Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 162344
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
744 PM EDT Tue Jul 16 2019

...Updated Forecast and Aviation Discussions...

.Forecast Update...
Issued at 730 PM EDT Tue Jul 16 2019

Still have a couple of stronger cells moving east of I-65 this hour,
but in general the region has fared well with today`s moist
atmosphere. We still could see a wave or two of rains wrapping
around the remnant circulation of Barry into the night, so will keep
in good chances for showers along with a few rumbles of thunder.
Will send out an update shortly to remove the late afternoon wording
and reduce the thunder chances overnight.

&&

.Short Term...(This evening through Wednesday)
Updated at 330 PM EDT Tue Jul 16 2019

Afternoon satellite imagery reveals mostly sunny skies across much
of central and eastern KY.  Cloud cover has really been limited to
our far western counties where scattered convection has been moving
northeastward.  Temperatures ranged from the upper 80s in the sun
with 90-91 in the urban heat islands, to the upper 70s under the
clouds in western KY.

For the rest of the afternoon and evening, we will be watching the
remnants of tropical cyclone Barry move northeastward through the
region.  Overall convection looks to come in several waves this
afternoon.  First wave is pushing through southern IN at the moment.
Secondary wave is developing from near Evansville, IN southward into
western TN.  Atmosphere is modestly unstable with MLCAPE values in
the 1200-1500 J/Kg range.  There is a pocket of elevated effective
SRH stretching from Owensboro northeastward into our far NW CWA.
Overall surface flow remains rather unidirectional with some speed
sheer, but not really seeing much in the way of low-level backed
flow.  The combo of MLCAPE and effect SRH may pose an isolated
tornado risk over our far NW CWA over the next few hours.  However,
KLVX/KVWX Vrot values have been very low (20-25kt) and LCL heights
are still around 800-1000m.  Thus, probably going to see several
reports of funnel clouds with the strongest storms.

PWAT gradient was also seen across the region with values around 1.5-
1.7in across the Bluegrass region and then sharply rising to above 2
inches west of Evansville.  So storms out west of I-65 will be
capable of producing heavy rainfall.  Flash flood risk is certainly
there, especially where storms transverse over the same locations
repeatedly or train over the same swath of land.

Convective coverage should spread eastward into the I-65 corridor
later this afternoon and into the evening hours.  Just how far east
we`ll see it get is rather questionable.  Much of the high
resolution guidance keeps best chances of precipitation west of a
line from about Frankfort to Tompkinsville.  With that said, will
keep high PoPs out west of I-65 and tapering it to chance PoPs out
east.

Moving into the overnight hours, convection is likely to diminish in
coverage and intensity with the loss of heating.  We`ll probably see
some scattered showers and possibly a storm overnight, though the
best combo of moisture/instability looks to remain to our south.
Will maintain chance PoPs overnight, but will monitor trends this
evening and make further modifications as needed.  Lows will remain
mild with readings in the 70s.

For Wednesday, upper trough axis will shift to the east along with
the slug of tropical moisture associated with the remnants of Barry.
Best chances of storms on Wednesday will likely be across the
northeast half of the forecast area.  Highs will be in the mid-upper
80s in most areas with a few spots hitting 90 once again.

QPF amounts through the short term period will likely see basin
averages around an inch, though some isolated amounts of 2-3 inches
will be possible...especially in areas that see training of storms.
The isolated nature of the high amounts and relative high FFG values
across the region should preclude the need for a watch.  That is not
to say that isolated flash flooding in some areas could occur over
the next 24 hours.

.Long Term...(Wednesday night through Tuesday)
Updated at 345 PM EDT Tue Jul 16 2019

...Excessive Heat Possible for End of Week through Weekend...

Heights aloft begin rising Wednesday night behind the departing
wave. At least scattered showers and storms look to linger east of I-
65 into late Wednesday evening. A period of dry weather is then
likely for much of the area 06-12z Thursday morning. There is a weak
NW to SE oriented boundary that drifts east from western KY and
southern IL Thursday morning. 12z models show moisture pooling with
sfc dewpoints above 75 F along with a subtle wind shift. Before
substantial upper ridging can build overhead, this may be enough for
isolated convection on Thursday, particularly west of I-65 in the
morning hours. Coverage should remain limited with anticyclonic flow
aloft and poor mid-level lapse rates. It will remain very humid in
the wake of the current tropical remnants, however. Heat and
humidity will be oppressive. Afternoon highs will reach the upper
80s to mid 90s with maximum heat indices in the upper 90s to mid
100s.

Confidence in medium range guidance is fairly high in its depiction
of a 593-594 mid-level ridge building over the Lower Ohio Valley
Friday into Saturday. Afternoon highs should have no trouble
reaching the low to mid 90s both days with peak heat indices of 100-
110 degrees. Will highlight the heat and humidity in an SPS and the
HWO for now, but will likely need a Heat Advisory late in the week.

The chances for precip return Sunday into early next week. Upper
ridge will gradually retrograde westward, and a large northern
trough drops southeast over the Great Lakes and Northeast US. A sfc
cold front should drop south through the area in the Monday time
frame, so bumped up rain chances for early next week.

&&

.Aviation...(00Z TAF Issuance)
Updated at 740 PM EDT Tue Jul 16 2019

Broken lines of showers and few thunderstorms continue to move east
through southern Indiana and central Kentucky. These lines will
continue to have limited affects on the TAF sites. For the rest of
the evening into early night LEX could see a line of weak
storms/rain showers move through. Precipitation is weakening across
the area.

Think a line will develop around daybreak. This line will
sweep through all the TAF sites. HNB will likely see the line around
9z, BWG and SDF 11-12z, and LEX around 14-15z. Rain chances will
drop throughout the day tomorrow. Expect many changes in ceilings
with broken convection, ceilings will likely bounce around.

&&

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

$$

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


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