Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 231704
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
104 PM EDT SAT JUL 23 2016

...Updated Aviation Discussion...

...Forecast Update...
Issued at 1000 AM EDT Sat Jul 23 2016

Seeing a few quick hitting showers in the Hopkinsville area this
morning, where the airmass is most moist.  Otherwise just have some
passing cirrus. These, along with boundaries left over from
yesterday`s rains, may be enough to spark off some additional
isolated to scattered storms in the mid to late afternoon hours.
Best chance looks to be along and south of a Hartford to Georgetown
line in Kentucky. Cannot rule out isolated storms north of the line.
High temperatures look to peak in the lower 90s. Heat indices in the
advisory area should range from 100-105. Will wait until mid
afternoon to make a decision on either extending the heat advisory
or dropping it altogether.

.SHORT TERM (Now through Sunday)...
Issued at 300 AM EDT Sat Jul 23 2016

...Hot and Humid Conditions Continue with Scattered Storms in the
Afternoon...

In the near term, mostly clear skies were noted across southern
Indiana and portions of far northern Kentucky.  Partly to mostly
cloudy conditions were seen across southern KY where leftover
convective debris was located.  Some drops in visibility have been
reported in the areas where skies cleared out...mainly across
southern IN and southern IL and some pockets in Kentucky.  Latest
high resolution guidance continues to show best fog chances across
southern IN and northern KY this morning while convective debris
down across the south will likely keep fog in check.  Temps were
mild with readings generally in the lower to middle 70s.

Over the next few hours, we expect the fog to expand a little
more...mainly in the north.  Current thinking is that it will not
likely develop enough to warrant an advisory, but will continue to
monitor.  Some additional light showers will be possible across
southern parts of the region through sunrise.  Lows will likely drop
about another degree to their overnight minimums before rising after
sunrise.

For Today, another hot and very humid day is on tap.  With less
expected cloud cover at the start of the day, it looks like we`ll
heat up a bit faster than we did on Friday.  Plenty of moisture will
be available and instability will increase through the afternoon. We
do have some left over boundaries from yesterday`s convection out
there and those will likely serve as a trigger for afternoon
convection.  Looking at the ensemble and deterministic CAMs, this
afternoon`s coverage looks isolated to scattered...with most of it
contained across Kentucky.  Given what`s happened over the last few
afternoons, have kept scattered convection in the forecast for the
afternoon.

As for temperatures, the models have performed very poorly over the
last few days.  They have not handled convection, convective cloud
debris, or our exceptionally green vegetation coverage all that
well.  The blended model guidance which contains observed grids in
their calculations have finally caught on to the pattern.  Highs
today will likely warm into the lower 90s once again.  These temps
combined with dewpoints in the low-mid 70s will result in heat
indices near heat advisory generally west of the I-65 corridor with
lower heat indices over in the Bluegrass region.  For now, the
current heat advisory looks good in its placement and will leave
intact.

For Tonight and Sunday, late afternoon/eve convection will likely
taper off quickly after sunset with some partial clearing overnight.
Some patchy fog will be possible in the typical fog prone areas and
lows will drop back into the low-mid 70s.  Scattered thunderstorms
will develop once again in the afternoon and isolated-scattered
coverage looks likely once again.  The blended guidance has come
down a little bit on highs with readings generally in the lower 90s.
This looks to keep heat indices below criteria and we have no plans
to place the area under another heat advisory at this time.

.LONG TERM (Sunday night through Friday)...
Issued at 300 AM EDT Sat Jul 23 2016

...Upper Pattern To Break Down With Heat/Humidity Abating and
Storminess Increasing Significantly...

The latest long term model guidance continues to show the breakdown
of the upper level ridge and a return of a more amplified flow over
the eastern half of the US.  This is really not a surprise as this
type of pattern transition has been a recurring theme over the last
8-10 weeks.

Early in the week, we`ll see the first in a series of upper troughs
move through the region.  This will shunt the periphery of the ridge
to our south and west.  As this feature passes through, we`ll see a
weak front push through the region brining an uptick in rain chances
to the region.  With the flow flattening back out by Tuesday, this
boundary will loose its southward push and likely stall out across
the region.  This boundary will likely serve as an effective
boundary for multiple rounds of convection to move along as a series
of mid-level perturbations move through the region.  As in the past
several weeks, it has been difficult to time these perturbations
moving through the region at these longer ranges.  In any case, a
rather unsettled weather pattern looks likely across our region for
much of the week with multiple chances of convection.  Some of this
convection could be strong to severe with bouts of heavy rainfall
possible.  Excessive rainfall could be problematic in some
areas...especially those that see repeated rainfall.

As the ridge axis is shunted south and west, we`ll see a return of
slightly cooler weather.  Have generally went below the SuperBlend
guidance here given that convection and convective debris will
likely have negative impacts on temperatures.  For now, have stuck
close to highs in the upper 80s to around 90 with overnight lows in
the lower 70s which is close to average for late July.

A look ahead into next weekend and into early August looks to
feature a return to a trough east, ridge west type pattern.  This
would keep the Ohio Valley in a cooler, but wet pattern as we enter
the new month.  Global teleconnection indices and organic mid-level
wave correlation methods generally support a return to this upper
level configuration.

&&

.AVIATION (18Z TAF Update)...
Issued at 100 PM EDT Sat Jul 23 2016

Cloud field early this afternoon would indicate the best chance for
storms in the near term to initiate west of Louisville, over
southwest Indiana, and along the KY/TN border. Clouds are fairly
flat over the KLEX terminal this hour. Cannot rule out isolated
storms at each site, but confidence now just high enough to mention
at KBWG. Storm chances will dissipate by mid evening and potentially
get replaced by more fog at KBWG (or any site that sees late
afternoon/evening precip). Otherwise, for Sunday, winds will start
to have a south to southwest component.

&&

.LMK Watches/Warnings/Advisories...
KY...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
     KYZ023>034-038-045-046-053-054-061>065-070>077-081.

IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
     INZ076>079-083-084-089>092.

&&

$$

Update.........RJS
Short Term.....MJ
Long Term......MJ
Aviation.......RJS



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