Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 191544
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1144 AM EDT Wed Jul 19 2017

.Forecast Update...
Issued at 1140 AM EDT Wed Jul 19 2017

The Air Quality Alert for the Louisville Metro Area was extended
into Thursday by the Louisville Metro Air Pollution Control District
and the Indiana Department of Environmental Management.  Air quality
is forecast to be at the Orange level for today and Thursday which
may result in some health effects for sensitive groups.

Issued at 1020 AM EDT Wed Jul 19 2017

Updated the forecast to include a 20% chance of a shower or sprinkle
today mainly west of I-65 as an upper level shortwave passes
through.  This wave is currently producing some light isld
convection over IL/IN and high-res models do indicate that a few
cells may pop up in our area late this morning or this afternoon.
High temperatures still look to reach the upper 80s/lower 90s today
with heat indices ranging through the 90s.

&&

.Short Term (Now through Thursday)...
Issued at 255 AM EDT Wed Jul 19 2017

Weak gradients at night make the residual surface boundary quite
difficult to pick out, but pressure pattern suggests it is somewhere
over central Kentucky. However, moisture pooling is actually fairly
limited and we are even seeing mid-60s dewpoints across most of
southern Indiana, and even nosing across north central Kentucky,
well into the Bluegrass region.

Precip yesterday was very isolated, and with the upper ridge
continuing to build, would expect very little if anything in the way
of convection today. Even more confidence in a dry forecast on
Thursday.

Biggest story through Thursday, and even into the weekend, will be
the heat and humidity. ECMWF is quite bullish on temps, but our
forecast leans much more heavily on GFS/NAM consensus given recent
performance and continued greenness as a limiting factor on temps.
Highs today will reach the lower 90s, with heat index values barely
cracking 100, if they even get there at all. Incrementally warmer on
Thursday with more mid-90s likely to go on the board, but warmest
heat index values appear to be 100-103 west of Interstate 65. This
is solidly below the threshold for any headlines. Even though it`s
still another day out, the duration of the upcoming heat supports a
Special Weather Statement a bit farther ahead of time.

.Long Term (Thursday night through Tuesday)...
Issued at 255 AM EDT Wed Jul 19 2017

Friday will be the hottest day of the upcoming week under the
strongest upper ridging. Still not buying the upper 90s advertised
by the Euro as we are just too green. Friday will be the best shot
at actually meeting Heat Advisory criteria, with temps in the
mid 90s and heat indices pushing 105 degrees west of Interstate 65.

Upper ridge starts to flatten out on Saturday, taking some of the
edge off of the heat, but heat indices will still top out around
100. The greater sensible wx impacts will be a bit more cloud cover
and the return of isolated convection, especially near the
Interstate 75 corridor.

Transitional days on Sunday and Monday as a fairly sharp upper trof
pushes across the northern Great Lakes and into eastern Canada,
driving a slow-moving cold front into the Ohio Valley. Precip
chances peak on Sunday, but we will still cap POPs at 50% each
afternoon, with the best chances from Lake Cumberland northward into
the Bluegrass.

Modified Canadian surface high builds in Tuesday to provide at least
a couple days` respite from both the 90 degree temps and the high
dewpoints. Temp forecast actually trends a couple degrees below
climo day and night heading into the middle of next week.

&&

.Aviation...(12Z TAF Issuance)
Issued at 625 AM EDT Wed Jul 19 2017

The only aviation issue today is patchy, light fog this morning. BWG
and LEX both have vsbys around 6SM, and BWG in particular could
briefly drop to MVFR between now and 12z. Otherwise, the rest of the
day will feature prevailing VFR and light winds.

A weakening mid-level wave of low pressure will bring some scattered
clouds above 10 kft this afternoon. A northwest breeze around 5-6
kts will develop by 15z, with winds going light once again toward
sunset.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Update...AMS
Short Term........RAS
Long Term.........RAS
Aviation...EBW


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