Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 171905
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
305 PM EDT Thu Aug 17 2017

.Short Term...(This evening through Friday night)
Issued at 300 PM EDT Thu Aug 17 2017

Current satellite and radar imagery shows mostly sunny skies across
much of central Kentucky with partly cloudy skies across far west KY
and southern Indiana.  A progressive line of showers and
thunderstorms continues to move eastward across far southern IN and
far northern KY.  This activity looks to stay mainly north of the
Bluegrass Parkway this afternoon.  Currently, temperatures are in
the upper 80s to around 90 in most locations.  Some of the warmer
urban areas may high 94-95 in the next hour or two.

The atmosphere will remain moderately unstable through the afternoon
along with plentiful moisture in place across the region.  The best
shear however, will remain generally north of KY across central IN
into Ohio.  Additional thunderstorms are expected to develop within
the next hour or two over western Kentucky.  These storms will move
eastward into far southern IN and much of central Kentucky later
this afternoon and into the evening hours.  A moderately unstable
airmass will remain in place so thunderstorms could be rather
strong, with a few of them possibly exceeding severe limits.  The
main hazards will be torrential rainfall, gusty winds, and frequent
lightning. Some localized flooding will also be possible, in areas
of poor drainage and in areas that see repeated storm activity.

The storms are expected to end from west to east this evening, with
the best chances of rainfall late this evening into the overnight
period in areas east of the I-65 corridor.  Lows tonight will only
drop into the lower 70s east of I-65, but some cooler air may reach
our far NW counties where some upper 60s will be possible.

High pressure will then quickly build in for the day on Friday with
mainly dry weather and dewpoints about 8-10 degrees lower than
today. Some patchy morning fog will be possible in the low-lying
areas.  Afternoon highs will warm into the 84-88 degree range.  Dry
conditions are expected into Friday night with lows in the middle
60s.

&&

.Long Term...(Saturday through Thursday)
Issued at 305 PM EDT Thu Aug 17 2017

Saturday through Sunday Night...

A quick moving upper trough axis is forecast to move through the
southern Great Lakes and northern Ohio Valley on Saturday.  Moisture
return ahead of this system will be very limited.  However, there
could be just enough moisture to squeeze out a few showers and
storms over southern IN and far northern KY during the afternoon
hours.  The trough axis is then expected to shift eastward with
upper level ridging building into the area.  This will result in
mainly dry conditions for Saturday night through Sunday night.

Highs Saturday and Sunday will average in the upper 80s to around 90
with overnight lows in the middle to upper 60s.

Eclipse Day...

Overall, there are no real significant changes for the forecast on
Monday.  High pressure at the surface and aloft is expected to
remain in place across the region.  Kentucky looks to remain on the
northern periphery of the ridge and some of the model data still
suggests that some isolated afternoon/eve storms could pop up. Skies
look to remain mainly clear in the morning with a diurnal cumulus
field developing by late morning into the afternoon hours.  In
general terms, very typical for late August in the Ohio Valley.

The larger weather story emerging here will be the expected warmth
and increasing humidity. Temperatures Monday afternoon will likely
top out in the upper 80s to the lower 90s.  Those temperatures
combined with dewpoints in the upper 60s to near 70 will produce
heat indices in the 95-100 degree range. Locally higher values may
be attainable in spots such as green fields and near corn fields
where evapotranspiration will be locally maximized.

Tuesday-Thursday...

A return to a more active period of weather looks to take place as
we move into the Tuesday-Thursday time frame.  The models are
forecasting a digging upper trough to push in from the northwest
with an associated surface cold front.  This should bring another
round of showers and thunderstorms to the region from Tuesday
afternoon through Wednesday afternoon.  The front will stretch out
and slow down as it moves through the region.  However, it does
appear that a more significant push may shove it further south into
the Tennessee Valley by Thursday.  For now, have trended PoPs higher
in the Tues/Wednesday time frame...with drier conditions for
Thursday.  Temperatures look to warm into the upper 80s on Tue/Wed
with highs retreating to the upper 70s to the lower 80s by Thursday.

&&

.Aviation...(18Z TAF Issuance)
Issued at 126 PM EDT Thu Aug 17 2017

Showers and thunderstorms have begun to develop ahead of an
approaching cold front. These storms may affect the TAF sites this
afternoon into the evening hours. These storms will produce heavy
rainfall that will reduce visibilities if they directly affect the
airfield, so have included TEMPO groups at each site during the most
likely window for storms. These storms should move east of the
region by 00-02Z. However, a few showers may linger around LEX
through 06Z or so.

Winds whit afternoon will be gusty out of the southwest. The gusts
should subside this evening and winds will shift to more westerly
behind the front overnight. Some low stratus looks to develop at LEX
tonight with MVFR to possibly IFR cigs developing. BWG is more
questionable with the ceilings as clouds may start to break up there
earlier with the front passing through, so have kept clouds
scattered early tomorrow morning.

&&

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

$$

Short Term...MJ
Long Term....MJ
Aviation.....EER



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