Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 210451

Area Forecast Discussion
National Weather Service Louisville KY
1251 AM EDT THU JUL 21 2016

...Updated Aviation Discussion...

...Forecast Update...
Issued at 900 PM EDT Wed Jul 20 2016

Most of the widely scattered afternoon convection has dissipated,
but still have a cluster of showers dumping heavy rain in Metcalfe
County. Believe this will rain itself out in the next hour, at which
point we can update the legacy forecasts to show a dry forecast for
the remainder of the night.

Still a very juicy environment, so it`s difficult to rule out a
rogue shower or storm somewhere during the night, but any of that
will be too isolated to even warrant a 20 POP. Localized heavy
rainfall that occurred this afternoon, and forecast mins crossing
over afternoon dewpoints, will set the stage for at least localized
fog formation. Will include some patchy fog toward morning,
especially in sections of the south and east that did get rain this

.SHORT TERM (Now through Thursday Night)...
Issued at 300 PM EDT Wed Jul 20 2016

...First Significant Heat of the Summer Coming...

Big story this period will be our going into a heat wave. Already
have had some hot temperatures today, despite a cloud shield over us
from earlier and current convection. Temperatures have reached 90 at
all of the main climate sites. Tomorrow low-level thicknesses
increase, and with more sunshine expected, we should see high
temperatures go more into the low to mid 90s. Dewpoints solidly in
the low to mid 70s along and west of the I-65 corridor, this should
mean heat indices jumping to near 105 in some spots. Debated about
holding off on a heat advisory to Friday, but with the possible
prolonged nature of this event, decided to go ahead with the

A lobe of the ridge aloft should suppress convection tomorrow, so
went ahead and removed noticeable storm chances. Of some concern to
the heat forecast is what the WRF-NMM and ARW both show dropping
down late Thursday night, an MCS. The other models are not showing
such a system, but the flow aloft, being from the north by then
would make sense. Will have to keep an eye on updates to see how
this system evolves in the model domain.

.LONG TERM (Friday through Wednesday)...
Issued at 245 PM EDT Wed Jul 20 2016

...Continued Hot and Humid Likely Through This Weekend...

The WRF`s mentioned above drop that system down quickly Friday
morning. Even if it should develop and come through here, the added
humidity and sunshine later in the day likely will keep heat indices
into the Advisory range, so went ahead and pushed the expiration
time to 00Z Sunday, after coordination with neighboring offices.

That system dropping down should christen us for isolated to widely
scattered storms the next few days...either from systems moving
around the periphery of the ridge or just airmass diurnally driven
thunderstorms. Have storm chances of 20-40 percent through the
weekend, which could provide some cooling relief.

Monday, a frontal boundary will drop into the region. How far south
it gets before stalling is in question. Rain chances should be
highest Monday, with that boundary aiding in storm development and
expansion. After that, rain chances are based on a blended forecast,
and that keeps isolated to widely scattered storms through midweek.
Thicknesses do go down for the work week, but added humidity will
keep heat indices at least in the 90s outside of storms.


.AVIATION (06Z TAF Update)...
Issued at 1252 AM EDT Thu Jul 21 2016

Plan on generally VFR conditions through the TAF period outside of
light fog visibility restrictions possible at BWG early this morning.
Widely scattered storms from yesterday combined with the light winds
and abundant low level moisture overnight could promote fog
development at about anywhere in the region, the greatest likelihood
is across southern Indiana and in the favored south-central KY
locations including BWG.

After mid-morning, plan on light/variable winds with a scattered cu
deck developing by afternoon. Lack of surface convergence and upper
level forcing should preclude storm development today.


.LMK Watches/Warnings/Advisories...
KY...Heat Advisory from noon EDT /11 AM CDT/ today to 8 PM EDT /7 PM
     CDT/ Saturday for KYZ023>030-045-053-061>063-070>075.

IN...Heat Advisory from noon EDT /11 AM CDT/ today to 8 PM EDT /7 PM
     CDT/ Saturday for INZ076>078-083-084-089>092.



Short Term.....RJS
Long Term......RJS
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