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329
FXUS63 KLMK 181917
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
317 PM EDT Tue Jun 18 2024

.KEY MESSAGES...

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*   Above normal temperatures expected on Wednesday with
    increasingly warm conditions for the late week and into the
    weekend.

*   Spotty coverage of afternoon thunderstorms this afternoon and
    evening, then dry Wednesday through Saturday.
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&&

.SHORT TERM /THROUGH WEDNESDAY/...
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Issued at 317 PM EDT Tue Jun 18 2024

Afternoon obs show a mix of sun and clouds across the region.  The
clouds have kept temps down a bit this afternoon with highs so far
today in the upper 80s to the lower 90s.  Dewpoints were in the
upper 60s to the low 70s resulting in heat indices in the upper 90s
to the very low 100s in a few spots.  Radar showed a few areas of
convection across the region this afternoon.  Our area is on the
southwest flank of an upper level high which is centered off to our
northeast.

A ring of convection has fired this afternoon from northern TN
northwest into southwest KY and southwest IN.  Mesoscale analysis
shows stronger instability over eastern KY with a gradient of SBCAPE
across central and into western KY.  In general, SBCAPE decreases a
bit as one heads east of I-65.  West of I-65 SBCAPE was in the 1500-
2000 J/kg range with 2000-2500 J/kg of CAPE out east of I-75.  Bulk
shear was rather weak across the area which will likely limit
overall convective growth.  Plenty of DCAPE was available however
and storms this afternoon/evening will be of the pulse variety.
Damaging downburst winds, intense CG lightning, and heavy rainfall
will be the main threats with this activity.  The most concentrated
area of convection this afternoon should be from northern TN into
the Bowling Green area and then northwestward toward
Evansville/Owensboro.  More isolated-scattered convection will be
likely across the remainder of the forecast area through sunset and
then convection should quickly diminish as the PBL cools.  Highs on
the day will be in the upper 80s to the lower 90s and should occur
in the next 60-90 min.  Temps will slowly cool this evening, except
in areas that get a thunderstorm where a 15-20 degree cool down would
be possible.  Rainfall amounts with these storms could be impressive
with a quick quarter to three quarters of an inch being possible.
Locally higher amounts could occur if storms were to train over a
location.

For the overnight period, generally quiet weather is expected,
though I can`t rule out an isolated shower/storm, mainly over our
southern IN counties.  Overnight lows will be in the upper 60s to the
lower 70s in most spots.  The urban heat islands will remain in the
mid-upper 70s overnight.

For Wednesday, upper level ridge will remain centered to our east,
but the models show a bit of expansion of the ridge to the west as
heights slowly rise across the region.  Model soundings show some
warming in the 850-700 hPa layer which will likely result in a bit
more capping across the region.  CAMs are much drier here and this
agrees well with previous forecasts showing a drier trend beginning
around this period.  Given that model soundings show a bit of
saturation in the 300-200 hPa layer, we`ll probably have a bit of
high cloud cover once again which will keep temperatures down.  Have
gone closer to the CONSShort guidance here with highs in the upper
80s to the lower 90s.
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&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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Issued at 317 PM EDT Tue Jun 18 2024

Anomalous (+2-3 SD height anomalies) mid/upper level ridging is
forecast to retrograde westward across the Mid-South Thu and Fri. In
fact, the center of the 500 mb high is forecast to pass directly
over the Lower OH Valley during this time frame, providing plenty of
subsidence and continued hot, dry weather.

Wednesday night looks partly cloudy and mild with lows in the upper
60s to lower 70s. Thursday will be another hot day with afternoon
highs in the low to mid 90s. Sfc dewpoints/humidity are still
forecast to be just a touch lower, which will help "limit" heat
indices to the mid/upper 90s.

The heat will reach its peak Friday and Saturday. 1000-850 mb
thicknesses and temps tick upward a little bit each day.
Temperatures are expected to max out in the mid/upper 90s, and a
couple sites will approach 100 degrees. A couple daily record highs
could be in jeopardy, particularly the record highs for June 21 at
SDF and LEX (see Climate section for more details. Heat index values
around 100 will be possible both days.

By late in the weekend, it will still be hot. But ridging aloft is
oriented more west-east by this time and suppressed across the
southern US. This occurs as a stronger wave of low pressure moves
east across the northern US. As this system tracks across the Great
Lakes, it will drag a weak cold front through the region late Sunday
into Monday. This will bring a chance for showers and thunderstorms
back to the region, though rain chances are only around 30% at this
time. Temperatures still appear likely to warm well into the 90s on
Sunday prior to the arrival of the front and associated cloud cover.
After a hot, dry stretch, any rainfall with this front will be
welcome. Confidence remains low on rainfall amounts at this time.
The concern for rapid onset drought conditions will certainly by
higher by this weekend, especially if rainfall amounts are light
late Sun into Mon.

Some good news: model guidance suggests the possibility of more
persistent upper level troughing during the middle of next week.
There is a stronger signal for appreciable rainfall in the 6-10 day
time frame.
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&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
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Issued at 317 PM EDT Tue Jun 18 2024

Expecting mostly VFR at the TAF sites through this afternoon and
evening, with the caveat that a brief t-storm chance will exist
mainly at BWG/HNB. Like the going mention of thunder potential at
those sites, with chances farther east lesser due to low coverage
and a less favorable environment. Therefore, will keep mention out
at SDF/LEX/RGA.

Outside of the storm chances, expecting a fairly quiet period with
steady SSW winds this afternoon shifting to a lighter SE component
overnight. Cloud cover will feature diurnally driven cumulus with
some variable mid and upper cloudiness as well.
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&&

.CLIMATE...
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Issued at 317M EDT Tue Jun 18 2024

================== Near-Record High Temps ==================

             Thursday 6/20/2024
          Max T Fcst/Record (Year)

Louisville:       96/100     (1953)

Bowling Green:    94/102     (1936)

Lexington:        95/100     (1953)



               Friday 6/21/2024
          Warm Min T Fcst/Record (Year)

Louisville:            98/98     (1988)

Bowling Green:         97/102    (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
               Warm Min T/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 1: Some records may have duplicate years. The latest year
the record occurred is displayed.
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&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Air Quality Alert from midnight Wednesday night to midnight
     EDT Thursday night for KYZ029>031.
IN...Air Quality Alert from midnight EDT /11 PM CDT/ Wednesday
     night to midnight EDT /11 PM CDT/ Thursday night for
     INZ076>079-083-084-089>092.

&&

$$

SHORT TERM...MJ
LONG TERM....EBW
AVIATION.....BJS
CLIMATE......EBW