-- Discussion containing changed information from previous version are highlighted. --
393
FXUS63 KEAX 211737
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
1237 PM CDT Fri Jun 21 2024

.KEY MESSAGES...

- Warm and Humid This Weekend

- Showers/Storms Saturday Night; Some Strong to Severe Possible

- Potentially Dangerous Heat and Humidity Start of Next Week

&&

.DISCUSSION...
Issued at 327 AM CDT Fri Jun 21 2024

Today through Sunday Night:

Amplified ridge expanding from the Gulf Coast into the lower
Missouri River Valley has been providing warm and humid conditions
across the region the past 24 hours with surface cyclone now
centered over the Ohio River Valley and another centered over the
northern Great Lakes Region. Stronger southwesterly flow with a few
short-wave perturbations and vort maxes has been pushed northward
around the ridge, and has kept more robust thunderstorm activity
over the Northern Plains and far upper Midwest. A high theta-e
boundary layer across eastern Kansas and Missouri though may support
a few pulse showers/storms Friday morning into the early afternoon
hours, especially with dewpoints in the upper 60s to lower 70s and
temperatures in the upper 80s and lower 90s. There is some weak dCVA
over the front range prompting a weak surface pressure fall response
that may provide some convergence into the eastern Plains, but
overall forcing is weak and kinematics weak that will prevent any
true organization. As of 06z, the CAMs, particularly the HRRR, has
backed off any substantial activity. The 00z HREF mean QPF is just a
fews hundredths of an inch scattered about the western third of the
CWA. Synoptic scale ensembles through late this afternoon do not
show a robust signal for much precipitation. Thus, will only
maintain slight chance POPs through this afternoon. As for
temperatures, southwesterly 925mb-850mb winds will continue to
provide strong WAA across the area, while at the surface southerly
winds will continue to supply Gulf moisture to the area. We could
see dewpoint readings in the lower 70s in some locations, though may
not last overly long if we see some mixing later into the afternoon.

Saturday, mid-level vort max ejects out of the Rockies across
Central Nebraska. The bulk of the mid-level forcing with this tracks
north of our area through Iowa, but dCVA will be strong enough to
promote surface lee cyclogenesis through the afternoon that will
slowly increase lower-level convergence Saturday as H5 heights
slightly drop and attempt to deamplify the large ridging pattern.
Southerly surface flow should continue to provide a rich theta-e
boundary layer airmass across the lower Missouri River Valley
Saturday afternoon. Drier air between 850-700mb should result in an
EML that keeps a stronger cap in place through the late afternoon
hours. However, attention then turns to a cold front that trails the
surface cyclone moving across the central Plains that should provide
enough forcing to break the cap, pushing up a on boundary layer with
temperatures in the lower to mid 90s and dewpoints in the lower 70s.
In addition, compact jet streak may increase deep layer shear
especially for areas north of U.S. Highway 36 later into the evening
on Saturday that could provide 0-6km bulk shear values between 30-40
kts. This along with MLCAPE values above 3000 J/kg should support
organizing convection later into the evening on Saturday, and could
pose a threat for strong to severe storms. At this time, still tough
to pinpoint exact hazards, as mid-level lapse rates remain uncertain
with how much mid-level cooling may occur. Currently, deterministic
GFS and NAM soundings suggest weak warming in the mid-levels that
could hinder robust lapse rates, and further backing of 850mb-700mb
winds may introduce some moisture that while helping to erode the
cap (especially with preceding daytime heating) may erode steeper
low-level lapse rates that were in place with the previous EML.
Therefore, hail threat may be questionable with weaker
thermodynamics. Depending on the degree of boundary layer mixing and
presence of the low-level jet could still foster a wind threat, and
brief period of low-level veering hodographs could support a brief
tornado. In addition to strong/severe storms, higher PWATs and humid
airmass could lead to efficient rainfall producers that result in
flooding concerns heading into Sunday morning. Overall GEFS
probabilities for Saturday Night into Sunday morning for at least
0.10 inches of QPF are above 70 percent, with 30 percent
probabilities for at least 0.50 inches. With locally heavier
rainfall with individual thunderstorms, could potentially see some
areas see closer to 1.0 inch of rainfall. One factor helping to
mitigate higher rainfall totals will be the faster speed of the
short-wave moving through and propagation speed of the front. While
there may be some training relative to the initiating thermal
boundary, the thermal boundary itself should be progressive enough
to prevent training convection over any one particular location. The
12z HREF this morning may be able to provide details in the
probability matched mean fields for any hydro related concerns with
this system.

Sunday afternoon and evening, the front clears the area and stronger
H5 height rises resume with ridge over the Gulf Coast pushing back
northward. This will help push temperatures back into the lower 90s
Sunday afternoon, and then sets up more heat for the start of next
week.

Monday and Beyond:

Per GFS surface analysis, a robust high pressure center is observed
near the Four Corners region in the early hours on Monday. The
ridging pattern brought by this high will provide very warm
temperatures, along with a calm, upper-level northwesterly flow for
the area on Monday and Tuesday afternoon. Highs will be in the mid
90s due to the amplified ridging combined with southerly surface
winds. The large scale synoptic pattern is expected to change early
on Tuesday, as the location of the ridge axis shifts back toward the
western United States while a mid to upper-level short-wave trough
digs in from Canada into the central CONUS. This will increase
chances for precipitation on Tuesday afternoon, extending into
Wednesday. According to model guidance, the likelihood for
thunderstorms is the most substantial Tuesday evening. After the
shortwave traverses east of our area, predictable summertime ridging
again dominates the overall synoptic pattern. Late week highs
will be limited to the low to mid 80s due to a northeasterly
flow at the surface caused by the frontage passage early
Wednesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
-- Changed Discussion --
Issued at 1234 PM CDT Fri Jun 21 2024

VFR conditions are expected to remain for the duration of the TAF
period. Winds will come from the southwest and will remain fairly
weak with an occasional gust to 15 mph.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Hayes/Krull
AVIATION...Collier