709
FXUS63 KEAX 101033
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
533 AM CDT Wed Jul 10 2024

.KEY MESSAGES...

- Isolated to scattered thunderstorms are forecast to develop
  this afternoon into tonight in much of the region. An isolated
  strong to severe storm is possible, with strong wind gusts the
  primary threat.

- Another round of isolated thunderstorms is possible (<30
  percent chance) on Thursday afternoon and night.

- Increasing heat and humidity are expected late this week into
  early next week. Heat indices exceeding 100 degrees are quite
  probable (>90 percent chance) by Sunday and Monday.

&&

.DISCUSSION...
Issued at 237 AM CDT Wed Jul 10 2024

A deep trough in the Midwest is forcing the remnants of Beryl
quickly northeast away from the central U.S. early this morning,
but a kicker shortwave trough is digging southward through the
Dakotas and Minnesota. Associated lift with this system is
promoting convection in this area overnight and is a harbinger
of what is to come for much of the central Plains this
afternoon and evening. Short-range models continue the
progression of this perturbation south-southeastward today,
roughly in vicinity of eastern Nebraska and southern Iowa by
00z Thursday, as it begins to pivot in a more east-southeast
direction.

Given its favorable timing near peak heating and fairly strong
lift via differential cyclonic vorticity advection, isolated to
scattered convection should readily develop during the afternoon
to our north, gradually progressing south-southeastward through
the evening hours, in an environment characterized by steep
low-level lapse rates and inverted-v boundary-layer profiles and
cooling midlevels from the increasing ascent aloft. SBCAPEs of
1000-2000 J/kg should be common in advance of the perturbation
during the afternoon. Wind profiles will be generally weak
through the troposphere, with deep-layer shear of 20-30 kt.
These characteristics suggest primarily pulse-type convection,
with briefly strong updrafts associated with the most vigorous
storms. The strongest convective cores may be capable of
producing strong to locally severe wind gusts, though a lack of
stronger winds aloft should preclude increased
organization/frequency of the overall threat. Convection-
allowing models (CAMs) have tended to keep convection going well
into the evening, which suggests that the larger-scale forcing
may be sufficiently strong to keep probabilities of
precipitation mentionable through the overnight hours (similar
to what is being observed in the northern Plains early this
morning).

The main perturbation shifts eastward of the lower Missouri
Valley on Thursday, but a larger-scale trough should linger in
much of the Midwest. There are subtle hints of a weaker
perturbation shifting southeastward during the afternoon in the
Upper Midwest. This perturbation and the lingering cooler air
aloft may be sufficient to initiate convection in the region
again Thursday afternoon/evening. Given the weaker look to the
overall forcing, would expect convective coverage to be less
than that expected on Wednesday. Nevertheless, did increase PoPs
for much of the region Thursday afternoon and evening given
model soundings looking sufficiently unstable and uncapped
during peak heating. The overall environment is similar, with
pulse-type convection favored.

By Friday, the amplified ridge in the western U.S.
builds/expands eastward, encompassing most areas west of the
Mississippi River by Saturday. The ridge becomes quite prominent
by late in the weekend into early next week, with our next round
of hot/humid weather becoming fully entrenched during this time
period. Forecast temperatures remain quite hot (mid to upper 90s
by Sunday), with heat indices easily exceeding 100 Sunday and
Monday. Forecast temperatures/heat indices on Monday easily
exceed advisory criteria, and if current trends continue,
headlines look like a good bet in future forecasts.

The forecast becomes more uncertain by the end of the seven-day
period, however. The northwest flow downstream of the ridge
begins to dig a little more noticeably into the Great Lakes and
eastern U.S. by this time. Several perturbations will traverse
this faster flow from the southern Canadian prairies
southeastward. By next Tuesday, these perturbations may begin to
influence the larger-scale trough sufficiently to force the
ridging farther west. This could even bring a front and
attendant threat for convection close to or even through the
area by midweek. Model variability is pretty high by this point,
but there are tell-tale signs that this next round of heat may
not last too long into next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 528 AM CDT Wed Jul 10 2024

Aside from some patchy/transient fog at STJ early this morning,
VFR is expected at the TAF sites today. Isolated to scattered
thunderstorms are expected to develop this afternoon primarily
east of the TAF sites. However, later in the evening, more
storms are forecast to develop to the north, potentially moving
into the St. Joseph and KC areas after 03z. Have included PROB30
groups for this potential, roughly in the 03z to 09z period.
Outside of convection, VFR should continue overnight. Winds
today will become northwesterly 5 to 10 kt, before becoming
light and variable tonight.

&&

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

&&

$$

DISCUSSION...CMS
AVIATION...CMS