499
FXUS63 KLMK 161745
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
145 PM EDT Sun Jun 16 2024

.KEY MESSAGES...

*   Persistent early season heat wave expected, with highs well into
    the 90s each day.

*   Heat index values not expected to reach advisory levels, but
    societal impacts are likely.

*   Spotty coverage of afternoon thunderstorms today through
    Tuesday, then dry from Wednesday into next weekend.

&&

.UPDATE...
Issued at 1253 PM EDT Sun Jun 16 2024

Very warm and increasingly humid conditions are noted early this
afternoon. A notable low-level moisture gradient exists from SW to
NE across the region. More humid air is gradually filtering in from
the southwest, and sfc dewpoints have risen into the lower 70s in
south-central KY and many areas west of I-65. Portions of the
western and southern CWA will see at least a 2-3 hr period this
afternoon and evening with heat index values near or slightly
exceeding 100. Issued a Special Weather Statement valid through 23Z
for the elevated heat and humidity (where confidence was highest in
100+ heat index for at least 2 hours).

Otherwise, starting to finally see a cu field develop in Middle TN
where PW values exceed 1.6 inches. The hot and humid conditions will
result in 3000+ J/kg MLCAPE this afternoon across Middle TN and
southern KY. There is notably warm air in the mid-levels associated
with the ridging aloft that is limiting mid-level lapse rates. But
low-level lapse rates will continue to steepen this afternoon with
relatively high LCLs and DCAPE above 1000 J/kg. Given the moist,
increasingly unstable low-level airmass, any isolated thunderstorm
that develops will be capable of very gusty winds and brief heavy
rainfall. However, forcing is lacking. Some notable CAMs, including
the HRRR, how hold off any convective development in south-central
KY until mid to late afternoon. With forcing absent, expect
convection to remain spotty and largely confined to south-central KY
late in the day. Still expect at least a few gusty storms we`ll need
to keep an eye on later today.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 330 AM EDT Sun Jun 16 2024

Today, an upper ridge remains over the eastern CONUS while a closed
upper high sits over the Southeast. At the surface, a surface high
will get pushed, by the upper ridge, through New England before
reaching the coast. This will cause easterly winds over the CWA to
veer towards the south before continuing to the southwest. This
southern component of the low level flow will really begin to funnel
Gulf of Mexico moisture into the Ohio Valley.

By midday, precipitable water values of over 1.5" will begin
entering the CWA from the southwest. This low level moisture is
expected to produce cumulus over the region this evening, and as
some disturbances work around the upper high, this could kick off a
few isolated to scattered thunderstorms, mainly across south central
Kentucky. Some subsidence in the mid-levels could limit thunderstorm
growth. Heavy rain, lightning, and gusty winds will be possible, but
most will just experience a hot sunny day as coverage will be
limited. The warm air advection will help mostly sunny skies lift
highs into the low to mid 90, and with dew points in the mid 60s to
around 70, heat indices will climb into the mid to upper 90s. A
couple sites could reach 100. The best chances will be across the
western half of the CWA.

Tonight, southern winds will ease as precipitation chances decrease.
Skies will remain partly cloud. Lows are expected to drop into the
upper 60s to mid 70s.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 330 AM EDT Sun Jun 16 2024

Hot temperatures are expected through the week as anomalously strong
upper ridging remains anchored over the eastern CONUS. Monday and
Tuesday will be more of our traditional Ohio Valley heat, as the
ridge is centered mainly over Virginia and the Carolinas. Deep
southerly flow into the Ohio Valley will keep dewpoints near 70, and
support mainly diurnal showers and storms, though coverage will only
be isolated to widely scattered. Will carry 20-30% POPs each
afternoon.  Temps will reach the lower-mid 90s, with heat index
values near 100.

Wednesday through Friday, the strengthening East Coast ridge takes
on more of an east-west orientation, resulting in height rises and
mid-level subsidence over the Ohio Valley. This will keep a lid on
convection, and allow temps to climb into the mid/upper 90s. Still
not going too crazy with the heat index, as the warming will be
offset by dewpoints dropping into the lower 60s by Thu-Fri. It`s
nothing you`ll mistake for the desert, but just enough to take the
edge off the heat.

Rain chances return to southern Indiana next weekend, as the ridging
starts to show weakness across the Great Lakes. POPs still only
around 20 percent, and even less across Kentucky, but we`ll keep an
eye on that for some break in the heat and potential developing
drought.

Confidence in reaching triple-digit heat indices is not high enough
for even a duration-based Heat Advisory. However, a prolonged period
of hot temperatures is very likely to cause societal impacts, so we
will ramp up messaging to core partners and be prepared to go with a
Heat Advisory if confidence in broader impacts increases.

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 144 PM EDT Sun Jun 16 2024

Prevailing VFR conditions likely. SCT cumulus near 5 kft will
continue to expand north from Middle TN this afternoon, with clouds
thinning after sunset. Scattered convection is possible after 19Z
this afternoon in south-central KY, but coverage will be spotty
which limits confidence for TSRA mention in the BWG TAF. Suppose RGA
could also see a rogue shower or storm this evening, but confidence
is even lower that far north. Any storm near BWG this afternoon and
evening could produce brief heavy rainfall, resulting in IFR/MVFR
visibility. Gusty, erratic winds are also possible with any
thunderstorm.

Mainly dry conditions overnight with light southerly winds. SCT
convection is expected Monday afternoon and evening.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Air Quality Alert until midnight EDT tonight for KYZ029>031.
IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for
     INZ076>079-083-084-089>092.

&&

$$

UPDATE...EBW
SHORT TERM...KDW
LONG TERM...RAS
AVIATION...EBW