Area Forecast Discussion
Issued by NWS Louisville, KY

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817
FXUS63 KLMK 202314
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
714 PM EDT WED JUL 20 2016

...Updated Aviation Discussion...

.SHORT TERM (Now through Sunday)...
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
headline.

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 (Sunday night through Friday)...
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 (00Z TAF Update)...
Issued at 655 PM EDT Wed Jul 20 2016

Main near-term concern is a near-stationary storm just NE of LEX,
and it will be a last-minute call whether we need to initialize with
VCTS. That`s the most likely scenario as long as the storm continues
to sit there, but either way will probably start VFR across the
board with mid-level debris clouds at least.

Storms will die off quickly around sunset with the loss of heating.
Light winds and a juicy atmosphere will set the stage for some fog
potential toward morning. BWG received nearly an inch of rain, so
concern is greatest there, especially given BWG`s climatological
propensity for fog. Confident that temps will cross over afternoon
dewpoints, but not necessarily by enough to result in dense fog.
Will carry several hrs of 3SM, partly to hint at the possibility for
at least brief IFR. Will keep SDF and LEX unrestricted, unless LEX
picks up another shot of heavy rain in the next hr. Conditions
recover to VFR late morning, with light SW winds and only diurnal cu
to worry about in the afternoon.

&&

.LMK Watches/Warnings/Advisories...
KY...Heat Advisory from noon EDT /11 AM CDT/ Thursday 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/ Thursday to 8 PM EDT /7
     PM CDT/ Saturday for INZ076>078-083-084-089>092.

&&

$$

Short Term........RJS
Long Term.........RJS
Aviation..........RAS



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