753
FXUS63 KLMK 201535
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1135 AM EDT Thu Jun 20 2024

.KEY MESSAGES...

*   Patchy light fog at sunrise. Well above-normal temperatures
    today with peak heat index values in the upper 90s.

*   Heat continues for the end of the week into the weekend with
    near-record highs for some locations Friday into Sunday.

*   Scattered showers and storms possible Sunday, and again by
    midweek of next week.

&&

.UPDATE...
Issued at 1134 AM EDT Thu Jun 20 2024

Visible satellite imagery is showing the development of a Cu field
across parts of southern IN/central KY. Expect to see this continue
into the afternoon. Model soundings show good subsidence above 800mb
along with slight temperature inversion between 700-800mb this
afternoon. Mixing this afternoon could help lower dew points from
the low 70s into the upper 60s thanks to mixing but with afternoon
temperatures still expected to be in the low/mid 90s heat index
values are expected to be in the mid/upper 90s with a few isolated
locations feeling like it is 100. The overall forecast remains on
track, the only change was to tweak cloud/sky coverage this
afternoon.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 315 AM EDT Thu Jun 20 2024

Synopsis...Center of anomalous mid-level high and surface
reflection will settle over the region during the next 24 to 48
hours, reinforcing dry and hot conditions over the Lower Ohio
Valley. In addition, a fairly humid airmass will combine with the
warming temperatures to yield heat indexes in the upper 90s.

This Morning...Current nighttime satellite RGB reveals the expected
dissipation of upper clouds with a good signal from the developing
fog across eastern Kentucky. For central Kentucky, surface
observations indicate saturated conditions across most of the area,
but only a few sites along and east of I-75 are reflecting reduced
visibilities. Judging by the low-level winds in the latest LEX ACARS
and oscillations in some of the RH inversion profiles of the KY
Mesonet, there might be sufficient BL mixing to inhibit greater fog
coverage. On the other hand, more protected zones and/or river
valleys across the Bluegrass and Cumberland areas are already
experiencing reduced visibilities and that will be the trend until a
few hours after sunrise.

Afternoon/Evening...Main story today continues to be the
increasingly hot temperatures and peak heat index values between 95
to 100 degF. The position and strength of the high pressure system
will foment light and variable winds with strong capping inversion
in the 800-700 mb layer. As a result, the shallow diurnal cumulus
field should not exhibit any significant convective development to
produce precipitation. That being said, some members of the HREF
guidance are hinting at isolated afternoon showers across south-
central KY where a tongue of PW/instability will exist. Although a
brief light shower would not be impossible, it is certainly very
conditional and regarded low confidence to mention in this update.

Tonight...Loss of daytime heating will allow skies to be mostly
clear after sunset with BL winds becoming calm or light and
variable. Therefore, will include at least a mention of patchy light
fog after midnight with HREF visibility output suggesting a better
chance of a widespread episode for the eastern half of the area.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 315 AM EDT Thu Jun 20 2024

Our stubborn, anonymously large upper level ridge will nearly be
centered over the region Friday morning but will begin to gradually
retrograde westward going into the weekend. Hot and humid conditions
will be likely in this pattern, with afternoon highs Friday into
Sunday climbing into the mid/upper 90s, and peak heat indices
ranging from 96-102 degrees. Air temperatures at a few locations may
flirt with record highs... see the climo portion of the AFD for more
details.

Models continue to indicate that our region will receive a glancing
blow from an upper level trough on Sunday. At the surface, a weak
frontal boundary could serve as a lifting mechanism for convection,
though models aren`t too overly excited with the prospect of
widespread precipitation given the better forcing/dynamics will be
off to our north. Deep layer shear is weak (0-6km bulk shear less
than 25kts), but modest instability values and high DCAPE (>1,000
J/KG) will support gusty downbursts in stronger storms.

After a brief `cool-down` on Monday (highs in the upper 80s, low
90s), temperatures may begin to steadily increase again going into
midweek. Much of this will depend on the deepening and westward
extent of troughing in the eastern CONUS. The first part of next
week will likely feature dry conditions, but we may start to see
shower/storm chances slightly increase by midweek as low level
moisture increases.

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 654 AM EDT Thu Jun 20 2024

Discussion...Surface high pressure settling over the Lower Ohio
Valley will support VFR conditions and light, variable winds today.
This morning fog episode has been intermittently dense (IFR or lower)
at HNB and more recently BWG. Current thinking is for visibilities
to improve by 12Z with a persistent cloud deck slowly ejecting to
the north. Calm winds and mostly clear skies could promote another
fog event tonight, an scenario that HREF has been suggesting for a
couple of runs now.

&&

.CLIMATE...
Issued at 315 AM EDT Thu Jun 20 2024

================== Near-Record Heat This Weekend ==================


               Friday 6/21/2024
          Max T Fcst/Record (Year)

Louisville:       97/98     (1988)

Bowling Green:    96/102    (1933)

Lexington:        96/97     (1988)


             Saturday 6/22/2024
          Max T Fcst/Record (Year)

Louisville:       97/100    (2022)

Bowling Green:    97/102    (1901)

Lexington:        96/99     (1988)


               Sunday 6/23/2024
          Max T Fcst/Record (Year)

Louisville:       95/98     (1988)

Bowling Green:    97/104    (1930)

Lexington:        93/96     (1988)


Some records may have occurred in multiple years. The latest year
the record was tied is displayed.

&&

.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...BTN
SHORT TERM...ALL
LONG TERM...DM
AVIATION...ALL
CLIMATE...DM