoon around 10 kt, slowly veering to the north-northeast
tonight and Saturday.

&&

.HYDROLOGY...
Issued at 201 PM CDT Fri Apr 18 2025

Periods of showers and thunderstorms tonight through Sunday are
expected to lead to two to four inches of rainfall mainly south
of I-70. This rainfall could lead to rises along area streams
and rivers, especially the Blackwater and Lamine Rivers as well
as Big Creek in the vicinity of Blairstown. Ensemble guidance
indicates at least some potential for minor flooding on the
Petite Saline, the Marais Des Cygnes (at La Cygne), and Moniteau
Creek at Fayette, as well. However, considerable uncertainty
remains with rainfall totals, with a sharp drop-off in
accumulations on the north side of the precipitation shield
anticipated. As a result, the flood watch remains unchanged at
this time.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch from 7 PM CDT this evening through Sunday evening
     for MOZ045-046-053-054.
KS...Flood Watch from 7 PM CDT this evening through Sunday evening
     for KSZ060.

&&

$$

DISCUSSION...CMS
AVIATION...CMS
HYDROLOGY...CMS/BT