Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 231857

Area Forecast Discussion
National Weather Service Louisville KY
257 PM EDT Sun Jul 23 2017

.Short Term...(This evening through Monday night)
Issued at 235 PM EDT Sun Jul 23 2017

Surface analysis and visible satellite imagery reveal a weak surface
trough draped across portions of southern Indiana. Winds behind the
surface trough were generally out of the west, while winds ahead of
the trough were out of the south. Visible satellite reveals some
cumulus starting to develop along portions of the surface trough,
and we should see the cu field become more widespread over the next
couple of hours as atmosphere begins to destabilize in the wake of
the departing MCS. High-res models indicate showers and
thunderstorms eventually developing along and ahead of this surface
trough as it pushes eastward later this afternoon. If enough
destabilization can occur, there could be a couple of isolated
strong to marginally severe storms. Main threats with the stronger
storms would be gusty winds.

Regarding the heat advisory currently out, heat indexes within the
advisory at this hour are generally in the low to mid 90s. The
convection and outflow from this morning certainly limited how warm
it was going to be today, but think there is still the potential for
areas within the advisory to reach heat index values within 100-105
degrees, so will keep it going until 00z.

Activity will die down early this evening, with the last of the
showers and storms hanging around the Lake Cumberland region. Fog
could develop this evening into tomorrow morning, especially in
areas where heavy rain fell or will fall today. Could see some areas
of dense fog as well, but not enough to warrant an advisory at this

Any fog should burn off shortly after sunrise Monday. A weak "cold"
front will move in from the north during the day Monday, and could
spark off some isolated to scattered showers and thunderstorms.
Majority of precipitation should be diurnally driven, with the
greatest coverage of showers/storms during peak heating. Weak deep
layer shear and modest instability could lead to some isolated
strong to severe storms tomorrow afternoon. Flash flooding doesn`t
look to be much of a threat due to lack of spatial coverage of
storms and minimal storm training. Storm activity should die down
toward sunset, and give way to a mostly clear and calm evening.


.Long Term...(Tuesday through Sunday)
Issued at 240 PM EDT Sun Jul 23 2017

By Tuesday, surface high pressure will be over the Great Lakes
region and advecting in slightly cooler and drier air from the
north. Over time, the surface high will drift eastward and weak
upper level ridging will build in and slowly increase
temperatures/moisture through the mid-week period.

By the Thursday/Friday timeframe, a strong shortwave and associated
cold front will move through the lower Ohio Valley. Widespread
showers and storms will develop along and ahead of the front, but
looks like most precipitation should taper down Friday evening. The
weather over the weekend is looking absolutely wonderful by end of
July standards, with mostly sunny skies, highs generally in the low
to mid 80s, dewpoints in the low to mid 60s, and light refreshing
northerly winds.


.Aviation...(18Z TAF Issuance)
Issued at 105 PM EDT Sun Jul 23 2017

The challenge for the TAF forecast this afternoon will be
convection. Models have not been handling the morning precipitation
very well, so confidence in the forecast this afternoon is lower
than normal. Showers have begun to once again develop and will
affect SDF soon. SDF is the least likely to see thunderstorms this
afternoon thanks to the morning rain, so have taken TS out of the
TAF there. Storms will be possible at LEX and BWG with the better
chance for BWG. Therefore will mention TS at these sites for a few
hours this afternoon.

For tonight we should see some clearing across the region with winds
becoming light. Some light fog is expected to develop. For tomorrow,
VFR conditions are expected after the fog mixes out with winds out
of a more westerly direction.


KY...Heat Advisory until 7 PM CDT this evening for KYZ026-061-062-



Short Term...DM
Long Term...DM
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