Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 210132
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
932 PM EDT Sun Aug 20 2017

.Forecast Update...
Issued at 932 PM EDT Sun Aug 20 2017

The forecast is largely on track tonight. Only concern is for some
patchy fog development, given decent radiational cooling and high
low level moisture. One factor hurting confidence a bit will be the
possibility of upper sky cover from upstream convective complexes
limiting outgoing radiation. Think most areas should remain mostly
clear overnight, so will go with patchy fog wording. Best chance for
a few pockets of dense fog would be in river valleys.

Otherwise, things look on track through the overnight with all eyes
on the eclipse for tomorrow. No changes in that department at this
time.

&&

.Short Term...(This evening through Monday night)
Issued at 245 PM EDT Sun Aug 20 2017

...High clouds filtering in on Monday...

Well, all eyes are on tomorrow`s highly anticipated solar eclipse.
The forecast remains hot and dry. However, confidence in the cloud
cover forecast is still only medium. This morning`s MCS has weakened
to a band of showers along the Mississippi River in far eastern
IA/western IL. The system`s outflow has pushed into central IL,
extending SW into southeast MO. Convection across southern MO is
likely to diminish this evening with the loss of heating.

Shortwave over eastern IA this afternoon is forecast to swing east
this evening and overnight, and convective redevelopment appears
likely from northern IL into northern IN. Multiple hi-res models
support this idea. Meanwhile, larger scale MCS development is
expected once again across Iowa on the nose of stronger LLJ/warm
advection. Thus, cirrus shield will likely slowly spill southeast
into Monday morning. A thicker cirrus canopy is more likely across
southern IN/northern KY, while the path of totality should just see
scattered thin cirrus. A widely scattered cu field is also expected
to develop around 6 kft after 16z. One of these clouds could drift
by, briefly obscuring a view of the eclipse for some.

Highs Monday afternoon, outside of the eclipse, will reach the lower
90s. Afternoon Heat Index values will peak in the 95-100 degree
range, mainly in the hours immediately after the eclipse. Those
planning to spend an extended period of time outdoors should dress
for the weather and stay hydrated. A Special Weather Statement will
continue for the hot and humid conditions. Lows Monday night will
only drop into the low/mid 70s ahead of an approaching cold front.
Mainly dry weather is expected Monday night, though precip chances
ramp up quickly Tuesday morning.

.Long Term...(Tuesday through Sunday)
Issued at 247 PM EDT Sun Aug 20 2017

Tuesday - Wednesday...

A strong cold front will approach the area Tuesday and slowly move
through Tues night into Wed. The front will likely bring a line of
strong to severe storms Tues afternoon/evening.  Forecast soundings
indicate MLCAPE could increase to around 2000 J/kg, with 0-6 km bulk
shear values of 25-35 kts. Damaging winds are the primary threat.
Heavy rainfall will also be possible Tuesday through Wednesday
morning. The front`s southward progress does slow by Wednesday, so
thunderstorms may linger south of the WK/BG parkways.

As for temps, Tuesday looks to be the last hot and humid day.  Highs
will range from the mid 80s to low 90s across the region with heat
indices maxing out in the mid to upper 90s before convection
arrives. Temps will remain mild Tues night with lows ranging through
the 60s to around 70. Wednesday highs will be much cooler in the
upper 70s/lower 80s.

Thursday - Saturday...

A broad trough will settle over the Midwest through Fri providing
cooler, pleasant weather.  Expect dry conditions with highs in the
upper 70s/lower 80s and lows in the 50s!  Saturday temps may begin
to warm a little more as the trough moves east of the region.

&&

.Aviation...(00Z TAF Issuance)
Issued at 741 PM EDT Sun Aug 20 2017

VFR is expected to prevail at the TAF sites this forecast cycle,
with the exception of some MVFR fog at BWG toward dawn. A look at
afternoon crossover T`s suggest we don`t crossover, but may be close
enough to warrant some MVFR vis. This matches up with some of the
latest guidance as well.

Otherwise, expect light and variable or calm winds overnight with
mostly clear skies. Expect a few-sct cu around 5-6 k feet, with some
upper sky cover by afternoon as well. Winds will pick up out of the
southwest between 5 and 10 mph.


&&

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

$$

Update...BJS
Short Term...EBW
Long Term...EBW
Aviation...BJS



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