291
FXUS63 KLMK 191046
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
646 AM EDT Wed Jun 19 2024

.KEY MESSAGES...

*   Seasonably warm and muggy today, then heat builds through the
    weekend with near-record highs Friday and Saturday.

*   Next chance of rain Sunday into early next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 315 AM EDT Wed Jun 19 2024

East Coast ridge continues to strengthen, with the high center
consolidating over New Jersey today. Even though upper heights will
be rising over the Ohio Valley, as the ridge axis takes on a more
east-west orientation, the heat will be limited by an extensive
cirrus shield streaming NNE from the Mississippi Delta. Low-level
thickness progs suggest afternoon highs will run a couple degrees
cooler than Tuesday, with most areas ending up just either side of
90. While that is still above normal, and heat index values will top
out in the mid 90s, it appears to be the best we can do for a
respite from this week`s heat.

The thick cloud cover will also limit instability and keep any
diurnal convection at bay. Confidence in the dry forecast is a bit
limited over southern Indiana, as some of the model progs do spit
out convection and QPF just to the north of our area of
responsibility.

Warm and muggy again tonight as there is minimal change in the air
mass. Min temps close to persistence.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 315 AM EDT Wed Jun 19 2024

Synopsis...Hot and humid conditions will persist during the rest of
the week and extend into this weekend as the strongly anomalous mid-
level high relocates from the Mid Atlantic coast to the southern
half of the CONUS. As a result, pattern aloft will become more
progressive in the top half of the CONUS and feature a series of
northern-stream shortwave troughs which will raise precipitation
chances starting on Sunday and potentially continue at times next
week. Despite the brief heat relief that precipitation can offer,
above-normal temperatures are favored most of the forecast period
under positive mid-level height anomalies and reduced influences
from the tropics.

Model Confidence/Evaluation...Minor adjustments are necessary for
the Thursday - Saturday timeframe given high confidence in the
temperature/heat index forecast, so a persistence approach was
mainly considered with some weight from new guidance. Strength and
location of the anomalous dome of high pressure as well as EFI
guidance keeps hinting at very unusual temperatures for this time of
the year, which might translate to potential record highs Friday and
Saturday (see Climate section below for detailed information). There
is also fairly good confidence in dry weather through Saturday with
decreasing and thinner cloud cover. As mentioned above, showers and
storm chances will return on Sunday ahead of a front, but coverage,
intensity, and even timing are still uncertain pending better model
agreement. Severe weather is not expected at this moment based on
warm temperatures aloft and weak shear.

Thursday - Saturday...Highest temperatures of the medium-range
period will occur in this stretch as the core of positive height
anomalies traverse southward across the Lower Ohio Valley. Best
chances for 100+ afternoon heat indexes are on Friday and Saturday,
especially over urban areas. Although forecast heat index values
will not likely satisfy the advisory criteria, warm overnight
temperatures (in the low 70s) could justify the issuance of headlines
given little to no heat relief for an extended period. Otherwise,
dry weather should prevail as high pressure blocks the northward
moisture transport from the Gulf of Mexico into the Mid Mississippi
while increasing the capping inversion and weakening mid-level lapse
rates.

Sunday - Wednesday...Forecast confidence remains lower for next week
as there is run-to-run model variability regarding the strength and
extension of the mid-level high once it reaches the southern half of
the CONUS and the potential interaction of northern-stream
troughiness with moisture from a tropical surface low over the Gulf
of Mexico. That being said, rain and storm chances will likely
increased on Sunday (ahead of a front) and then by the middle of the
next week (with another frontal wave). Regardless of precipitation
chances, temperatures are favored to remain above-normal (90+) with
a chance of flash drought development over southern Indiana given 30-
day precipitation deficits of 1-3 inches, below-average soil
moisture, persisting high temperatures, and high evapotranspiration
demand.

&&

.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/...
Issued at 645 AM EDT Wed Jun 19 2024

Mid-level cig has taken over HNB and is in the process of spreading
into SDF and BWG as a tropical plume aloft streams NNE across the
Ohio Valley. Not expecting any disruption to VFR conditions, and it
should simply give way to a cirrus ceiling by mid/late morning.
Light winds with a general southerly component, initially S-SE less
than 5 kt, veering to S-SW with mixing but staying under 10 kt. By
around sunset winds will go near-calm again, and ceilings will
scatter out as we lose the tropical plume.

&&

.CLIMATE...
Issued at 315 AM EDT Wed Jun 19 2024

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


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

Louisville:       98/98     (1988)

Bowling Green:    96/102    (1933)

Lexington:        97/97     (1988)


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

Louisville:       98/100    (2022)

Bowling Green:    97/102    (1901)

Lexington:        97/99     (1988)


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

Louisville:       95/98     (1988)

Bowling Green:    96/104    (1930)

Lexington:        93/96     (1988)


Note 1: Sunday temperatures are highly dependent on the arrival
of an approaching cool front. If the front ends up slower, as
some data suggests, then forecast temperatures will trend
warmer.

Note 2: 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 from midnight tonight to midnight EDT
     Thursday night for KYZ029>031.
IN...Air Quality Alert from midnight EDT /11 PM CDT/ tonight to
     midnight EDT /11 PM CDT/ Thursday night for INZ076>079-
     083-084-089>092.

&&

$$

SHORT TERM...RAS
LONG TERM...ALL
AVIATION...RAS
CLIMATE...RAS