Area Forecast Discussion
Issued by NWS Louisville, KY

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388
FXUS63 KLMK 171031
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
631 AM EDT Wed Jul 17 2019

...Updated Aviation Discussion...

.Short Term...(Today and tonight)
Updated at 226 AM EDT Wed Jul 17 2019

5H trough will continue its slow trek up the Ohio Valley today,
with scattered showers and storms continuing in the warm, moist,
unstable atmosphere. Although precipitable water values may be
slightly lower today than yesterday, heavy downpours can still be
expected. Locally gusty winds will accompany rapidly descending
cores with DCAPEs progged in the 800-1000 J/kg range. Afternoon high
temperatures have outperformed guidance over the past couple of
days, and with a very warm start this morning, have gone on the warm
side today with highs generally in the middle and upper
80s...possibly touching 90 in urban areas. With dew points in the
lower and middle 70s that will result in heat index readings well
into the 90s, briefly touching 100 in a few spots along and west of
I-65.

Tonight the upper trough will continue to push to the east,
resulting in diminishing shower coverage in the middle Ohio Valley.
Winds will become light and variable and with some partial clearing
some patchy light fog may form late in the muggy air. Lows will be
in the lower 70s.

.Long Term...(Thursday through Tuesday)
Updated at 253 AM EDT Wed Jul 17 2019

...Hot And Humid Weather Thursday Into The Weekend...

Upper level ridging will begin to establish itself across the
Tennessee and Lower Ohio Valleys starting Thursday and persisting
through much of the weekend, resulting in a hot, humid, and mostly
dry forecast. The only noteworthy shot of rain may come Thursday as
a weak wave brushes by our CWA and could trigger some showers/storms
during the day. Will err on the drier side of things given the
strength of the upper level ridge building in and subsidence aloft
associated with it for Thursday.

High temperatures Thursday into Sunday will generally range from low
90s near the I-75 corridor to mid/upper 90s west of the I-65
corridor. Factoring in dewpoints, peak heat indices will likely
range from 100-110 degrees, with the highest readings out west.
Given the prolonged duration of heat and that some sites could
briefly reach low-end excessive heat warning criteria, will go ahead
with a Excessive Heat Watch for the entire CWA.

A very substantial, deep trough with an associated surface cold
front is then forecast to dig into the eastern CONUS early next
week, which will result in an abrupt end to the hot, humid, and dry
weather. While the timing of the front varies by model guidance, the
general consensus for fropa is late Sunday into Monday. Expect a
period of stormy weather along and ahead of the front, followed by
cooler, refreshing dry air with Canadian origins behind the front.
Raw surface temperature output from the GFS, ECMWF and Canadian
generally show highs around the low 80s with dewpoints in the 50s
for both Tuesday and Wednesday... something you don`t see too often
near the end of July!

&&

.Aviation...(12Z TAF Issuance)
Updated at 631 AM EDT Wed Jul 17 2019

The upper trough that was once Barry will very slowly work its way
from west to east across the region today and tonight, accompanied
by occasional showers and scattered thunderstorms. Low ceilings will
persist through the morning hours before finally lifting this
afternoon.

Scattered storm development is expected by late afternoon and early
evening in the very warm, moist atmosphere and with the upper trough
still nearby.

Tonight winds will slacken and skies should partially clear over wet
ground and with dew points in the lower and middle 70s. So, some
reduced visibilities in BR will be a possibility after midnight.
Also will need to watch MCS development over the upper Mississippi
Valley but right now it appears that that activity should remain to
our north.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Excessive Heat Watch from Thursday afternoon through Sunday
     evening for INZ076>079-083-084-089>092.

KY...Excessive Heat Watch from Thursday afternoon through Sunday
     evening for KYZ023>043-045>049-053>057-061>067-070>078-081-
     082.

&&

$$

Short Term...13
Long Term...DM
Aviation...13



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