Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 212342
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
742 PM EDT Mon Aug 21 2017

...Updated Aviation Discussion...

...Forecast Update...
Issued at 508 PM EDT Sun Aug 20 2017

Thunderstorms over the lower Wabash River Valley, have gusted out
per the latest VWX radar scans. The very visible outflow boundary is
now a good 5 to 10 miles ahead of the storms and pushing southward.
For this reason, will continue to keep our southern Indiana counties
dry as observations match up with latest hi res data that
convection won`t make it into Dubois county. One thing we will have
to watch is the outflow boundary as it travels southward along a
very tight and strong instability axis. The enhanced low level
convergence along this feature could spark additional t-storms, most
of which should stay just west of our western CWA counties. Will
continue to monitor through the early evening.

.Short Term (Now through Tuesday Night)...
Issued at 340 PM EDT Mon Aug 21 2017

Well the eclipse has come and gone, and the clouds cooperated across
central KY and southern IN. The shade and cooling from the eclipse
did indeed wipe out the cumulus field, so skies remain mostly sunny
this afternoon. Temperatures dropped anywhere from 4-10 degrees
during the eclipse! Temps are starting to recover, however, and will
top out in the low 90s this afternoon. Heat indices will peak in the
mid/upper 90s through about 6 pm local time.

A line of convection oriented NE to SW has formed across central
IN/IL along an outflow boundary. This activity will progress
southeast toward our southern Indiana counties this evening,
weakening as it moves into a drier, less unstable environment.
Convection will also diminish with the loss of heating, but can`t
rule out showers or a rumble of thunder to the north of I-64 around
22-00z. Dry conditions are expected tonight with skies ranging from
mostly clear to partly cloudy. Lows will be in the low/mid 70s.

Rain chances ramp up across southern IN/northern KY Tuesday morning
ahead of a strong cold front. A very warm, humid airmass will be in
place ahead of this boundary. Numerous showers and thunderstorms can
be expected Tuesday afternoon through Tuesday night. Deep layer
shear around 30 kts (primarily unidirectional) supports multiple
bands of convection with a risk for damaging winds and heavy rain.
SPC`s Day 2 Slight Risk makes sense and highlights the threat well.
Highs on Tuesday are tricky and will depend on convective
development. But high temps should generally range from the mid 80s
in southern IN to around 90 in southern KY.

.Long Term (Wednesday through Monday)...
Issued at 350 PM EDT Mon Aug 21 2017

Shower and thunderstorm activity is likely to persist south of the
WK/BG parkways Wednesday morning as the cold front gradually clears
the area. Much cooler, less humid air streams in behind the front,
with Wednesday highs only around 80 degrees.

The rest of the week will feature spectacular weather, and you`ll be
thinking of Fall. Canadian high pressure builds down into the Great
Lakes as the upper trough swings through. Fair weather is expected
through the end of the work week. Humidity levels will be low, with
highs in the upper 70s/low 80s and overnight lows in the 50s to
around 60. Rain chances will increase Sunday but especially into
early next week as a low pressure system advances toward the Ohio
Valley.

&&

.Aviation (00Z TAF Update)...
Issued at 742 PM EDT Mon Aug 21 2017

Thunderstorm activity to our northwest should remain just northwest
of the terminals, though widespread cirrus will spill into the skies
over southern Indiana and central Kentucky.

On Tuesday a cold front will approach from the northwest and cross
the Ohio River Tuesday evening. Showers and thunderstorms will be
widespread ahead of the front from late morning into early evening.
Some severe storms will be possible, especially during the afternoon
and evening hours.

&&

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

$$

Update.........BJS
Short Term.....EBW
Long Term......EBW
Aviation.......13



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